_On the Sweetening Properties of Fixed Air._ 114
_A Review of the general Conclusions deducible from the foregoing Observations and Experiments._ 135
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_.
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.
[b] Essays and Observations Physical and Literary, Vol. II.
[c] Mr. Glass, a few years since, published an Essay on Magnesia Alba, in which all the information he affords us relative to the preparation is what we knew before, viz. that it is prepared from Epsom salts and pot ashes; and has related a number of difficulties which occur in the process, at the same time carefully, I had almost said meanly, avoiding giving the least instruction which might teach us how to shun them, though he has given a long detail of the many tragical consequences which may attend the use of Magnesia prepared under such disadvantages.
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.