be drawn off, and about two gallons of fresh water to each ton of rough fat or stuff is to be then put in the rendering vat, and the steam let on again and continued till the tallow has boiled about ten minutes. After this washing process the boiling is to be stopped, and the materials left to settle, in order that the tallow may be come cool, and fit to be packed off.

In rendering fish oils in wooden vessels, that is boiling or melting, and partly refining and purifying, such as whale blubber, fish livers, and other parts containing fish oils, the following modification of the process is necessary:

The rendering mixture, in this case, should contain the following proportion of sulphuric and muriatic acids: viz. four pounds of the former diluted with two gallons of water, as described in the former part of this specification (respecting tallow), and six of the latter acid also diluted with two gallons of water. These diluted acids are to be mixed together after the diluted sulphuric acid has become cold; and to this compound is then to be added, and well stirred therewith, half a pound of bichromate of potassa, and a like quantity of oxalic acid. This compound is to be added to the boiling animal oils, at intervals of twenty or thirty minutes, in the proportion of two quarts at each time of adding to every ton of materials under operation, until all the fatty or oily substances (such as whale blubber, livers of fish, and other parts containing oil) are reduced or rendered. This will be shown on examining the mass under operation, and indicated by any parts containing oil floating beneath the surface of the fluid oil, and above the surface of the water; and thereby the operator will know if the process is to be stopped or continued.

After this operation is performed, the under liquid and chemicals may be drawn off, and about two pounds weight of powdered chalk or marble to each ton of raw material is to be thrown into the vat, and well stirred therewith, when the whole is to be boiled for ten or twenty minutes, in order that the chalk or marble may combine with and remove any acid adhering to the oil. The now rendered or purified oil, is then allowed to settle, when it might be removed for use.

In the further refining and purifying of tallow, if necessary, or thought desirable at the time, the fresh water is put into the vat, after the pumping or drawing off the under water and chemicals, the rendering being completed, there may be added to every ton of tallow a half pound of green oxide of chrome or bichromate of potassa, and boiled with the materials under operation for about ten or fifteen minutes, by turning on the steam, the colour, odour, and other properties of the tallow, will be much improved by the process.

In refining and purifying animal and vegetable oils generally, when in their fluid state, as articles of commerce, the following compounds are to be added to every ton of oil:-A quantity, say one quart, of the before-mentioned mixture of muriatic acid and oxide of chrome, or bichromate of potassa, the oil being stirred well at each time this compound is added; the operation or commixture to be continued, until all the offensive odour, colouring matter, or impurities, are removed. I then introduce about three gallons of water to every ton of oil, and from two to three pounds of powdered chalk or marble, to remove any acids adhering to the oils. The oil is then to be left quiet until all the chemicals and water have settled, and it

has become transparent, when it may be run off into barrels for use.

In the case of palm oil, it being ordinarily in a solid state, it must be raised by artificial heat to the temperature of about 120 deg. Fahrenheit's thermometer; and the refining mixture will require to contain in the proportion of about one pound and a half of green oxide of chrome or bishromate of potassa, and four pounds of muriatic acid, to each ton of rough material, instead of the former proportions; and when the colouring matters are removed, the same quantity of chalk or marble is to be added, as in the former case, and three or four gallons of water, and the whole raised to the temperature of about 150 deg., when the materials will become sufficiently fluid to allow all the chemicals to subside; and after the same have been sufficiently stirred together, the whole may be kept at rest a sufficient time to allow the oil to become clear, and the chemicals to subside, when the oil may be used in various manufactures.

The Patentee concludes by saying, "Having now described my improvements and the manner of carrying the same into effect, and in such proportions and quantities as I have found to answer the purpose, I wish it to be under. stood that what I claim as my improvements in the preparing, purifying, and refining tallow, &c. is the boiling and operating upon them by the following compounds, chemical ingredients, or mixtures: viz. I claim the combination of sulphuric and nitric acids, and muriatic and nitric acids, for the purpose of rendering' in wooden vessels, and likewise oxalic acid, both singly and compounded, as described; and likewise the bichromate of potassa, as it much improves the tallow, and prevents the occasional temporary discoloration occasioned by nitric acid; I likewise claim the combi

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nation of nitric acid, with spirits of wine, naphtha, ether, or turpentine, as evolving nitrous gas and nitrous oxide for the purpose of rendering, and, by their agency, purifying and solidifying the tallow; I also claim the admixture of sulphuric and muriatic acids and oxalic acid, in rendering fish oils, as whale, seal, cod, &c.; I also claim the combination of muriatic acid with oxide of chrome, by which combination there results a double effect, viz. the bleaching or purifying, and refining effect of the bichromate of potassa or oxide of chrome, and the immense evolution of chlorine gas resulting from the decomposition of the muriatic acid or bichromate of potassa, for refining and bleaching vegetable and animal oils generally, and particularly as applied to palm oil, which I prefer operating upon at about the temperature of 120°, as that at which the effect is rendered most certain for success and steady operation.— [Inrolled in the Rolls Chapel Office, September, 1836.]

TO HUGH LEE PATTINSON, of Summer Hill-terrace, in the parish or parochial chapelry of St. John, in the county of Northumberland, agent, for his improved method of separating silver from lead.-[Sealed 28th October, 1833.]

In order to render the subject of this patent intelligible to the general reader, some introductory remarks should have been given as to the natural state of combination in which silver is sometimes found in the ore with lead; but the specification merely assumes the existence of the combina tion of a small quantity of silver in lead; and states, as is well known to metallurgists, that it is difficult to extract

Pattinson's, for Impts. in separating Silver from Lead. 299

the silver from the lead without destroying the latter by the operation; and that the entire sacrifice of the lead causes the expense to be so great, that the silver, when withdrawn, is found to have been more costly than valuable.

The improved method of proceeding proposed by the Patentee, arises from the discovery, that if lead, containing a small quantity of silver, is melted, and cooled slowly, that the pure lead will form in small particles like crystals on the top of the molten metal, and will, as it forms, gradually descend to the bottom, from whence it may be withdrawn by a strainer ladle, leaving the silver in the vessel with the fluid metal.

The mode of treating the compound metal, therefore, is to melt it, and suffer it to cool very gradually; then withdraw the small particles as they are formed, and submit these particles, as they are drawn out, to the heat of a reverberating furnace, by holding them in the strainer ladle within the furnace. This will cause some fluid metal to run out from the particles, which fluid is to be returned into the vessel it was first melted in, among the residuum of fluid metal.

By carrying on and repeating this process for some time, a great portion of pure lead will be withdrawn, and the silver left with the fluid metal in the melting pot, the lead having been reduced from its original quantity to about onethird; and this portion or residuum containing all the silver, may, with profit, be operated upon to obtain the silver in a pure state, while the other two-thirds of the metal being pure lead, having been preserved, may be melted for the purposes of commerce.-[Inrolled in the Inrolment Office, December, 1833.]