CARBONATES. 383 



If crystallized, 2 proportions of water, 18, will make the equivalent, 

 94. 



The trona of Africa is said to be a sesqui-carbonate,* that is, in- 

 termediate between the carbonate and bi-carbonate, consisting of 

 Carbonic acid, 39.76 or 3 proportions =66 

 Soda, - - 38.55 or 2 " 64 



Water, - - 21.69 or 4 " 36 



100. 166 its equivalent. 



3. USES. An elegant antacid; it is now prepared in the large 

 way, and is perhaps preferable, on some accounts, to the bi-carbon- 

 ate of potassa. It is taken freely ; the dose mentioned in the phar- 

 macopoeias is two scruples a day, using the effloresced crystals, which 

 will contain about twice as much alkali as the crystals. It may be 

 taken in powder or in pills. It should be kept in families. 



The effervescing draughts which are made with what are called 

 soda powders are not soda water ; the powders are put up in papers ; 

 the blue paper contains half a drachm of carbonate of soda, and the 

 white twenty five grains of tartaric acid, which require half a pint of 

 water ; the effervescing drink is a mixture of tartrate of soda and car- 

 bonic acid, with perhaps some free alkali. The Seidlitz powders 

 have two drachms of tartarized soda and two scruples of carbonate 

 of soda in the white paper, and thirty five grains of tartaric acid in 

 the blue ; to a solution of the former in half a pint of water the latter is 

 added. These preparations are however both useful and agreeable. f 



CARBONATES OF AMMONIA. 



1. NAMES, &c. In the shops, volatile salts or concrete, volatile 

 alkali, sal cornu cervi, or salt of hartshorn ; volatile salts, is the name 

 most familiar to the apothecary, (it is now called in chemistry, sesqui- 

 carbonate.) 



2. PREPARATION, of the salt of the shops. 



(a.) Obtained in the manufactories, by distilling, in earthen or iron 

 retorts bones, horns, or other firm animal substances."^ 



(b.) In pharmacy, by heating dry chalk, 1 part, and dry muriate 

 of ammonia, 2 parts, in an earthen retort, or one of coated glass ; 

 the sublimed salt is condensed in a cold receiver. 



(c.) Process of the apothecaries. Muriate of ammonia, 1 part, 

 and carbonate of lime, l, are mingled, 100 cwt. or more at once; 



* See Quart. Jour. VII. 298, and Henry, Vol. I, p. 566, 10th ed. 



t Coxe. t See Ammonia, p. 236. 10. 



It will be seen, farther on, that the salt formed in this manner has different pro- 

 portions from that which is prepared by mingling the gases in equal volumes ; the 

 latter is strictly the carbonate. ^ 



