Sa Mr Connell an the Chemical Constitution of Brewsterite. 



analysis that the strontia occurs in the mineral as a silicate, and 

 in such quantity as to constitute an essential constituent ; be- 

 cause that earih had not hitherto been found in nature, except 

 as a sulphate, or carbonate *. 



The specimen of Brewsterite which was the subject of the 

 following researches, consisted of a kind of concretion of the 

 mineral, partly in crystals, and partly in an amorphous state. 

 Previous to analysis, it was submitted, in the condition of frag- 

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

 the purpose of removing any soluble foreign matter. 



25'15 grains of the mineral, in the state of fragments, lost, 

 by ignition, in a platinum crucible, and charcoal fire, 3*16 

 grains, equivalent to 12-584 per cent. 



48-34 grains, in impalpable powder, were fused over the spirit 

 lamp, with about three times their weight of a mixture of 5 

 parts of carbonate of potassa and 4 parts of carbonate of soda, 

 care being taken to employ carbonates free from any sulphate. 

 The mass, after being softened by water, was dissolved in dilute 

 muriatic acid, and the silica separated in the usual manner. 

 The silica, after being ignited and weighed, was dissolved in 

 boiling potash-ley, and left a little residue, which appeared to 

 be undecomposed mineral, and was subtracted from the quan- 

 tity under analysis. 



The residual solution, separated from the silica, was precipi- 

 tated by ammonia. From the precipitate thus obtained, a little 

 silica and oxide of iron were separated by the agency of muria- 

 tic acid, and subsequently of caustic potash in excess. A quan- 

 tity of alumina was then got, by supersaturating the alkaline 

 solution with muriatic acid, and precipitating by carbonate of 

 ammonia. The alumina was ignited, and weighed. 



The liquid which had been precipitated by ammonia was 

 concentrated by evaporation, and carbonate of ammonia was 

 added to it whilst hot. A white precipitate fell, which, after 

 being collected and washed, was dissolved in dilute nitric acid. 

 The solution by evaporation gave a crystalline residue, showing 



• Baryta, besides occurrinpr in its usual natural states, and as a silicate in 

 some varieties of harmotome, occurs apparently in combination with oxide 

 of manganese in some of the ores of that metal, as has been shewn by Kla- 

 proth and Dr Turner. 



