392 CARBONATES. 



the carbonate of lime; soluble in 1536 parts of boiling water. It is 

 insipid. 



(b.) Fusible at 226, W. into a glass ; losing 5 or 6 per cent, of 

 its carbonic acid ; in a black lead crucible, and especially if mixed 

 with charcoal and oil, the carbonic acid is wholly expelled, and the 

 caustic earth remains ; this may be done in a smith's forge ; in a 

 strong fire, it fluxes a Hessian crucible and produces a glass resemb- 

 ling chrysolite. 



!c.) Air does not affect it. 

 d.) Decomposed by the acids, with effervescence. 



4. COMPOSITION. According to the analysis of Stromeyer,* the 

 artificial carbonate contains no water, and has very nearly .30 car- 

 bonic acid, and .70 strontia. 



The equivalent of strontia, is 52, that of carbonic acid, 22, and as 

 22 J 52 : : 70 : 30, very nearly ; so that the theoretical constitution 

 agrees almost with the results of analysis. 



5. MISCELLANEOUS. 



(a.) Strontia takes the carbonic acid from all the alkalies ; its car- 

 bonate, with the aid of heat, is decomposed by baryta only ;f still it 

 is uncertain which of the alkaline earths has the stronger attraction 

 for carbonic acid.J Distinguished from carbonate of baryta, by an 

 inferior sp. gr. by the fact that its salts yield their acids to baryta, 

 and that it is not poisonous ; animals may take it with impunity ; its 

 nitrate tinges the flame of a candle red ; that of baryta tinges it yel- 

 low; under the compound blowpipe, all its varieties give a red 

 flame, and all those of baryta a yellow one. It has never been intro- 

 duced into medicine, and is of no use except to chemists. 



CARBONATE OF MAGNESIA. 



1. HISTORY. Long known, but not well understood till Dr. 

 Black gave its true theory, as well as that of lime and the alkalies.^ 



2. PREPARATION. 



(a.) By slowly dissolving pure magnesia in liquid carbonic acid.\\ 



* Ann. de Chim. et de Phys. Ill, 396. 



t Four. IV, 22. t Dr. Hope. 



Every student should read Dr. Black's own account of the gradual developement 

 of this curious and instructive subject namely, the relation of carbonic acid to the 

 alkaline substances ; it is a fine example of inductive reasoning, and has contributed 

 more than any other thing to the progress of pneumatic chemistry. See Robison's 

 Black's Lectures. 



|| A native carbonate of magnesia has been found in the East Indies, and analyzed 

 by Dr. Henry, Ann. of Philos. N. S. I, 252. Native carbonates have been found at 

 Hoboken, near New York, Am. Jour. Vol. I. Calcined or pure magnesia, unlike 

 the alkalies and the other alkaline earths, does not absorb much carbonic acid from 

 the air, and consequently, it acquires little weight except from the absorption of wa- 

 ter, which makes it a hydrate, and it afterwards acquires some carbonic acid. 



