86 U.S. 287 (1874), Mitchell v. Tilghman
|Citation:||86 U.S. 287, 22 L.Ed. 125|
|Party Name:||MITCHELL v. TILGHMAN.|
|Case Date:||March 04, 1874|
|Court:||United States Supreme Court|
APPEALS from the Circuit Court for the Southern District of New York, in which court R. A. Tilghman filed two bills in equity against R. G. Mitchell, under a patent granted to him the said Tilghman, for a process for making fat-acid and glycerin from natural fat; one bill having been filed during the first term of the patent, and the other under the extended term of the same patent.
In both cases final decrees were given in favor of Tilghman; and the defendant, Mitchell, took these appeals.
The bill set forth the grant of letters-patent to Tilghman,
October 3d, 1854, for fourteen years from January 9th, 1854, the reduction of the patented inprovement to use, and the infringment by Mitchell.
The invention claimed by Tilghman may be stated, in general terms, to be based upon the discovery that if water be heated to a high degree, and at the same time retained in a close vessel so that it cannot pass into the state of steam, but must remain in the liquid state, it will, while in such highly heated liquid state, possess a peculiar property of separating natural fat into its chemical constitutents, glycerin and fat-acids. He undertook to claim the employment of water in the liquid state, heated and under the pressure necessary to retain it in the liquid state as the decomposing agent. He asserted that prior to his discovery and invention, no one had ever known, used, or described the employment of highly heated water retained in the liquid state by pressure as such decomposing agent, and that under the law if he set forth this newly discovered decomposing power of liquid water heated and under pressure, and exhibited in his specification one mode of practically applying it, he was entitled to the exclusive use of this decomposing agent in treating facts for the purpose of separating them into fat-acids and glycerin.
To understand the questions at issue in this case, and passed upon by the court, there is first to be considered the phenomenon of heating water, &c., its behavior and properties when heated.
Water when heated in an open vessel at the surface of the earth passes into a state of vapor, at a temperature of 212º of Fahrenheit's thermometer; the waters expanding over eighteen hundred times in passing into steam. It is impossible to retain water in a liquid state, in an open vessel, after it has reached that temperature. If the vessel in which the water is heated, however, be overed, and the cover be fastened down, the water can be heated to any temperature whatever, and will still remain in the liquid state. The tendency of the water to pass into vapor increases with the
degree of heat applied to it, and there must, therefore, be a proportionate pressure or restraint by the inclosing vessel on the heated water to overcome this expansive tendency, or tendency to pass into a state of a vapor.
Vessels in which water could be heated to any desired temperature, and the water still retained in the liquid state, were known in the arts, and called 'digesters.'
To understand matters further a brief statement of the art of treating fat is necessary.
Fats obtained from various sources differed much in hardness and fusibility, and each variety was formerly supposed to be an entirely different article. About 1816, Braconnot, a French chemist, discovered that all natural fats were merely mechanical mixtures, in various proportions of fats entirely solid and hard, now called stearin, with a more fluid fat or oil, called olein. He found that simple pressure very slowly applied, squeezed out the more fluid part, and that the remainder made harder candles. But the process of separation by pressure was difficult and imperfect.
Chevreul, in 1825, discovered that all fats were chemical compounds of a substance called glycerin, with fatty bodies having slight acid characters called fatty acids; that fatty acids were of different degrees of fusibility, and that when the glycerin was separated from fats, the fatty acids could be more rapidly and perfectly pressed so as to get out the hardest fatty acids for candles; and he patented a chemical process of separating these fatty acids from glycerin.
His process consisted of two distinct stages:
1. The manufacture of natural fat into soap, by boiling lime or other alkali with the fat, in which case fourteen pounds of lime were used to one hundred pounds of fat.
2. The decomposition of the soap so produced into fat-acid by the use of two pounds of sulphuric acid to each pound of lime.
Soap had always previously been made by boiling the fat and solution of alkali together, and Chevreul suggested that this production of soap could be expedited by boiling the
fat and the solution of alkali together under pressure. He did not, however, suggest that water alone, heated and under pressure, would of itself decompose neutral fat into a fat-acid and glycerin, but expressly mentioned alkali and sulphuric acid as the decomposing agents.
Another mode of separating free fat-acids was devised, which was calleddecomposition by sulphuric acid distillation.
This process was invented and used for producing fat-acid only, and not glycerin; the glycerin being destroyed by the process. It was asserted by Tilghman that this process differed from his:
1. In that the result produced was different, viz., fat-acid only, while his, Tilghman's, produced simultaneously both fat-acid and glycerin;
2. In that it required sulphuric acid to decompose the fat into fat-acid;
3. In that it did not depend for its efficiency on the use of highly heated water in the liquid state, retained in such state by pressure;
4. In that it was a process of distillation.
We must view here also the attempted decomposition by steam.
It was from time to time attempted, prior to Tilghman's alleged invention, to decompose neutral fat into fat-acid by distillation in a current of steam, but it was asserted by Tilghman that it was an unsuccessful and abandoned experiment, and had never come into use; and that even if it had been successful it differed in every way from his process. Among other ways,
In not producing glycerin as a result;
In not depending upon, or even allowing of, the presence of highly heatedwater under pressure;
In that it was a process depending on vaporization and subsequent condensation of the fat-acids;
In that the apparatus absolutely necessary for the distillation process was such as to render the execution of the hot-water process of him, Tilghman, in the same utterly impossible.
Tilghman asserted that he had made the discovery--not
that heat alone would decompose fats into fat-acid and glycerin, nor that the presence of water was necessary whem chemicals are used to decompose fats into fat-acid and glycerin--but merely that water in a liquid state, heated to a high degree of temperature while inclosed in a strong vessel, so as to prevent its passing into steam, would of itself and without the aid of chemicals separate natural fat into its constitutent elements, fat-acids and glycerin. Having made, as he alleged, this discovery of a new chemical decomposing property of water highly heated and retained in the liquid state by pressure, Tilghman, in his patent, announced it, and, as will be seen directly, also described two modes of carrying out his process based thereon.
In the alkaline saponification processes, which were in use prior to Tilghman's invention, various forms of closed boilers, provided with safety valves, were known. It was also known that fat and water would tend to remain unmixed in a boiler, and therefore agitators or circulators, for preserving a mixture or intimate contact between the fat and lime and water during the process of alkaline saponification, under pressure, were also in use. 1
The specification, in the patent, ran thus:
'Be it known that I, Richard Albert Tilghman, of Philadelphia, have invented a new and improved mode of treating fatty and oily bodies, and I hereby declare that the following is a full and exact description thereof.
'My invention consists of a process for producing free fat-acids and solution of glycerin from those fatty and oil bodies of animal and vegetable origin which contain glycerin as their base. For this purpose, I subject these fatty or oily bodies to the
action of water at a high temperature and pressure, so as to cause the elements of those bodies to combine with water, and thereby obtain at the same time free fat-acids and solution of glycerin. I mix the fatty body to be operated upon with from a third to a half of its bulk of water.
'And the mixture may be placed in any convenient vessel in which it can be heated to the melting-point of lead, until the operation is complete. The vessel must be closed and of great strength, so that the requisite amount of pressure may be applied to prevent the conversion of the water into steam.
'The process may be performed more rapidly and also continuously by causing the mixture of fatty matter and water to pass through a tube or continuous channel, heated to the temperature already mentioned; the requisite pressure for preventing the conversion of water into steam being applied during the process, and this, I believe, is the best mode of carrying my invention into effect.
'In the drawing hereunto annexed are shown figures of AN apparatus for performing this process speedily and continuously, but which apparatus I do not intend to claim as any part of my invention.
'Figure 1 of the said drawing is a...
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