434 Dr. Henri/ on a Siliciferous Subsulphate of Alumine. [June 



muriatic acid gave, with muriate of barytes, a precipitate 

 weighing 8*2 gr. equivalent nearly to 3 gr. of real sulphuric 

 acid, which are capable of saturating 1*2 gr. of alumine, suppos- 

 ing with Berzelius that in alum 10*80 alumine are united with 

 26*13 sulphuric acid. 



4. Solution of caustic potash in considerable excess, boiled 

 in 100 gr. of the hydrate, did not dissolve the whole. There 

 remained, in the form of light flocculi, a substance, which, when 

 collected, washed, and ignited, weighed 2*6 gr. and had the 

 characters of silica. 



Alumine, silica, and sulphuric acid, with a large proportion of 

 water, are the only ingredients discoverable in this substance, if 

 we except a mere trace of lime, probably existing in the state of 

 sulphate, which was discovered in its solutions by the agency of 

 oxalate of ammonia. The proportions of its components may be 

 stated as follows : 



Water 88*1 



Alumine 6*5 



Sulphuric acid 3*0 



Silica 2*4 



100*0 



The quantity of alumine found in the hydrate by analysis 

 being equivalent to the saturation of more than five times the 

 sulphuric acid discovered in it, the principal ingredient may be 

 considered as a subsulphate of alumine. To this may be added 

 the epithet siliciferous, applied by M. Lelievre to a somewhat 

 similar mineral, which was discovered by him on the banks of 

 the Oo, in the Pyrenees, and which yielded, on analysis, 44^. 

 alumine, 40-} water, and 15 silex, but no sulphuric acid. To 

 this mineral he has given the name of siliciferous hydrate of 

 alumine.* 



No water, I was informed, occurs in actual contact with the 

 substance of which I have given an account ; but Mr. Chippen- 

 dale, at my request, has sent me a specimen of the nearest that 

 could be found in the mine. The characteristic ingredient of 

 this water is sulphate of iron, with which it is distinctly impreg- 

 nated, and which is probably the agent employed by nature in 

 decomposing the argillaceous stratum, that has given origin to 

 the subsulphate of alumine. 



* Ann. de Chim. et Phys. vi. 333. 



