DISPENSATORY OF THE U. S. OF AMERICA. 179 
the English chemical manufacturers presented. In this is 
exhibited the advantage and facility of applying the useless 
products of one manufactory to the purposes of another; the 
materials from which it is fabricated being gas liquor and 
bone spirit — the first afforded by gas works, the latter by 
ivory-black establishments. 
Magnesias carbonas. — " Two kinds of Carbonate of Mag- 
nesia are distinguished; the light and the heavy. The light 
carbonate is the kind manufactured in Scotland. The heavy, 
according to Dr. Pereira, may be manufactured as follows: 
Add one volume of a cold saturated solution of carbonate of 
soda to a boiling mixture of one volume of a saturated solu- 
tion of sulphate of magnesia, and three volumes of water. 
Boil until effervescence has ceased, constantly stirring with 
a spatula. Then dilute with boiling water; set aside; pour 
off the supernatent liquor, and wash the precipitate with hot 
water on a linen cloth; afterwards dry it by heat in an iron 
pot." 
In the part devoted to preparations, which constitutes the 
second portion of the work, much new matter has been intro- 
duced, and such alterations made as have been rendered ne- 
cessary by the advance in our pharmaceutic knowledge. 
Under the head of Acetic Acid, is given a more detailed 
account of the mode of production and comparative strength 
of the different officinal products; and the specific gravities 
are presented in a tabular form. Hydrocyanic acid, Oil of 
wine, Nitrous ether, Sweet spirit of nitre, as well as many 
others, are more satisfactorily treated of. Several new me- 
dicines have been introduced into the appendix, as belong- 
ing to the non-officinal list. The 'article upon displacement 
has been extended, and such specifications made of the me- 
thod as to render it available in pharmaceutic operations. 
We must forbear, however, from entering into further par- 
ticulars, and terminate a notice which has extended much 
beyond the limits contemplated when it was commenced. 
If the good that has been effected by the United Stated Dis- 
