Analysis of a Man ganesian Garnet. 157 



change of colour clearly proved, that the iron and manga- 

 nese existed in a minimum state of oxidation, therefore, 

 the 0.486 grammes of peroxide of iron must be reduced to 

 the state of protoxide, and are equivalent to 0.448 grammes 

 of protoxide of Iron on 3 grammes, or 14.93 per 100. 



E. The filtered liquor, (D) was boiled with an excess of 

 sub-carbonate of soda, the carbonate of manganese thus pre- 

 cipitated, was washed and strongly calcined, the tritoxide 

 of manganese weighed 1.007 grammes, and on examination 

 was found to contain neither alumina nor iron: the 1.007 

 gr. of tritoxide are equivalent to 929 grammes of protox- 

 ide of manganese on 3 grammes, or 30.96 per 100. 



F. The liquor (C), after filtration was successively tested 

 with oxalate of potash, and with caustic potash, and thus 

 proved to contain neither lime nor magnesia. 



According to the preceding experiments, the constituents 

 of this Garnet are 



per 100 parts, 



A. Water, - - 00.66 containing oxygen 



B. Silica, - - - 35.83 - - 18.02 



C. Alumina, - - 18.06 - - 08.43 



D. Protoxide of Iron, - 14.93 - - 03.39 



E. Do. of Manganese 30.96 - - 06.79 



100.44 18.61 



And its mineralogical formula will be/S4-2mgS-f-2AS. 



Boric acid in Tourmalines. 



To detect the Boric acid in the green Tourmaline, from 

 Chesterfield, Massachusetts, a portion of the mineral was 

 pulverized, and calcined at a red heat, with three parts of 

 caustic potash ; the mixture after calcination, was treated 

 with muriatic acid and evaporated to a dry gelatinous mass, 

 which was afterwards digested in alcohol; the alcoholic so- 

 lution, when ignited, burnt with a beautiful green flame, a 

 proof of the presence of Boric acid ; the same acid was al- 

 so found, by a similar treatment, in the Ruhellite and Indi- 

 colite from Massachusetts, and in the black Tourmalines 

 from Haddam, Connecticut, and Chester creek, Delaware 

 Co. Pa, 



