1820.] Dr. Gmeliu's Ana/j/sh ofPefalitc, ^c. 341 



Article VIII. 



Analj/sis of PelaUtc, and ILxamitiation of the Chemical Properties 

 oj Lithia.*' By Dr, C. G, Gmelin, of Tubingen. 



In vol. lix. p. 241, of the Annalen der Physik, there is a 

 description of the external characters of the petalite, and an 

 account of some of its properties by Dr. Clarke.t I shall make 

 the following additions to this description. I found tlie specific 

 gravity of petalite weighed in water of the temperature of ol>^-° 

 = 2-4268. 



When very thin scales of it are exposed to the action of the 

 blow-pipe, they melt easily, and we then perceive with the 

 naked eye that the surface of the melted matter is full of small 

 vesicles. 



The phosphates dissolve it with difficulty. The melted glass 

 bead is transparent as long as it is hot, but on cooling, it becomes 

 opaque. It is colourless, and even the addition of saltpetre 

 (provided the petalite was pure) does not betray the presence of 

 oxide of manganese in it ; which it undoubtedly would do, if 

 petalite contained, according to the statement of Clarke and 

 Holme, 2*5 per cent, of oxide of manganese. 



Borax dissolves it with facility. The bead is transparent and 

 colourless. Carbonate of soda likewise dissolves it with facility. 



1 wished, before undertaking the analysis of petalite, to analyze 

 some of the salts of lithia which are obtained during the analysis 

 of petahte. My first business, therefore, was to obtain sulphate 

 of lithia. 



Some difficulty occurs when we analyze petalite by means of 

 barytes. If we employ carbonate of barytes, it is necessary to 

 mix a very great proportion of it with the petalite ; and even 

 then the decomposition is apt to be incomplete, unless the peta- 

 lite has been reduced to an exceedingly fine powder. M we 

 employ nitrate of barytes, a silver crucible is scarcely able to 

 withstand the degree of heat necessary to produce a complete 

 decomposition. After having examined both methods, it 

 seemed to me most adviseable to expose the mixture of petalite 

 and nitrate of barytes to a red heat in a platinum crucible, though 

 I was aware that platininu is attacked by caustic barytes. 



A portion ofpetalite reduced to a very fine powder by washing 

 was triturated with five times its weight of crystallized nitrate of 

 barvtes, and exposed to a white heat for two hours in a platinum 

 crucible. The mass, when treated with miniatic; acid, appcured 

 to have been completely acted upon ; though, as is conmioqly 



• Tranbliiifci from Gilljrrl\ \i imIpr 'ler I'l)y-,ik, Ivii, 593. 

 + I'luiiblaicd liuBi \.\k Awiah cf rinlo^ophy^ si. 191and3tjj. 



