1822.] of Two Finnish Minerals, 103 



prisms ; the crystals are large, and generally incrusted with talc, 

 which renders it difficult to measure the angles : the specific 

 gravity is 2* 603. Exposed to the heat of the blowpipe, it 

 becomes paler, and at a higher temperature the thin edges are 

 difficultly fused. It dissolves in borax and microcosmic salt, 

 exhibiting, while coohng, the appearance of iron ; it does not 

 combine with soda ; with the solution of cobalt, it gives a brown 

 colour, verging to blue on the fused edges. By exposure to a 

 high temperature, the loss amounted to 1*65 per cent, and the 

 experiment was repeated with scarcely any variation. The 

 analysis was performed as follows : 



a, 296-2 parts of fragments of this mineral, of a violet blue: 

 colour, were reduced to powder, and levigated in a calcedony^ 

 mortar, with the addition of water. The powder being dried, 

 had not increased in weight, proving that it had gained nothing 

 from the mortar. The powder was heated with 1000 parts of 

 carbonate of potash in a platina crucible, the mass was dissolved 

 in dilute muriatic acid, and evaporated to dryness in a platina 

 dish. It was again digested in muriatic acid, and the silica left 

 weighed, after ignition, 146. 



h. The muriatic solution was decomposed by ammonia, and 

 gave a precipitate which, after washing, was boiled with solu- 

 tion of potash, and then filtered. From this, muriatic acid and 

 carbonate of ammonia separated alumina, which, after washing, 

 was ignited and weighed ; it was then treated with sulphuric 

 acid, which left 1*4 of sihca ; the sulphuric solution upon the 

 addition of potash gave crystals of alum, which contained 96*5 

 of alumina. 



c. The brown precipitate which remained undissolved by the 

 potash was dissolved in muriatic acid, mixed with a little nitric 

 acid, and heated to ebullition. The solution diluted with water 

 was neutralized with ammonia, and precipitated with succinate 

 of ammonia : the precipitate after combustion in an open platina 

 vessel gave 14*8 of peroxide of iron. 



d. The solution freed from iron gave I'O of alumina with car« 

 bonate of ammonia, was then evaporated to dryness, and the 

 muriate of ammonia being separated by heat, it was decomposed 

 by carbonate of potash, and gave a precipitate which after igni- 

 tion weighed 2-0 parts, and by sulphuric acid, 1*9 of magnesia, 

 was dissolved, and 0*1 of oxide of manganese was left. 



e. The solution remaining after precipitation with ammonia, 

 treated with carbonate of potash, heated to ebullition, evaporated 

 to dryness, and again dissolved in water gave a precipitate 

 which, when ignited, weighed 29-8 parts. 



Diluted sulphuric acid left 0-7 of silica, and dissolved 29*1: 

 parts, which were magnesia. This magnesia, and that above: 

 obtained, were found to be pure by means of a solution of cobalt, 

 which imparted its red colour, and by sulphuric acid, which. 

 yielded pure sulphate of magnesia. 



