Page:Proceedings of the Royal Society of London Vol 1.djvu/304

Rh a man, he again made a dog the subject of experiment; and after he had tied the pylorus, about three ounces of a mixture of tincture of rhubarb with water were at intervals injected into his stomach. Upon killing this dog, at the expiration of eight hours and a half, his bladder was found distended with urine highly tinctnred with the rhubarb. The spleen was turgid; and, when cut through and examined by a magnifying—glass, appeared to consist of two parls intermixed, but very distinguishable from each other by their colour; the one was transparent, in the form of small circles or ovals, and surrounded by a different structure, which was vascular, of a red colour, but of a ﬁghter hue than the substance of the liver.

This spleen was immersed in water, and being cut into small pieces, the water became discernibly impregnated with the rhubarb, as was rendered manifest by the test of alkali.

On the contrary, an equal portion of the liver of the same dog. treated in the same way, gave no such colour to the water, but only tinged it with blood of a red colour. Although ﬂuids are thus found to pass from the stomach to the spleen, the vessels by which they are conveyed have not been detected, nor does Mr. Home entertain much hope of such a discovery.

Mr. Smithson gives a particular description of the form of the sulphuret of lead, antimony, and copper, because that which was laid before the Society in 1804 appeared to him materially inaccurate and imperfect; and he further offers some observations upon Mr. Hatchett’s experiments, which he deems essentially necessary to our rightly understanding this substance, as well as many other chemical compounds to which the same principles extend.

The author conceives it not to be probable that this ore is a direct quadruple combination of the three metals, lead, antimony, and copper, With sulphur; but thinks it much more credible that it consists of the three sulphurets of these metals.

On this presumption he makes experiments, to determine the proportion of these sulphurets to each other; and since 10 grains of galena produce 12½ sulphate of lead. he thence infers the quantity of galena indicated by 60.19 grains of sulphate of lead, obtained by Mr. Hatchett. So also with respect to sulphate of antimony:— as 10 grains yield 11 of precipitate from muriatic acid by water, he is enabled to determine the quantity of sulphuret of antimony, corresponding to Mr. Hatchett’s precipitate of 28.64 grains. With respect to sulphate of copper, his method is not so direct; for as he had none of this sulphuret on which to make experiments, he only presumes that the remainder of the ore consists of this compound; and hence he obtains the following results: sulphuret of lead, 49.7; sulphuret of antimony. 29‘6; sulphuret of copper, 207.

From the near agreement of these numbers with the simple pro-