other materials, is at present either converted in its original state into particles, which are thereupon gelatinized on the surface, or it is at the onset thoroughly gelatinized, and subsequently divided by mechanical means into small pieces or laminæ. In the first case the powder is not sufficiently resistant against the influence of damp air, while in the second case it is impossible to obtain grains of like size and form, which is so much the more prejudicial, as this nonuniformity is an obstacle to the complete expulsion of the solvents employed in the gelatinizing process, in consequence whereof a difference in the chemical constitution and explosive power of the grains results. For the purpose of obviating these defects I proceed as follows:

"The nitro-cellulose, or compound thereof with other substances, is first mixed with a liquid adapted to dissolve the former-such as ethyl-ether, methyl-ether, a solution of camphor in ether, a mixture of ether and alcohol, dinitro-toluol, etc.-and the mixture is kneaded or rolled until it has become plastic and the nitro-cellulose completely dissolved. To the mass thus obtained I introduce a liquid or vapor incapable of dissolving or otherwise acting chemically either on the nitro-cellulose or on the ingredients of the said compound thereof. Preferably I employ water or steam, or both together. At the same time the mass is stirred. By these means the mass is caused to split up into particles or grains, which become smaller in the measure as the stirring is continued and the temperature is raised. The grains are heated together with the same or any other like liquid, vapor, or steam unadapted to act chemically thereon, the temperature being carried to a degree somewhat above the boiling point of the solvent employed in order to completely drive out the latter. The said solvents are thereby extracted from the grains and evaporated; but they may be recovered by distillation. Thereupon the grains are separated from the liquid or withdrawn from the steam or vapor and dried, and finally they are treated in the ordinary manner in view of producing finished gun or blasting powder.

"The described method of extracting the solvents may also be applied to grains composed of or containing gelatinized nitro-cellulose, which are produced by means different from those specified.

"I claim as my invention:

"(1) The process of gelatinizing and granulating nitro-cellulose or a compound thereof with other substances, which consists in adding to the said nitro-cellulose or compound a solvent of the former, kneading the mass until the same has become plastic and the nitro-cellulose thoroughly gelatinized, introducing thereto a liquid or vapor chemically indifferent to the constituents of the mass, and stirring the latter until complete granulation has been produced, substantially as described.

"(2) The process of treating grains composed of gelatinized nitro-cellulose or of a compound thereof with other substances and still containing the solvent employed for the purpose of gelatinization, the said process consisting in exposing the grains to a heated liquid or vapor chemically indifferent to the solid constituents thereof and afterward drying the grains, substantially as described.

"In testimony whereof I have hereunto set my hand in the presence of two subscribing witnesses. Richard Von Freeden,

"Witnesses:

"W. H. Edwards.
"W. Haupt."

The nitro-cellulose here referred to, is an explosive nitrate of cellulose, commonly known as "gun cotton." It is made by digesting clean cotton in a mixture of nitric and sulphuric acid. There are other nitrates of cellulose made with weak acids and a short period of digestion, which are not gun cotton, or the particular nitrate with which we are here concerned. This nitro-cellulose, or gun cotton, is soluble in certain liquids, as stated in the specifications of the patent, such as ethyl-ether, methyl-ether, a solution of camphor in ether, etc. When one of these solvents is mixed in proper proportion with wet

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gun cotton, and the mixture kneaded or rolled for a sufficient length of time, the cellulose fibre is wholly dissolved, and a homogeneous gelatinous mass is produced. The production of such a gelatinous mass, by the admixture and kneading of the solvent with the gun cotton, was well known in the art at the date of the patent, and forms the raw material, so to speak, of the process of the patent. Indeed, the Pfleiderer kneading machine, used by the complainants for working together the solvent and the gun cotton into a gelatinous mass, was one already devised by the person whose name it bears, and probably superseded some other mode of kneading in use prior to the patent in suit. It is only important to bear in mind, that a "gelatinous and plastic" mass, produced by this or a similar kneading or rolling process, in which the nitro-cellulose has become "completely dissolved," is the absolutely necessary starting point for the process described in the specifications and first claim of the patent in suit.

Starting, then, with this plastic mass, so produced and described, "my invention," says the patentee, "is based on the discovery made by me that gelatinized nitro-cellulose still containing the solvent employed for its gelatinization on being exposed to certain liquids or to vapors thereof undergoes a kind of coagulation and a division into small lumps, which latter is promoted by stirring." The invention or discovery of the patent is clearly stated to be the division of this gelatinized mass into lumps, by the exposure thereof to certain liquids or vapors chemically indifferent thereto, and that this result is promoted by stirring. It is a process of granulation, and involves the formation of a plastic mass, by kneading a mixture of nitrocellulose and its solvent, so that the nitro-cellulose is "completely dissolved." The method of forming this plastic mass is precisely what it was in the art prior to the patent. It is accomplished without the use of water, and constitutes the first step of the process.

The specification of the patent says:

"To the mass thus obtained I introduce a liquid or vapor incapable of dissolving or otherwise acting chemically either on the nitro-cellulose or on the ingredients of the said compound thereof. Preferably I employ water or steam, or both together. At the same time the mass is stirred."

This is the second step in the process; and that there is here described whatever there is of invention, as covered by the first claim of the patent, is apparent from the language of the specification which immediately follows:

"By these means [that is, by the introduction of the water or steam, and the stirring] the mass is caused to split up into particles or grains, which become smaller in the measure as the stirring is continued and the temperature is raised."

The process, therefore, is one of granulation of a previously formed gelatinized and plastic mass, in which the gun cotton has been completely dissolved, and which still contains the solvent.

The description of the process in the specifications would seem to assume that the water or steam is introduced to the plastic mass in the same vessel in which it was being kneaded for the purpose of gelatinization, and that the stirring required after the introduction of the

water or steam, is a continuation of the same kneading process in the same vessel and by the same kneading blades or paddles. It is this process of granulation which the patentee describes as his contribution to the art. Prior thereto, the state of the art is thus described in the

letters patent:

"In view of producing such gunpowder, which is not affected by moisture, the nitro-cellulose, whether pure or mixed with other materials, is at present either converted in its original state into particles which are thereupon gelatinized on the surface, or it is at the onset thoroughly gelatinized and subsequently divided by mechanical means into small pieces or laminæ."

Neither of these methods, says the patentee, were entirely satisfactory, as, in the first case, the powder was not sufficiently resistant to moisture, and in the second, it was impossible to obtain grains of like size and form. The method in the prior art nearest to that in the patent in suit, was the last described. It could have been practiced by gelatinizing, as already described, pulped wet gun cotton, by mixing it with a solvent and thoroughly kneading it in one of the Pfleiderer kneading machines, used in forming the gelatinized plastic mass of the patent in suit. Up to this point the processes are the same. The old method, however, was to take this gelatinized plastic mass, and, having rolled it into thin sheets, mechanically cut it into small flakes or pieces. Von Freeden takes the same mass and introduces thereto water or steam, the mass still being stirred or kneaded, and says that he finds that it will break up into grains. That is, Von Freeden broke up or granulated his gelatinized mass (presumably) in the kneading machine, by introducing thereto water or vapor, while it was still being kneaded or stirred, instead of mechanically cutting the same into flakelike grains, when rolled into sheets. Von Freeden claims to have devised a new means, to take the place of the old mechanical means, of dividing into grains the mass of completely dissolved nitro-cellulose. This is the process described in the first claim, which we again quote:

"I claim as my invention:

"(1) The process of gelatinizing and granulating nitro-cellulose or a compound thereof with other substances, which consists in adding to the said nitro-cellulose or compound a solvent of the former, kneading the mass until the same has become plastic and the nitro-cellulose thoroughly gelatinized, introducing thereto a liquid or vapor chemically indifferent to the constituents of the mass, and stirring the latter until complete granulation has been produced, substantially as described."

The second claim of the patent refers to the mode of treating the grains after they are formed, by heat, so as to drive off the solvent, before drying the grains and sorting them for use. This claim will be considered separately.

The defendant's process is alleged to infringe that of the complainants, as covered by the first claim of the patent in suit, and the specifications relating thereto, and we must now examine it in the light of the testimony and exhibits in the case.

Mr. Francis G. Du Pont, then vice president of the defendant company, who was called as a witness by the complainants at the beginning of the taking of testimony, described the process by which the defendant carried on the manufacture of smokeless powder prior to the filing

of the bill of complaint, and subsequent to the grant of the patent in suit to Von Freeden, June 3, 1890. His description is substantially as follows:

"In carrying on the process there is used a stationary vertical cylindrically formed still of substantially the form and construction of the still marked 'A' in the drawings attached to letters patent No. 503,586 granted to Francis G. Du Pont on August 22, 1893. Around the outside of the lower portion of the still is a jacket in which steam may be caused to circulate when it is desired to heat the contents of the still. A rotatable shaft [not shown in the drawing] extends downward through a stuffing box in the top of the still to a point near its bottom and carries six arms extending across it, each arm attached at its central point to the shaft and at points on the shaft about eight inches apart, and the ends of the arms reach nearly to the wall of the still."

Drawing Accompanying Du Pont Patent No. 503,586.

A large quantity of water, stated by Mr. Francis I. Du Pont (son of Francis G. Du Pont), on a rough estimate, to amount to about 21⁄2 to 3 tons, in which about 5 per cent. of barium nitrate and 2 per cent. of saltpeter have been dissolved, is then pumped into the still, only partially filling the same. At the time of the introduction of the water, the horizontal stirrers are set in rotation and continued so during the whole of the process. Finely pulped wet gun cotton, sometimes amounting, according to Mr. F. I. Du Pont, to as much as 450 or 500 pounds, and which has not as yet been subjected to the action of any solvent, is then thrown into the still through an opening in its upper part, and by the action of the stirrer blades then going on, is immediately mixed through the water in the still, forming a whitish liquid of about the consistency of milk. "More water, in which barium nitrate and saltpeter have been dissolved, is then pumped into the still, until the surface of the liquid in the still is about on a level with the upper stirrer blades on the vertical shaft." The stirrer blades are rotated at a speed sufficient to maintain the particles of gun cotton in mechanical suspension in the water. An emulsion, formed by beating up amyl acetate, which is a solvent of nitro-cellulose, in water in which barium nitrate and saltpeter have been dissolved, is then pumped into the still. The volatile, oily particles or globules of the solvent at once seize upon the finely divided particles of nitro-cellulose suspended in the liquid in the still, the constant stirring serving to distribute the particles of emulsion thoroughly throughout the liquid and to bring them into contact with the fine particles of nitro-cellulose, partially gelatinizing and granulating the same. This gelatinization and granulation is practically instantaneous, as both are simultaneously effected within 5 minutes after the introduction of the emulsion into the still is begun, and it is in testimony that it takes several minutes for the whole emulsion to be run into the still (whereas, according to the testimony of Mr. Hesse, managing agent of complainants, and produced as a witness by them, the kneading of the mixture of gun cotton and its solvent into a gelatinous and plastic mass takes 30 minutes, and the disintegration of the same into grains, before the evaporation of the solvent begins, takes 15 minutes more).

The description so far relates to the granulation of the materials. introduced into the still, to wit, the finely divided, pulpy nitro-cellulose, held in suspension throughout the liquid in the still, and the solvent emulsion afterwards introduced; and, as already observed, such granulation is practically instantaneous upon the meeting of the globules of the emulsion and the fine particles of nitro-cellulose, held in suspension throughout the liquid. The process up to this point is clearly not, as in that of Von Freeden, the disintegration and breaking up of a previously formed gelatinized mass of nitro-cellulose, in which the fiber has been thoroughly dissolved (the said breaking up of the mass, presumably, from the specifications and claims of the patent, taking place in the kneading machine while being kneaded and torn by the blades of the machine, and softened by exposure to water or steam), but is a building up of grains by the meeting and union of small particles of the finely divided nitro-cellulose, as suspended in the liquid in the still, with the small globules or particles of the solvent; these con