468 Scientific Intelligence. [Juke, 



bodies, aiid there romaincd carbonate of barytes and magnesia, which 

 again were di:>solved by muriatic acid, mixed with sulphuric acid, 

 filtered, evaporated, and heated, and the quantity of magnesia 

 ascertained. 



The alkaline solution, after having been neutralized with sulphuric 

 acid, was evaporated ; during the evaporation, some crystals of boracic 

 acid appeared which were easily dissolved by alcohol. 



The solution of the alkaline sulphate showed by its crystallization 

 . that it contained potash and soda ; the presence of the latter was also 

 clearly shown when the sulphate was converted into a carbonate, and 

 neutralized with bitartrate of potash. Beautiful crystals of tripletar- 

 trate of potash and soda appeared. Dr. Gmelin recommends this 

 method to ascertain the presence of soda in the alkalies from minerals. 



This tourmaline was found to be composed of 



Silica 38-92 



Boracic acid 60 



Alumina » 33-24 



Oxide of iron 7*20 



Magnesia 980 



Potash and soda 253 



Loss by heat 003 



92-32 



A direct analysis by sulphuric acid gave : 



Silica 42-59 



Boracic acid 060 



Alumina 34-32 



Oxide of iron 5 22 



Magnesia 8-47 



Potash and soda 242 



93-62 



The quantity of boracic acid was not ascertained in the latter analysis, 

 and the greater quantity of silica may be easily explained, partly by a 

 small quantity of undecomposed mineral, and partly by the decomposi- 

 tioB of a minute portion of glass. 



To explain the unusually great loss, Dr. Gmelin tried the tourmaline 

 v^ith oxide of copper,, but no trace of carbonic acid appeared. He 

 thought it possible that some earth in the tourmaline might in this 

 combination contain more oxygen than usual ; therefore, he boiled the 

 powder witli concentrated sulphuric acid, but no air, except that of the 

 vessels, appeared. It remains, therefore, still dubious what this sub- 

 stance is which escapes during the analysis, but it may be partly 

 boracic acid, all methods for determining its quantity in minerals being 

 -deficient. Dr. Gmelin proposes as the best method, to heat tourma- 

 line with carbonate of soda, dissolve in water, to precipitate all the 

 earths by carbonate of ammonia, to saturate the solution perfectly by- 

 nitric acid, and then to precipitate the boracic acid with nitrate of 



