CARBONATES. 391 



4. COMPOSITION. Carbonic acid, "22, baryta, 78 = 100, its equiv- 

 alent. 



5. MISCELLANEOUS. Used for a long time in Lancashire, to kill 

 rats. With 40 grs. Mr. Watt killed a small dog 5 even 15 grains 

 will produce that effect. It appears that domestic fowls are some- 

 times killed by swallowing fragments of the native spar, and that 

 even cows, by licking it, suffer the same fate.* 



According to Dr. Hope, there is very little or no difference be- 

 tween lime and baryta in their attraction for carbonic acid ; lime wa- 

 ter does not decompose carbonate of baryta, nor the contrary, and 

 when carbonic acid is added to a mixture of lime water and barytic 

 water, carbonates of both those substances are precipitated. 



6. USES. Mr. Parkesf states, that great quantities of the carbo- 

 nate of baryta were formerly exported clandestinely from England to 

 Germany, where it is supposed it was used in the manufacture of 

 porcelain ; it was sold for five dollars a ton. 



Carbonate of baryta is a rather rare production in nature. If it 

 were more common, it might be employed with much advantage in 

 some of the arts as, to afford baryta, which, in building, would form 

 a stronger cement than lime, and to decompose some of the com- 

 pound salts. Pure baryta in solution, will separate the carbonic acid 

 entirely from a solution of carbonate of potassa or soda, and leave 

 the alkali caustic. . 



CARBONATE OP STRONTIA. 



1. DISCOVERY. Jit first confounded with the preceding ; the dif- 

 ference suspected by Dr. Crawford, was proved by Dr. Hope.J 



2. PREPARATION. 



(a.) By adding liquid carbonic acid to a solution of strontia, the 

 precipitate, is again soluble in an excess of carbonic acid, and is 

 thrown down by more of the earth, and so on in the same way as that 

 mentioned under the carbonates of lime and of baryta. 



(b.) By the various methods already indicated, for the formation 

 of a carbonate of baryta, strontia being of course substituted. 



The native carbonate, although a very rare production, is com- 

 monly used in laboratories ; it is found at Strontian, in Argyleshire, 

 and at Lead Hills, in Scotland, &c. 



3. PROPERTIES. 



(a.) The native carbonate has ajibrous and columnar texture, and 

 the cavities are usually lined with crystals, which are generally trans- 

 lucent; the color is green or greenish ; sp. gr. 3.55 or 3.66 ; does 

 not fire with steel 5 it is softer than the fluate, although harder than 



Parkes. t Essays, Vol. 1, p. 327. \ Vide Edin. Trans. 1793. 



