Full opinion text
SMITH, District Judge. This is a suit under the patent laws for ■the infringement of two patents; the one, No. 1,753,775, hereinafter referred to as ’775, issued on an application filed by the plaintiff on May 24, 1929; the other, No. 2,041,285, hereinafter referred to as ’285, issued on an application filed by the plaintiff on September 28, 1933. These patents, like those heretofore considered and discussed in the related suit, 57 F.Supp. 388, pertain to the manufacture of paper and cover improvements in the process of sizing the cellulose fibers of which papers are made, and, although cognate, must- be separately considered and discussed. The patents in suit cover further improvements on the art of sizing paper in the pulp, and particularly on the inventions defined in earlier patents to the plaintiff, Nos. 1,558,845 and 1,589,947. The patents and publications of the prior art discussed and considered in the related suit, including the patents there in suit, are relevant and material to the issue of validity here presented, but a repetitious discussion of them would seem to be superfluous. It is, therefore, suggested that a reading of the earlier opinion, hereinabove cited, will facilitate not'only a comprehension of the art but also a proper appraisal of the present patents. Patent No. 775 The invention of this patent is defined in claim 3 thereof, which is typical, as follows: “A method of sizing paper which consists in treating the paper making fibre with sulphate of alumina, allowing the fibres to absorb the alum” (sulphate of alumina) “until the pH of the solution is over 5, and then treating the surface of the astringent fibres with a solution of rosin size.” (Emphasis by the Court.) The other claims, which are quoted in the footnote, *define nothing more than specific variants of the same invention. The dissimilarity of the respective claims is not substantial, and is, therefore, not material to either the issue of validity or infringement. It is here urged by the patentee, as it was in the prosecution of his application for the patent, that the invention, as thus defined, is a specific improvement on the invention covered by an earlier patent to him, No. 1,-585,469. The invention of the latter patent is defined in claim 2 thereof as follows: “A method of sizing paper pulp, which consists in treating the fibers (while in the beater) with sulphate of alumina and adding a stream of size emulsion to the fibers (as they are entering the Jordan engine.”) (Parentheses by the Court.) It is obvious, upon a mere comparison of the quoted claims, that the inventions of the patents are identical in substance, g-xcept for the allegedly novel concept of maintaining the hydrogen ion concentration in the stock, the degree of acidity, within the defined limits. It is of persuasive significance that upon rejection of the claims in suit on the earlier patent, this concept was urged by the patentee as the only critical distinction. When the claims in suit are construed in the light of the prior art, as they must be, it is evident that the essence of the invention lies only in this allegedly novel concept of maintaining the hydrogen ion concentration in the stock, the degree of acidity, during the sizing operation, within the prescribed optimum, to wit, between 5.0 pH and 6.8 pH, the lower coefficient denoting the degree of highest acidity, and the higher coefficient denoting the degree of lowest acidity at which an effective size may be coagulated. The process of the said claims is otherwise old, the successive steps thereof, to wit, the introduction of the aluminum sulphate into the stock, thus effecting the acidification of the fibers and the surrounding solution, followed by the introduction of the rosin size emulsion, thus effécting the coagulation of the size, having been disclosed earlier not only by the patentee but also by others. This, it appears from the cited references, was common practice in many paper mills long prior to its disclosure by the patentee. It follows that the ultimate issue presented for determination is whether or not the embodiment of this allegedly novel concept —conceived by others whose disclosures preceded that of the patentee, as will presently appear — in a process otherwise old, is such an advance over the prior art as will support the claim to patentable invention. It is our firm conviction, based upon the reasons hereinafter expressed, that it is not. State of the Art The art of sizing paper in the pulp, as practiced in the modern paper mill, was discovei-ed and disclosed by Moritz Illig in 1807. This art, although not immediately accepted generally, has been in common use without substantial modification since 1880, when the manufacture of paper from wood pulp was found to be commercially feasible. The development of this art, consistent with the progress of the paper industry, has been marked by numerous improvements on the method of application but by few modifications of the chemical process. It is significant that the improvements on the chemical process, including that of the patent in suit, have been minor, despite extensive study and numerous explanations of the sizing phenomenon. The methods of application, as distinguished from the chemical process, and the pertinent improvements thereon, were adequately considered and explained in the .opinion filed in the related suit. The present discussion is limited, so far as it is reasonably possible, to the chemical process, the applied chemistry of the art, to which the patent in suit is particularly and primarily directed. The chemical process is one in the practice of which the hydrated cellulose fibers, suspended in a water medium, are so treated as to overcome their absorptive quality and impart to the finished paper its water repellent property. The chemical ingredients, aluminum sulphate (the coagulant) and rosin emulsion (the size), are successively introduced into the stock in the course of its preparation and as it flows to the paper machine. The resulting chemical reaction, properly controlled, produces a colloidal gel of aluminum resínate and rosin, which is adsorbed by the cellulose fibers. The water of suspension is removed in the final operation, felting and drying, and the rosin size is tints rendered permanent, imparting to the finished paper its water repellant property. The chemical reaction is progressive and complex but for our present purpose may be sufficiently explained as follows: The solution of aluminum, sulphate, an acid solution having a pH value of approximately 3.5 to 4.0, coagulates the rosin emulsion, an alkaline “solution” having a pH value of approximately 8:0 to 9.0, thus producing the colloidal gel of aluminum resínate and rosin, which, as heretofore explained, is adsorbed by the hydrated cellulose fibers. This adsorption, the ultimate sizing reaction, heretofore described in footnote 13, is ascribed to the colloidal properties of the components, the hydrated cellulose fibers and the gel. The described chemical reaction is influenced by several factors, such as beating, temperature, etc., but it is necessary to consider here only the one to which the claims in suit are particularly directed, the hydrogen ion concentration in the stock, the degree of acidity. The rosin emulsion is efficiently coagulated, producing the colloidal gel essential to the ultimate sizing reaction, only if the optimum of acidity, to wit, within the range of 4.0 pH and 6.8 pH, is maintained in the stock throughout the reaction. It should be noted, however, that the ultimate sizing reaction, the adsorption of the colloidal gel by the cellulose fibers, is not influenced, except in efficiency, by the sequence in which the chemical ingredients are introduced into the stock. The same reaction occurs either upon the introduction of the aluminum sulphate into the stock, previously treated with rosin size emulsion, or upon the introduction of the rosin size emulsion into the stock, previously treated with aluminum sulphate. The latter practice, embraced in each of the claims in suit, was followed in the industry for many years prior to the present invention, and was disclosed by the patentee in an earlier patent, No. ’469. It is apparent from the cited references that local mill conditions are frequently determinative of the practice. Prior Art Thus far we have considered and explained the chemical process in the light of after-acquired knowledge — that is, knowledge acquired since 1807, the year of Illig’s discovery, but prior to 1929, the year of DeCew’s alleged discovery — in an endeavor to facilitate a proper understanding of the purported invention and a due appreciation of the prior art references hereinafter summarized and discussed. We now turn to a consideration and discussion of the earlier disclosures, from which it clearly appears that the patentee’s contribution to the art, if any, does not transcend the common knowledge and skill of the art, the test of patentable invention. It was common knowledge long prior to the present invention that the coagulation of the sise, as distinguished from a mere precipitation of rosin on the cellulose fibers, was essential to the ultimate sizing reaction, the adsorption of the colloidal gel of aluminum resínate and rosin by the hydrated cellulose fibers. It was likewise common knowledge that an excessive degree of acidity in the stock impaired or destroyed the colloidal gel, producing instead a flocculent precipitate, thus affecting the efficiency of the ultimate sizing reaction. The known methods of controlling the acidity in the stock, as well as the known methods of measuring the degree of its intensity, were, however, crude and inadequate. These conclusions, adequately supported by numerous references, are not disputed. It would be error to assume that the paper industry had failed, until the advent of the present invention, to recognize the importance of acidity control. It was common practice to maintain the acidity of the stock within efficient limits, although the lack of an adequate scientific method of determining the limits made it difficult to define the optimum with certainty. Under the earliest control method the sizing result, observed as the stock flowed to the paper machine, was determinative of the optimum; the maintenance of an efficient optimum was contingent upon the skill of the operator. It would seem that the paper industry, even in its earliest stages, lacked only a scientific 'method of determining the degree of acidity in the stock and defining its limits with accuracy. It may be reasonably inferred that even under the earliest practice the hydrogen ion concentration in the stock, the degree of acidity, was maintained within the range of 4.5 pH and 6.5 pH. There is now conclusive proof that the size could not have been coagulated and an efficient sizing reaction thus produced unless the hydrogen ion concentration was maintained within this range; if the acidity of the stock fell below 6.5 pH (tending toward alkalinity), the rosin size would not have been coagulated but would have remained in suspension in the emulsion, and, if the acidity of the stock rose above 4.5 pH (tending toward excessive acidity), the colloidal gel, admittedly essential to the ultimate sizing reaction, would have been impaired or destroyed, producing a flocculent precipitate. The discovery of a method of maintaining the hydrogen ion concentration within predetermined limits, and its subsequent adoption by the industry, undoubtedly contributed to the efficient application of the sizing process, but the process remained unchanged. It appears from the cited references that prior to the present invention extensive studies of the sizing process were made by those who preceded the patentee. These studies were directed to the problem of controlling the hydrogen ion concentration in the stock during the sizing reaction and led to the discovery of control methods which were readily adaptable to the sizing pr-ocess. The results of these studies were widely published, and a fund of pertinent knowledge was available to the patentee when he entered the field in 1929. The apposite publications are worthy of special consideration. Beltzer, The Sizing of Paper, published in 1924. This article emphasizes the importance of maintaining the hydrogen ion concentration of the stock within predetermined limits and recommends a simple method of control which has been superseded by the scientific methods hereinafter considered. It is therein recommended: Page 843. “The hydrogen ion concentration of the stock as it reaches the wire (should) he so low that, even if no size were added, it could not affect the indica-tor usually employed, namely, litmus test paper.” Page 843, “In practice, sizing is largely controlled by means of litmus test paper. It has been observed that in order to have a properly-sized sheet, the water should be very slightly acid to litmus when it reaches the machine wire. If the litmus does not redden even slightly after a minute, that is, if the water is neutral, the paper is practically unsized; and if the water has an alkaline reaction the paper is as porous as blotting paper. On the Other hand, if the test paper reddens too quickly, the stock is too acid and the sizing will be defective; but the results will not be as bad as in the case of a neutral or of an alkaline reaction.” (Emphasis by the Court.) This disclosure, if it is to be accorded its full significance, must be appraised in the light of that which was common knowledge to the skilled technician, to wit, that in the interpretation of the color change, blue to red, the degree of acidity is reflected in the intensity of the color and the rapidity of the reaction. If the hydrogen ion concentration of the stock, as it reaches the wire, is so low that it will not affect the indicator, the acidity of the stock must be below 6.5 pH and nearer 7.0 pH, the point of neutrality; if the hydrogen ion concentration of the stock is so high that the indicator “reddens too quickly,” the acidity of the stock must be above 4.5 pH and nearer 4.0 pH. The predetermined limits of acidity, although not defined by Beltzer in terms of pH values, coincide with the transition range of the indicator, that is, within the approximate limits of 4.5 pH and 6.5 pH. The relevancy of this reference may be challenged on its failure to define the optimum of acidity with accuracy. However, it is our opinion that this failure does not detract from the significance of the disclosure, especially where, as here, its teachings are clear to the person skilled in the art. Thiriet and Delcroix, Electric Theory of Rosin Sizing, published in 1924. These writers, without asserting any claim to original discovery, concede that the efficiency of the ultimate sizing reaction is influenced by the hydrogen ion concentration in the stock, the degree of acidity, and emphasize the importance of maintaining the hydrogen ion concentration in the stock within predetermined limits, approximately 4.5 pH to 5.5 pH. The relevancy of the articles, aside from the theory of sizing therein advanced in support of its teaching, lies in the following disclosures: Page 54, et seq. “But in connection with these particularly convincing results we wish to say a word as to the method of applying our theory to the control of sizing in paper mills. The actual control method must be very carefully chosen, as otherwise disappointment is almost bound to follow. The results which we have given above were obtained only at the expense of a very close and careful control of operations. “Various methods can be used: preliminary neutralization of the raw water with acid, substitution of sulphuric acid for part of the aluminum sulphate, direct addition of sulphuric acid in the beaters, etc. Each case should be carefully studied and treated according to the particular conditions prevailing. But whatever procedure be adopted, the principle of the method remains the same — namely, to adjust the hydrogen ion concentration of the pulp suspension as near as possible to the optimum value for sizing. “We make use of two colored indicators, methyl red and sodium alizarin-sulphonate, which have opposite color changes, the one from yellow to red and the other from red to yellow. When the back water from the paper machine gives practically the same color with both indicators, the pulp suspension has the proper pH. If the methyl red is redder than the sulphoalizarin, the stock is too acid, while if the methyl red is yellow the pulp is too alkaline. The test is so simple that it can easily be carried out by the machine tender. Its two chief advantages, besides its simplicity are: “(1) The pH range over which sizing is possible is much wider than that over which the two indicators give approximately the same color. Consequently, any appreciable variation in the pH is detected-long before the danger point is reached, and conditions can be corrected in time to avoid defective sizing(Emphasis by the Court.) These writers recommend, as does Beltzer, that the hydrogen ion concentration in the stock, the degree of acidity, be maintained within predetermined limits. These limits, although not defined in terms of pH values, are fixed with certainty by the transition range of the respective indicators. The average mill operator, possessing nothing more than the expected knowledge and skill, can follow the teachings of the disclosure without difficulty. The degree of acidity in the stock at the “paper machine,” at which point the sizing reaction has progressed to completion, is indicative of the hydrogen ion concentration in the stock at the time of the sizing reaction; it is obvious that the pH reading at this point has no other significance. It is evident, if the teaching of this reference is properly interpreted and accorded its full significance, that the hydrogen ion concentration conducive to an efficient sizing reaction is within the approximate range of 4.5 pH and 5.5 pH. This conclusion is supported by a later disclosure. Thirict and Delcroix, The Technique of the Use of Rosin Size in Paper Making, published in 1926. Page 393. “The authors propose the following theory for explaining the mechanism of sizing: Over a certain range of hydrogen ion concentration, pH, the cellulose and rosin have electric charges of opposite signs, so that the positive rosin and negative cellulose are nmlually attracted, and sizing is possible; outside of this range, the electrolyte is too acid or too basic, the cellulose and rosin have charges of the same sign and repel each other, so that sizing is impossible.” (Emphasis by the Court.) Page 394. “We have shown on a previous occasion that the rosin particles are held by the cellulose fibers because of electric charges of opposite signs on the surfaces of the two substances when the hydrogen ion concentration of the stock, as expressed by the pH, lies betzveen certain limiting values. This attraction prevents the rosin being carried away by the water that drains through the paper machine wire; and at the driers, the size is permanently fixed to the fibers by fusion.” Page 394. “However, if we admit that the elementary constituents of matter are the negative electron and the hydrogen ion, it is easy to understand that the pH of a liquid exerts considerable influence on the equilibrium of the constituents of the solid immersed in it, that is, on the surface contact charge. We have determined experimentally, and verified in the mill, that very good results were obtained when the pH of the stock zms kept in the neighborhood of 5.0 to 4.5.” (Emphasis by the Court.) The particular relevancy of the reference lies in the specific teaching that the size may be coagulated and an efficient sizing reaction thus produced only if the hydrogen ion concentration in the stock, the degree of acidity, is maintained within a predetermined range, preferably “in the neighborhood of 5.0 and 4.5” pH. The theory upon which this teaching is predicated need not concern us. It should be noted that the writers, although recommending that the degree of acidity in the stock be maintained within the range of 4.5 pH and 5.0 pH, do not assert that this optimum is critical. It is conceded that the size may be coagulated and an efficient sizing reaction thus produced within a wider range; the only warning is against any “appreciable variation” which would affect the efficiency of the ultimate sizing reaction. This teaching is in agreement with later disclosures. Shaw, Hydrogen Ion Concentration in the Paper Mill, published in 1925. Shaw, an associate technologist in the Bureau of Standards, demonstrated and proved by a series of experiments that the efficiency of the ultimate sizing reaction was influenced by the hydrogen ion concentration in the stock, the degree of acidity, and that this efficiency increased with the hydrogen ion concentration until the maximum of the optimum, approximately 4.6 pH, was attained. The results of these experiments are extensively reviewed in the cited reference. It is therein disclosed that an effective size is coagulated if the degree of acidity in the stock is maintained within the range of 4.6 pH and 5.4 pH. It is urged by the patentee that in the Shaw experiments the hydrogen ion concentration in the stock at the time of the sizing reaction was below 4.0 pH. This, however, is clearly not the fact. The highest degree of acidity produced in “machine runs” 2 and 3 was 4.6 pH, and this was produced upon the introduction of the aluminum sulphate into the stock at the beater; the lowest acidity produced was 5.4 pH, and this was produced at the machine chest as the reaction neared completion. It is evident that the optimum is within these limits. The writer expresses the opinion “that considerable economy in the use of alum and better control of the paper-making processes would be effected if an optimum degree of acidity were determined and observed in the mill.” It is not mere coincidence that the patentee likewise claims for his invention “economy in the use of alum.” Taylor, The Application of Hydrogen Ion Control to the Manufacture of Pulp and Paper, published in 1926. This is a comprehensive treatise in which the writer, after emphasizing the importance of hydrogen ion control in the manufacture of paper, recommends a control method which is practiced in many paper mills. Its relevant disclosures follow: Page 38, et seq. “The point in the paper making process at which control of acidity is of the greatest importance is, however, in the precipitation of the sizing. The water which is used in paper manufacture is in most cases alkaline. The reaction of the pulp will of course affect this reaction but, if the pulp is neutral, the natural alkalinity of the water is increased by the addition of the sizing agent which is usually rosin, this being added in the form of an alkaline rosin soap. This additional alkalinity will of course depend on the percentage of free rosin in the sizing. “It has long been known that the stock should be 'slightly acid’ during a part of the beating and at the time of delivery to the paper machine. This acidity is usually obtained by the addition of alum, which also precipitates the sizing. ‘Slightly acid’ is a very indefinite term which varies enormously, depending on the method of testing and on the meaning of the term to various operators. If the stock is too nearly alkaline, the sizing will not be completely and efficiently precipitated. On the other hand, additional alum over that necessary for precipitation of the sizing, adds to the cost of manufacture and has a harmful effect.” (Emphasis by the Court.) This writer recommends colorimetric control of the hydrogen ion concentration. It seems unnecessary to review this method except to note that in its application the transition ranges of certain color indicators are determinative of the limits of acidity. The indicators are compared with standardized colors of known pH value, and the hydrogen ion concentration, or pH value, is reflected in the “comparative reading.” Taylor, Control of Acidity and Alkalinity in the Manufacture of Paper, published in 1927. This article contains a brief summary of the writer’s earlier discussions. The pertinency of the article, however, resides in the following disclosure: Page 1145. “It is impossible to give any optimum pH value for the sizing operation, as this value is affected by many different factors. It is known that some mills obtain best results at pH values ranging from 4.2 to 5.4 but (it) is necessary for each mill to determine its own optimum. After this is done, it is a simple matter to maintain this optimum continuously.” (Emphasis by the Court.) Roschier, The Importance of Hydrogen-Ion Concentration in the Sizing of Paper, published in 1928. This is such a comprehensive treatise on the subject that we find it difficult to quote from it without detracting from the full import of the teachings of the writer. The apposite disclosures follow: Page 640, “In time this theory was both amplified and criticized, and the Frenchman Orioli published a most interesting criticism as a result of experiments carried out in 1848. The most important parts of his work is given in Hoffmann’s treatise. Orioli showed that fibers have such a strong affinity for aluminum salts that the latter cannot be removed by washing. He treated fibers with d solution of alum, removed the excess of solution, and with the fibers prepared in this manner, he obtained a rosin sized sheet of very good quality using but a third of the amount of alum that was then considered necessary to obtain the same degree of sizing.” (Emphasis by the Court.) Page 640. “The interesting work of Orioli, which was carried out in the early days of the practical application of rosin sizing, has been used as a starting point by numerous later investigators who tried to develop a satisfactory theory of sizing. Some of his claims were subsequently confirmed.” Page 680. “Quite recently, Oman stated that the presence of alum was of secondary importance, provided the fibers had previously been treated with alum to give them a positive charge. He arrived at this conclusion as a result of experiments, in the course of which, he treated cellulose with alum, washed the fibers to remove the alum that had not been adsorbed, and then obtained a perfectly sized sheet by the action of colloidal free rosin, without addition of alum, on the fibers that had been thus treated. Oman repeated his experiments with both bleached and unbleached pulp, and he always obtained a properly sized paper.” (Emphasis by the Court.) Page 715. “The amount of alum used varies considerably in different mills, depending on local conditions, such as the hardness of the raw water, composition of the size, acidity of the pulp, fillers, etc. Many investigators, among whom may be mentioned Lorenz, claim that nearly all the aluminum that takes part in the sizing is adsorbed by the fibers; others on the contrary, including Aschan, consider, that, roughly, two-thirds of the alum remains in the back water.” (Emphasis by the Court.) It is apparent that this is a complete disclosure of the successive steps of the purported invention, to wit, “treating the paper making fibers with sulphate of alumina, allowing the fibers to absorb the alum * * and then treating the surface of the astringent fibers with a solution of rosin size.” (Claim 3 of ’775.) It is equally apparent that the principle advanced by the patentee in support of his claim to invention is identical with the principle discovered by Orioli and later proved by Oman’s experiments. The Roschier article continues: Page 717. “Those who are accustomed closely to follow the sizing operation in the mill, know that the stock frequently has a pH value of 5.5 when it reaches the paper machine, and yet the paper is properly sized. In kraft paper mills, sizing is often carried out at a very low acidity (pH value of 5.8), and very good sizing is obtained with a small amount of rosin.” (Emphasis by the Court.) Page 746. “When fibers are sized with rosin and alum at an acidity corresponding to a pH value of 5.5 a well sized sheet is obtained. At this acidity, nearly all the combined rosin of the size milk is converted into aluminum resínate, which is difficultly soluble, and which is practically not ionized.” Roschier demonstrated and proved by a series of experiments, as had Shaw, that the efficiency of the ultimate sizing reaction is influenced by the hydrogen ion concentration in the stock, the degree of acidity, and that this efficiency increased with the hydrogen ion concentration until the maximum of the optimum, approximately 4.5 pH, is attained. Roschier declared his preference for a hydrogen ion concentration of approximately 5.2 pH, but expressed the opinion that the optimum of acidity conducive to an efficient sizing reaction is within the range of 4.5 pH and 5,5 pH. The conclusions of this writer are briefly summarized by him as follows: Page 747. “We have already explained how aluminum resínate is partly decomposed into free rosin in very acid medium. It is generally considered that this fact is favorable to sizing. * * *. In the experiments described earlier in this paper, we showed that at a pH value of 4.5, nearly all the sodium resínate is converted into aluminum resínate. Fig. 4 now shows us that under such conditions, free rosin is not as good a sizing agent, but that on the contrary, sizing is better at a pH value of 5.2 when the rosin is entirely in the form of aluminum resínate. The better sizing obtained in this case is not due to the larger amount of aluminum resínate present, but rather to the fact that a high H' ion concentration reduces the degree of dispersion of the particles taking part in the sizing, and also partly neutralizes their negative charge. * * *. When, * * *, the acidity is lower, aluminum compounds are formed and adsorbed by the rosin, and the latter in turn by the fibers. These compounds hold the rosin mechanically in contact with the fibers. It will be recalled that Orioli claimed that these compounds themselves possessed considerable sizing power. “In weakly acid solution, rosin remains in suspension for a long time after it has flocculated, which means that the rosin forms a positively charged adsorption compound with aluminum hydrate; while at a pH value of, say 3.7, it flocculates and rapidly rises to the surface. This fact is of decided importance in sizing. The better the suspension of t.ie rosin the more easily does it come into contact with the fibers producing a better sizing. On the other hand, the higher the acidity and the further the reaction of the medium from the isoelectric point of ceUulose, which is at a pH of about 6.0, the poorer the sizing. Moreover, we have shown on other occasions that cellulose is more rapidly beaten at a low acidity, and it has been known for a long time that well beaten pulp is easier to size than one that is less beaten.” (Emphasis by the Court.) The pertinent teachings of Roschier may be briefly summarized as follows: First, a low degree of acidity in the stock, within the limits of 4.5 pH and 5.5 pH, effects a coagulation of the rosin size, thus contributing to the efficiency of the ultimate sizing reaction; second, a high degree of acidity in the stock,. 4.0 pH or below, effects a precipitation of the rosin size, thus impeding the ultimate sizing reaction; and, third, the optimum of acidity conducive to an efficient sizing reaction is within the range of 4.5 pH and 5.5 pH. These teachings would seem to embrace the allegedly novel concept of the patentee. Britton, Hydrogen Ions, Their Determination and Importance in Pure and Industrial Chemistry,. published in 1929. This monograph is pertinent because of the writer’s evaluation of Roschier’s disclosures. The criticisms are so clear and unambiguous that we quote them without comment: Page 410, et seq. “The rosin size contains an excess of free rosin to an extent of from 15 to 25 per cent. * * *. Sizes prepared with the aid of ‘atomisers’ may, however, contain as much as 40 to 45 per cent, of free rosin. These sizes are added to the half-stuff in the ‘beater’ during the last half of the beating process and then by the interaction with a solution of aluminum sulphate added either previously or subsequently, liberates rosin and alumina upon the surfaces of the fibres, and so cements them together. A well-known book on paper technology suggests that ‘the order of adding the sizing agents appears in many cases to have but little influence on the final result/ but goes on to say that ‘in many mills it is customary to add a portion of the alum to the beater before running in the diluted size.’ The actual sizing operations should be carried out between pH 3.9 and 5.5 (cf. Roschier, Pappers och Travarutidskrift, 1927, 154), and for this reason it seems probable that the addition of a part at least of the aluminum sulphate before adding the size is beneficial, for in redacting with any alkali left in the pulp it will tend to precipitate aluminum hydroxide, and this is known to begin to take place at pH 4.0 to 4.1 (Britton, J. Chem. Soc., 1925, 127, 2120). Roschier states that sizing does not take place below pH 3.9, which is evidently partly due to the fact that aluminium hydroxide is then under normal conditions not precipitated. Moreover, the rosin in the size begins to flocculate at about pH 3.7 and to rise to the surface of the solution. The ideal condition is to get the rosin in the size into a very fine suspension, so that it can be readily and evenly deposited upon the fibres. Too much acid increases the size of these particles and therefore gives rise to an irregular and defective sizing. * * *. Actually, however, visible precipitation does ensue on account of the fact that the rosin passes first into a highly dispersed colloidal solution. Precipitation oecurs at about pH 3.7. The transition from the disperse phase to the precipitate which occurs with decreasing pH is accompanied evidently by an increase in the size of the colloidal particles, which coagulate as soon as they have acquired the magnitude requisite to stop the Brownian movement which tended to keep them in colloidal suspension. Hence as Roschier states, the most satisfactory sizing conditions obtain at about pH 5, when the particles have become of the dimensions suitable for efficient sizing. It will be observed that this pH lies about midway between the two extremes. Another advantage which is obtained by adding some aluminium sulphate before sizing, is that it sets up automatically a pH (about pH 4) and so prevents the precipitation of the curdy calcium resinates which are formed in alkaline solutions that would impair the sizing.” (Emphasis by the Court.) Page 412, et seq. “Much controversy has taken place as to the actual mechanism of rosin sizing, whether the sizing is due to aluminium resinate, or to rosin alone, or to rosin in conjunction with alumina. The fact is that both alumina and resin are deposited on the fibres, but the query arises when the condition is considered. The theory of sizing is of practical importance, for when the constitution of the material deposited on the fibre surface has once been established, it then will become an easy matter to find the optimum pH conditions for sizing. It cannot be merely a, coincidence that the pH for sizing should be above pH 4 and should preferably be about pH 5. * * *. In a sizing process taking place above pH 4, it is unlikely that any aluminium resinate would be contained in the precipitate on account of the hydrolysing action which would then take place. If combination occurred between such a weak acid and a weak base by virtue of the insolubility of the salt produced, then that salt would be precipitated from solutions more acid than pH 4, and would undergo decomposition as soon as the pH of the mother-liquor exceeded 4 (cf. Britton, J.C. S., 1925, 127, 2146). Roschier’s contention that basic aluminium resinate is produced at pH’s below 4.5 appears therefore to be probable, but it is improbable that aluminium resinate, * * *, is formed at pH 5, and for. that reason should give rise to best sizing. That this should be the pH requisite for efficient sizing is probably due to the fact that aluminium hydroxide then attains enhanced insolubility and therefore becomes more firmly fixed to the fibres. * * *_ Whatever the true explanation may be, sulphate is always found in the sized paper, so also is resin in the free state. Roschier recommends the range pH 3.9 to 5.5 for sizing ordinary paper, and pH 5.8 for the sizing of kraft paper, which requires the minimum amount of resin. From what has been said it seems feasible to consider sizing as being effected by the fixing to the pulp fibres of highly basic aluminium sulphate, free rosin, and perhaps a little basic aluminium resinate.” (Emphasis by the Court.) Joachim, Hydrogen-Ion Concentration, published in 1928. This is a comprehensive treatise on the subject of hydrogen ion control in the manufacture of paper. It is therein disclosed that the concept of maintaining hydrogen ion concentration in the stock, the degree of acidity, within predetermined limits, was common knowledge, and that the practice was in public use in many paper mills. We quote only the apposite disclosure: “The importance of hydrogen-ion control in engine sizing is now generally realized by the paper industry. It has long been known that the stock as it goes to the machine, and the white water as it leaves the wire, should be acid, in order to get perfect operation, but no definite data regarding this acidity were available. The ratios of alum to size varied from mill to mill, some using as much alum as 5 times the weight of the size, while others obtained satisfactory results with equal amounts of size and alum. * * *. By aid of hydrogen-ion measurements, it has been definitely established that, in the majority of these cases, almost unbelievable amounts of alum had been wasted, and that by judicious adjustment of the pH value of the stock and the white water, and better washing of the stock before reaching the beaters, considerable savings could be effected. The optimum pH for sizing will, to. a-greater or less extent, always depend on local conditions. The optimum pH for.precipitation of aluminum ions in. pure solutions is about 5.0 to 5.5; however, this does not necessarily mean optimum .sizing- results, In some mills, the stock is adjusted to pH 4.5; others are getting satisfactory waterproofing with a pH of 5.8 to 6.0 in the beater; while some have as low as 3.5. No definite rules concerning this practice can be laid down, but local conditions and the grades of paper being made will determine the degree of acidity to be maintained." (Emphasis by the Court.) This last reference, although not in evidence, is from an encyclopedic work, available in many public libraries, and is, therefore, one of which the Court may take judicial notice. Werk v. Parker, 3 Cir., 231 F. 121, affirmed 249 U.S. 130, 39 S.Ct. 197, 63 L.Ed. 514. However, we reserve to the plaintiff the right, if he deems it necessary, to either challenge the reference or controvert its disclosure. Lack of Invention It is evident that the disclosure of the patent in suit, examined in the light of the prior art and measured by commonly accepted standards, does not surpass the common knowledge of the art but arises from it as the consequence of its normal and expected development. The operative principle of maintaining the degree of acidity in the stock within limits conducive to an efficient sizing reaction was old, as were the successive steps of the purported invention. It seems reasonably clear that the only obstacle to the' efficient application of this principle, even in the earliest practice of the art, was the lack of a suitable method of determining these limits with accuracy. This obstacle was removed by the invention of adequate control methods which made possible the accurate evaluation of the hydrogen ion concentration in the stock, the degree of acidity — an invention to which the patentee can assert no claim. The invention of the patent in suit followed the disclosure of these control methods, as did other similar improvements in the process, but as a consequence of a normal development of the art and not as a result of a departure from the well-chartered course. There is, therefore, no patentable invention in the disclosure of the patent in suit. Hansen v. Slide, 3 Cir., 230 F. 627, 632; Atlantic Refining Co. v. James B. Berry Sons Co., 3 Cir., 106 F.2d 644, 655, certiorari denied 311 U.S. 657, 61 S.Ct. 12, 85 L.Ed. 421; Electric Vacuum Cleaner Co. v. P. A. Geier Co., 6 Cir., 118 F.2d 221, 224, and other cases hereinafter cited. It is apparent from our study of the history of the art and its development that the patentee was not the first ,to either recognize the problem or conceive the remedy. It was known long prior to the present patent that an excessive degree of acidity in the stock was destructive of the colloidal gel essential to the ultimate sizing reaction, and it was likewise known that this potential destruction could be overcome by the simple expedient of maintaining the degree of acidity in the stock within limits conducive to proper coagulation. The only-obstacle to the progress of the art, as heretofore stated, was the lack of suitable methods of control. The earlier methods were crude and failed to meet the exacting requirements of the art, and the paper industry demanded more efficient methods, consistent with its progress. This demand was met as early as 1924, if not earlier, by the invention and disclosure of adequate control methods peculiarly adaptable to the sizing process. Their subsequent adaptation, a course plainly recommended, and the only contribution to the art to which the patentee can successfully lay claim, required nothing more than the expected ingenuity of the persons skilled in the art. It has been repeatedly held that such an adaptation, requiring nothing more than common knowledge and skill of the art, is not invention. It is .conceded by the patentee that the essence of his invention, as heretofore stated, resides in the allegedly novel concept of maintaining the degree of acidity in the stock, during the sizing reaction, within the exact range defined in the respective claims of the patent. The claim to patentable invention rests solely on this operative principle, which the patentee contends patentably distinguishes his disclosure from those of the prior art. We cannot agree with this contention. The concept is obviously not novel. The cited ref erenees of the prior art disclosed not only the operative principle of maintaining the degree of acidity in the stock within predetermined limits conducive to an efficient sizing reaction but also an adequate method of determining these limits with accuracy. The prior art was, in fact, replete with such disclosures when the patentee entered the field. The ascertainment of the optimum of acidity — the alleged “discovery” upon which the patentee predicates his claim to patentable invention —required nothing more than routine experimentation, a course plainly indicated by the prior art and admittedly followed by the patentee. This does not constitute “invention” within the meaning of the statute, especially where, as here, the experimentation followed the teachings of the prior art and required nothing more than the expected knowledge and skill of the art. Standard Brands v. National Grain Yeast Corporation, 3 Cir., 101 F.2d 814, affirmed 308 U.S. 34, 60 S.Ct. 27, 84 L.Ed. 17; Ruben Condenser Co. v. Aerovox Corporation, 2 Cir., 77 F.2d 266, certiorari denied 296 U.S. 623, 56 S.Ct. 145, 80 L.Ed. 443; Fink v. V. Foscato, Inc., 2 Cir., 79 F.2d 842; Ruben Condenser Co. v. Copeland Refrigeration Corporation, 2 Cir., 85 F.2d 537; Hamilton Laboratories v. Massengill, 6 Cir., 111 F.2d 584, certiorari denied 311 U.S. 688, 61 S.Ct. 65, 85 L.Ed. 444; Naamlooze Venootschafs, etc., v. Coe, 76 U.S.App.D.C. 313, 132 F.2d 573; Wallace v. F. W. Woolworth Co., 2 Cir., 133 F.2d 763, certiorari denied 320 U.S. 739, 64 S.Ct. 40; Libbey-Owens-Ford Glass Co. v. Celanese Corporation, 6 Cir., 135 F.2d 138, certiorari denied 320 U.S. 744, 64 S.Ct. 46. The purported discovery of an optimum of acidity, within permissible limits previously recognized and admittedly not critical, does not enhance the clai-m to patentable invention. It has been held that such a discovery is not a patentable “discovery” within the meaning of the statute. DeLamar v. DeLamar Min. Co., 9 Cir., 117 F. 240; Brady Brass Co. v. Ajax Metal Co., 3 Cir., 160 F. 84, certiorari denied 210 U.S. 433, 28 S.Ct. 762, 52 L.Ed. 1136; Bethlehem Steel Co. v. Churchward International Steel Co., 3 Cir., 268 F. 361, certiorari denied 255 U.S. 572, 41 S.Ct. 376, 65 L.Ed. 792; Bellis Heat Treating Co. v. Heatbath Corporation, 1 Cir., 23 F.2d 239; Kwik Set v. Welch Grapejuice Co., 2 Cir., 86 F.2d 945; American Lecithin Co. v. Warfield Co., 7 Cir., 128 F.2d 522. This is particularly true where, as here, the principles of investigation being known, the purported discovery followed routine experimentation along the lines previously disclosed. Id. The invention of the respective claims in suit, appraised in the light most favorable to the patentee, embodies nothing more than an obvious combination of old elements. These elements had been in common use long prior to the advent of the patent, singly and in combinations similar to, if not identical with, those defined in the claims. Such combinations, in the absence of new and useful results, do not rise to the dignity of patentable invention. Bauer Bros. Co. v. Bogalusa Paper Co., 5 Cir., 96 F.2d 991; Standard Brands v. National Grain Yeast Corporation, supra; Grosjean v. Panther-Panco Rubber Co., 1 Cir., 113 F.2d 252; Dorr Co. v. Yabucoa Sugar Co., 1 Cir., 119 F.2d 521; Floridin Co. v. Attapulgus Clay Co., 3 Cir., 125 F.2d 669; Dow Chemical Co. v. Halliburton Oil Well Cementing Co., 6 Cir., 139 F.2d 473, certiorari granted 322 U.S. 719, 64 S.Ct. 1145. The complete absence of invention seems to be further established by the conclusive evidence that persons other than the patentee, pursuing independent study and research, conceived a solution of the problem identical in substance with the one herein urged by the patentee in support of his claim to patentable invention. Julius Kayser & Co. v. Rosedale Knitting Co., 3 Cir., 98 F.2d 839, certiorari denied 305 U.S. 649, 59 S.Ct. 230, 83 L.Ed. 419; Himmel Bros. Co. v. Serrick Corporation, 7 Cir., 122 F.2d 740; Hazeltine Corporation v. General Motors Corporation, 3 Cir., 131 F.2d 34. This is competent proof, if further proof were needed, that the alleged discovery derived from the common knowledge of the art as a direct consequence of its development. Ibid. Those who preceded the patentee expressed a difference of opinion as to the optimum of acidity, but this is not material. All of them, having disclosed the principle, conceded that an optimum of acidity, although more efficient, was not critical, provided, of course, that its range was well within the permissible limits of 4.0 pH and 6.5 pH. The pertinent disclosure of the patent differs from those of the prior art only in the range of the optimum therein defined. This is a trivial difference, involving nothing more than a change of degree, and is obviously insufficient to support the claim to patentable invention. It may be conceded, for the purpose of present discussion, although the evidence does not support the concession, that the patentee’s contribution is a “decided improvement” over the prior art. This fact, however, in the absence of equally important facts, will not support the claim to patentable invention. In the case of Hansen v. Slick, supra, 230 F. at page 633, the Circuit Court of Appeals for the Third Circuit stated: “Substantial advance, marked improvement, progressive steps in an art, however beneficial, are not in themselves evidence of invention. They áre to be expected, and, as the art progresses, more engineering skill, more mechanical progress, but less invention, are naturally to be looked for. It is when skill and progress stop abreast of an obstacle that inventive genius intervenes and invents.” These principles seem to be particularly applicable here. . It is the opinion of the Court that the claims in suit are so broadly drafted as to completely embrace an art which had been in common use in the paper industry long prior to the advent of the patent. These claims, if held valid, would enable the patentee to arrogate to himself a monopoly not contemplated by the patent laws, a monopoly which would stifle the normal development of the art as well as the progress of the paper industry. The manufacturer would be relegated to the use of inefficient methods which had been outmoded long prior to the advent of the patent. “The design of the patent laws is to reward those who make some substantial discovery or invention, which adds to our knowledge and makes a step in advance in the useful arts. Such inventors are worthy of all favor. It was never the object of those laws to grant a monopoly for every trifling device, every shadow of a shade of an idea, which would naturally and spontaneously occur to any skilled mechanic or operator in the ordinary progress of manufactures. Such an indiscrimina' : creation of exclusive privileges tends rather to obstruct than to stimulate inventions. It creates a class of speculative schemers who make it their business to watch the advancing wave of improvement, and gather its foam in the form of patented monopolies, which enable them to lay a heavy tax upon the industry of the country, without contributing anything to the real advancement of the arts. It embarrasses the honest pursuit of business with fears and apprehensions of concealed liens and unknown liabilities to lawsuits and vexatious accountings for profits made in good faith.” Atlantic Works v. Brady, 107 U.S. 192, 200, 2 S.Ct. 225, 231, 27 L.Ed. 438; see also Railroad Supply Co. v. Elyria Iron & Steel Co., 244 U.S. 285, 293, 37 S.Ct. 502, 61 L.Ed. 1136. Claim 10 of ’775 This claim is invalid also because of its failure to meet the requirements of R.S. § 4888, 35 U.S.C.A. § 33. The statute requires the inventor to define his invention “in such full, clear, concise, and exact terms as to enable any person skilled in the art or science to which it appertains, * * * to make, construct, compound, and use the same,” and, to “particularly point out and distinctly claim the part, improvement, or combination which he claims as his invention or discovery" (Emphasis by the Court.) This claim is invalid particularly because of its failure to satisfy the latter requirement. The invention of claim 10 is therein defined as follows : “A method of sizing paper making fibres which consists in treating the fibres with a solution of sulphate of alumina in such a manner that when a size is added to the paper stock chest, the size will react •with the fibres more rapidly than it will with the solution. (Emphasis by the Court.) This disclosure, construed in the light of the specifications of the patent, may be sufficiently instructive to enable persons skilled in the art to practice the method therein described, but, even when so construed, it fails to define “the limits of the monopoly asserted” with the required certainty. “Patents, whether basic or for improvements, must comply accurately and precisely with the statutory requirements as to claims of invention or discovery. The limits of a patent must be known for the protection of the patentee, the encouragement of the inventive genius of others, and the assurance that the subject of the patent will be dedicated ultimately to the public. The statute seeks to guard against unreasonable advantages to the patentee and disadvantages to others arising from uncertainty as to their rights. The inventor must ‘inform the public during the life of the patent of the limits of the monopoly asserted, so that it may be known which features may be safely used or manufactured without a license and which may not.’ The' claims ‘measure the invention.’ * * * In a limited field the variant must be clearly defined.” General Electric Co. v. Wabash Appliance Corporation, 304 U.S. 364, 369, 58 S.Ct. 899, 901, 82 L.Ed. 1402. “The statutory requirement of particularity and distinctness in claims is met only when they clearly distinguish what is claimed from what went before in the art and clearly circumscribe what is foreclosed from future enterprise. A zone of uncertainty which enterprise and experimentation may enter only at the risk of infringement claims would discourage invention only a little less than unequivocal foreclosure of the field. Moreover, the claims must be reasonably clear-cut to enable courts to determine whether novelty and invention are genuine. Congress has provided that a patent may be awarded only for a new and useful manufacture ‘not patented or described in any printed publication in this or any foreign country, before his invention or discovery thereof.’ ” United Carbon Co. v. Binney Co., 317 U.S. 228, 236, 63 S.Ct. 165, 170, 87 L.Ed. 232. Strict adherence to the requirements of the statute should be demanded where, as here, the disclosure of the patent is but one of many similar disclosures in a crowded art. It should be noted that at the conclusion of the trial the plaintiff, over the objection of the defendant, attempted to voluntarily withdraw claim 10 from suit. This may not be done under the circumstances existing in this case. The defendant, having filed a counterclaim invoking the determination of the issue of validity, is entitled to insist upon an adjudication. Altvater v. Freeman, 319 U.S. 359, 63 S.Ct. 1115, 87 L.Ed. 1450. Infringement An assumption of validity, for the purpose of passing on the question of infringement, must be predicated upon a narrow construction of the patent. The respective claims of the patent, construed in the light of its specifications and the disclosures of the prior art, must be limited to the specific combination of expedients therein defined, to wit, first, “treating the paper making fibres with sulphate of alumina, allowing the fibres to absorb the alum” (sulphate of alumina) “until the pH of the solution is over 5”; and, second, “then treating the surface of the astringent fibres with a solution of rosin size.” Royer v. Coupe, 146 U.S. 524, 13 S.Ct. 166, 36 L.Ed. 1073. Any other construction would bring the claims into conflict with the specifications and extend them beyond the necessarily narrow bounds of the patent. The invention, as thus defined in the claims, comprises two integral elements : The successive steps of the method, as distinguished from the chemical process, and, the operative principle of the chemical process. The failure to substantially follow this combination of elements, and in the manner prescribed in the patent, negatives infringement. Royer v. Coupe, supra; United States Glass Co. v. Atlas Glass Co., 3 Cir., 90 F. 724; Jensen-Salsbery Lab. v. O. M. Franklin Blackleg Serum Co., 10 Cir., 72 F.2d 15; Winget Kickernick Co. v. Sil-O-Ette Underwear Corporation, 2 Cir., 89 F.2d 635, certiorari denied, 302 U.S. 723, 58 S.Ct. 44, 82 L.Ed. 559; John Waldron Corporation v. Equitable Paper Bag Co., 3 Cir., 106 F.2d 724; Texas Co. v. Anderson-Prichard Refining Corporation, 10 Cir., 122 F.2d 829; United States Rubber Co. v. General Tire & Rubber Co., 6 Cir., 128 F.2d 104; Universal Oil Products Co. v. Globe Oil & Refining Co., 7 Cir., 137 F.2d 3, affirmed 322 U.S. 471, 64 S.Ct. 1110, 88 L.Ed. 1399. We must here determine which elements of the invention, if any, are employed in the accused process, and, if so employed, in what manner. The elements of the accused process must be separately examined and compared with the elements of the invention. The very essence of the invention, aside from the operative principle of the chemical process embodied therein, resides in the sequence of steps: the introduction into the stock of sufficient aluminum sulphate to coagulate the size, followed by the introduction of the rosin size emulsion. The claims, construed in the light of the specifications, define only this sequence. The accused process embraces three successive steps: first, the introduction into the stock of sufficient aluminum sulphate to overcome the cwbonates present in the water; second, „the introduction into the stock of the rosin size emulsion; and, third, the introduction into the stock of sufficient aluminum sulphate to coagulate the size. This succession of steps, upon a cursory examination, would appear to constitute an encroachment upon the sequence of steps embodied in the invention, but this is not the fact. The successive steps of the accused' process, and in the combination and sequence employed by the defendant, are embodied in the common practice of the prior art. The sizing process employed by the defendant consists of but two steps, the second and the third. We repeat them to emphasize the distinction: the introduction into the stock of the rosin size emulsion, follovacd by the introduction into the stock of sufficient aluminum sulphate to coagulate the size. This is a reversal of the sequence of steps defined in the claims. It cannot be seriously contended that this reversal of steps is employed as a subterfuge to avoid the charge of infringement because it clearly violates the specific teaching of the patent. The second element of the invention, the operative principle of maintaining the degree of acidity in the stock, within predetermined limits, is utilized by the defendant in the accused process. The range of acidity employed by the defendant in each of its operations substantially coincides with those disclosed -by the cited references of the prior art. Machine One It appears from the plaintiffs proof that the degree of acidity in the stock during the sizing reaction is maintained within the predetermined range of 5.2 pH and 5.5 pH. It is our opinion, based upon the testimony, that this range is not accurate. The degree of acidity in the stock is within the approximate range of 4.5 pH and 5.5 pH; the maximum of acidity is produced immediately upon the introduction of the aluminum sulphate into the stock as it leaves the jordan chest. The plaintiff’s proof clearly ignores the degree of acidity at this stage of the defendant’s operation. The difference, however, is not material. Machine Two It appears from the plaintiff’s proof that the degree of acidity in the stock during the sizing reaction is maintained within the predetermined range of 4.7 pH to 5.2 pH. It is our opinion, based upon the testimony, that this range is not accurate. The degree of acidity in the stock is within the approximate range of 4.4 pH and 5.2 pH; the maximum of acidity is produced immediately upon the introduction of the aluminum sulphate into the stock as it leaves the jordan chest. The plaintiff’s proof clearly ignores the degree of acidity at this stage of the plaintiff’-s operation. The difference, however, is not material. Machine Three The range of acidity maintained in each of the operations carried out on Machine Three coincides with the respective ranges maintained on Machines One and Two. It is evident that the optimum of acidity maintained by the defendant in its practice of the accused process, although not entirely within the range defined in the patent in suit, encroaches upon that range. It is equally evident, however, that this optimum of acidity substant