356 Mr Connell on the Chemical Constitution of' Brewsteritc. 



with well formed crystals of the mineral. The portions of it 

 examined were first exposed in small fragments to the action of 

 largely diluted muriatic acid, to remove any calcareous spar or 

 other matter soluble in such a menstruum. The decomposition 

 was then effected by means oi carbonate of soda, as the action of 

 strong muriatic acid, although considerable, seemed not com- 

 plete. Thinking it possible that the baryta and strontia might 

 have been mingled, in some form or other, as impurities in the 

 less perfectly crystallized portions of the mineral, I selected 

 from a different specimen, a small quantity of well formed crys- 

 tals of Brewsterite, with some small portions, which appeared 

 to be fragments of crystals, my object being to avoid amorphous 

 matter as much as possible. What I thus selected was first ex- 

 posed to the action of water, acidulated with muriatic acid, for 

 the same reason as before. It was then reduced to fine powder, 

 and fused in platinum foil over the spirit-lamp, with a mixture 

 of the carbonates of soda and potassa. After separating silica 

 in the usual manner, and precipitating by ammonia, carbonate 

 of potassa was added to the residual liquid, and the whole eva- 

 porated to dryness. Whatever was soluble was then removed 

 by water. The residue, after being washed and ignited, dis- 

 solved with effervescence in dilute nitric acid, leaving a very 

 slight dark residue. The solution by spontaneous evaporation, 

 gave white crystals, which were chiefly thickish tables, and were 

 not altered by exposure to the air. There was hardly any trace 

 of deliquescent matter, shewing that the mineral could contain 

 no notable quantity of lime, an observation perfectly supported 

 by my examination of the other specimen. The crystals were 

 next folded in platinum foil, and ignited over the spirit-lamp, 

 to drive off the nitric acid. The residuum, which was dark 

 coloured, was dissolved in dilute muriatic acid. The solution 

 was set to evaporate spontaneously, and gave a mixture of tabu- 

 lar and of long prismatic crystals, partially coloured yellow, as 

 by a salt of iron. The prismatic crystals were taken up by hot 

 alcohol, and recrystallized from a watery solution. Both the 

 tabular and the prismatic crystals, by ignition, became darkish, 

 and when redissolved in water, left a dark coloured residue, 

 which seemed, to a great extent, insoluble in muriatic acid, and 

 gave traces of iron. The watery solutions, when recrystallized, 



