22 Sketch of the Improvements in Science [Jan. 



5. Analyses of Minerals. 

 The number of chemical analyses of minerals which have been 

 made last year, as far as the subject has come under my knowledge, 

 is uncommonly small ; owing, 1 presume, to the unusual agitation 

 of the Continent. 



1 . I have given, in the first Number of the Annals of Philoso- 

 phi/y Gahn's test of alumina in minerals tried before the blow-pipe. 

 It consists in the lively blue colour which such minerals assume 

 when treated with a preparation of cobalt. 



2. Mr. Hatchett has favoured us with a very simple method of 

 separating manganese from iron. It consists in mixing the diluted 

 muriates of these metals with a little ammonia, and then filtering; 

 all the iron remains upon the filter, and the manganese passes 

 through. Ihave given, in the Annals of Philosophy, vol. ii. p. 2/1, 

 several other methods of accomplishing this separation ; but Mr. 

 Hatchett's method has the advantage over them all, in point of 

 facility and cheapness. 



3. Dr. Marcet has proposed nitrate of silver as a most delicate 

 test of arsenic when held in solution : the yellow colour of the 

 precipitate being quite peculiar, and appearing when the minutest 

 traces of arsenic exist. 



4. According to the analysis of Professor Stromeyer, of Gottin- 

 gen, the mineral called konite, which occurs at Meissner, is 

 composed of 



Magnesia 32-388 



Lime 15-160 



Oxide of iron 2-962 



Silica 0-530 



Carbonic acid 48-808 



Volatile matter 0-252 



Or of Carbonate of magnesia .... 68-0S2 



Carbonate of lime 26-719 



Carbonate of iron 4-417 



Silica 0-530 



Volatile matter 0-252 



100-000 



5. Mispickel, or arsenical pyrites, according to Chevreul, is 

 composed of 



Arsenic 43-418 



Iron 84-938 



Sulphur 20-132 



Loss 1-512 



100-000 



