NATIVE CARBONATE OF MAGNESIA. 24i 



very flightly on it ; it Is not reducible to a folid pafie ; yet on 

 drying it appears to agglutinate, and contra6l a little its di- 

 menfions. Its fpecific gravity, when all the bubbles of air it 

 contains have efcaped, is 2.612. In the fire it loft 0.585 of 

 its weight, and became fufficiently hard to fcratch Bohemian 

 glafs flightly. Five grammes, being diflblved in nitric acid, 

 gave out a large quantity of gas, by which the weight was di- 

 miniflied 230 centigrammes. 



Concentrated fulphuric acid, poured on the ftone reduced Effervefces with 

 to powder, occafioned a violent efFervefcence on the addition " ^ ""'^ ^" * 

 of water. Without this addition the efFe6l was not perceptible. 



By this treatment a fait cryftallized in fmall needles was ob- and yields ful- 

 lalned, which difplayed all the properties of fulphate of mag- ^^^^^ ° magne* 

 nefia. 



This fait was precipitated by potafh, and the precipitate, 

 when dried, weighed 131.5 centigrammes. 



The portion not diflblved by fulphuric acid Was pure filex. Contains filex. 

 and weighed 7 1 .2 centigrammes. 



Pruffiat of foda gave the folutions a flight greenilh tinge, but 

 nothing capable of being weighed Was depofited. 



This ftone therefore contains. Its analyfis. 



Magnefia - - 26.3 



Silex - - - 14.2 



Carbonic acid - - 46 



Water - - - 12 



Iron - - - 



Lofs - - - 1.5 



100.0 

 Cit. Guyton obferves, that the difference between the pro- How It differs ] 

 portions of the conftituent fubftances of this ftone, and thofe of ^jgi carbonate. 

 the artificial carbonate of magnefia, arifes no doubt from the 

 clrcumftances in which thefe falts have been produced ; and 

 the other charaderiftics, that diftinguifli them, may be occa- 

 fioned by the prefence of the other fubftances found with the 

 carbonate of magnefia in the ftone of Caftella-Monte, 



Vol. VI.— December, 1803. R Curiau.i 



