“583. The only substance of the kind, perhaps, worth keeping in solution, is an acid infusion of red cabbage. For its preparation, one or more red cabbages should be cut into strips, and boiling water poured upon the pieces; a little dilute sulphuric acid is to be added, and the whole well stirred: it is then to be covered and kept hot as long as possible, or, if convenient, should be heated nearly to boiling, for an hour or two, in a copper or earthen vessel. The quantity of water to be added at first should be sufficient to cover the cabbage, and the sulphuric acid should be in the proportion of about half an ounce of strong oil of vitriol by measure to each good-sized plant. This being done, the fluid should be separated and drained off, and as much more hot water poured on as will cover the solid residue, adding a very little sulphuric acid. The whole is to be closed up, and suffered to stand until cold, and then the liquid poured off and added to the former infusion. The cabbage may now be thrown away. The infusion is to be evaporated to one half or one third its first bulk, poured into a jar, allowed to settle, and the clear red fluid decanted and preserved in bottles. The residue may have water added to it, the solid part be allowed to subside, the clear liquor drawn off, evaporated and added to the former, or it may be dismissed altogether. This solution will keep for a year. When [p279] required for use, the acid of a small portion of it should be neutralized by caustic potash, or soda, (not by ammonia,) when it will assume an intensely deep blue colour, and will, in most cases, require dilution with twelve or fourteen parts of water. The red liquor of pickle cabbage will, occasionally, answer the uses of the solution, and is, when required for service, to be neutralized in a similar manner.” For test-papers, litmus and turmeric are the most essential, and several precautions in preparing and using them are here pointed out, which, though apparently trivial, are, in fact, extremely important in insuring correct conclusions. We transcribe a part of the account of the applications of these coloured papers, as a specimen of the clear minuteness with which the details of the work are given, and as a sample of the author’s general method and style, where subjects of much greater intricacy are to be explained.