I begin this analysis with an examination of the milk of animals that feed wholly on vegetables; because, though this substance be elaborated in the body of the animal, and by that means brought nearer to the nature of animal matters, yet it still retains a great similitude to the vegetables from which it derives its origin, and is a sort of intermediate substance between the vegetable and animal. Then I proceed to the analysis of animal matters properly so called, those which actually make a part of the animal body. I next examine the excrementitious substances, that are thrown out of the animal body as superfluous and useless. And then I conclude this latter part with operations on the Volatile Alkali; a saline substance of principal consideration in the decomposition of animal matters. Though, in the general view here given of the order observed in this Treatise of Practical Chymistry, I have mentioned only such processes as serve for analysing bodies, yet I have also inserted some other operations of different kinds. The book would be very defective if it contained no more: for the design of Chymistry is not only to analyse the mixts produced by nature, in order to obtain the simplest substances of which they are composed, but moreover to discover by sundry experiments the properties of those elementary principles, and to recombine them in various manners, either with each other, or with different bodies, so as to reproduce the original mixts with all their properties, or even form new compounds which never existed in nature. In this book therefore the reader will find processes for combining and recompounding, as well as for resolving and decomposing bodies. I have placed them next to the processes for decomposition, taking all possible care not to interrupt their order, or break the connection between them. PART I. OF MINERALS. SECTION I. _Operations performed on Saline Mineral Substances._ CHAP. I. _Of the_ VITRIOLIC ACID. PROCESS I. _To extract Vitriol from the Pyrites._ Take any quantity you please of Iron Pyrites; leave them for some time exposed to the air: they will crack, split, lose their brightness, and fall into powder. Put this powder into a glass cucurbit, and pour upon it twice its weight of hot water; stir the whole with a stick, and the liquor will grow turbid. Pour it, while it is yet warm, into a glass funnel lined with brown filtering paper; and having placed your funnel over another glass cucurbit, let the liquor drain into it. Pour more hot water on the powdered Pyrites, filter as before, and so go on, every time lessening the quantity of water, till that which comes off the Pyrites appears to have no astringent vitriolic taste.