-274 ANALYMI CWP JUKJKESITE. 



Muriatic solu* €, To the tecond solution of experiment b a little more 

 *J°[* P"®'P'^** muriatic. and wa» added, and it was then supersaturated with 

 monia. ammonia. This threw down a reddish precipitate, which, 



■ when well dried, weighed a grain ; but by exposure to a red 

 Beat it was reduced to half a grain. By a separate experi- 

 ment this was found to be alumine, containing oxide of iron 

 and manganese. These oxides we separated by di^olving 

 in nitric acid the reddish rehiduum left by the stone after 

 being heated redhot. The weight amounted to a quarter 

 ofag^in. On afterward supersaturating the nitric solu- 

 tion with ammonia, a few flocks of alumine were obtained, 

 ifhich were colourless. 

 Itecotnponeat From the preceding analysis it appears, that this stone id 

 ^"*** an anhydrous carbonate of magnesia, containing a few 



^ atoms of lime, alumine, oxide of iron, and oxide of manga- 



nese, which appear to give it its colour. The proportions of 

 this stone, and the pretty considerable hardness it possesses, 

 are surprising. It contains in 100 parts 



Magnesia • 49 



Carbonic acid • 52 



100. 



*Artificial car- From the properties of this stone it appears, that nature 



bonateofmag* possesses peculiar means of producing anhydrous carbonate 



containr*^* of magnesia : for, from the experiments I have made and 



water, though published in TrommsdorfF*s Journal, the principles of car- 



iiffer"^**' °"' bonate of magnesia may vary, according to the mode in 



which it is prepared, but in all cases it contains a large 



quantity of water. If a solution of sulphate of magnesia be 



precipitated cold by subcarbonate of soda, we always ob» 



tain a carbonate formed of 



w%»en precipi. Magnesia 33 



tatedcold. Carbonic acid 32 



Water •••» * 35 



JOG. 



Tn this process a large quantity of subcarbonate of soda 



* must tje employed, because part of it passes to the state of 



^parbonate ; but then the carbonate of magnesia obtained it 



•T > . the 



