Experiments and Observations on the Following Subjects / 1. On the preparation, calcination, and medicinal uses of Magnesia Alba. 2. On the solvent qualities of calcined Magnesia. 3. On the variety in the solvent powers of quick-lime, when used in different quantities. 4. On various absorbents, as promoting or retarding putrefaction. 5. On the comparative antiseptic powers of vegetable infusions prepared with lime, &c. 6. On the sweetening properties of fixed air. - Thomas Henry

ERRATA.

Page 8, line 14, after quantity read of water.
Page 10, line 18, for interrupt read intercept.
Page 13, line 1, read is there said.
Page 16, line 1, read the other absorbents.
Page 29, note, line 4 from the bottom, for albuminis read aluminis.
Page 31, line 4, for patients read parents.
Page 83, line 9, after elegant read green.
Page 126, line 3, erase the comma after smell.
Page 127, line 3, place a comma instead of the semicolon.

CHAP. I.

An account of an improved method of preparing MAGNESIA ALBA.

ALTHOUGH Magnesia Alba is a medicine which has been in general use for many years, yet the proper mode of making it is very little known. Our pharmacopæia affords us no information about it; and the formula which is given by the Edinburgh College, as well as that with which the ingenious Doctor Black [b] has favoured us, is deficient in several circumstances. Hence the preparation of pure Magnesia has been confined to very few persons, who have preferred the emolument they have received by keeping their method secret, to the more diffusive utility of which a publication of it would have been productive.[c] I therefore beg leave to lay before the public a process for the preparation of Magnesia, by which it will be in the power of every Apothecary to make it himself, in all respects equal to that which is sold by those who conceal their method.

I am the more strongly induced to make this communication, because the Magnesia which is generally to be found in the shops, is either extremely coarse and ill prepared, or, which is still worse, sophisticated with calcareous substances, differing greatly from true Magnesia. I have been assured by some Physicians, that they have met with it mixed with chalk, and even with lime, and I have sometimes seen it so adulterated: a fraud of very dangerous tendency, as this powder is so frequently administered to very young infants, and to adults of tender bowels and costive habits.

This medicine was originally prepared abroad, from the liquor called the mother of nitre, which is composed of a light earth united with an acid; and these being separated, either by a strong fire, or by the addition of an alkali, the powder was washed in water, and obtained the name of Magnesia Alba. Hoffman afterwards prepared it from the bittern remaining after the crystallization of sea salt, which he found to be similar to the mother of nitre. And the factitious Epsom salt being prepared from this bittern, and evidently composed of Magnesia and the vitriolic acid, Dr. Black, who has favoured the world with a number of very valuable experiments on this subject, made use of this salt with success for the same purpose.