374? Prof. Johnston o?t the Composition of 



1st. 72*13 grs. dissolved in dilute muriatic acid and the 

 gas made to pass over chloride of calcium, lost 21*18 grs. 

 = 29*363 per cent, of carbonic acid. 



2ndly. 50*57 grs. dissolved in muriatic acid, precipitated 

 by fluo-silicic acid and heated to redness, gave of fluoride of 

 barium 29*18 grs. = 32*996 carbonate of baryta, or 65*24<8 

 per cent. 



The filtered solution was poured into a large quantity of 

 water saturated with sulphate of strontia, and precipitated by 

 sulphuric acid. The precipitate weighed 1*81 gr., and be- 

 sides strontia contained also the small quantity of baryta held 

 in solution by the fluo-silicic acid. If we neglect this small 

 quantity of baryta, we have 1*456 or 2*87— per cent, of car- 

 bonate of strontia. 



A specimen from Bromley Hill, Dr. Thomson's locality, 

 when dissolved in muriatic acid, left 0*16 per cent, of insoluble 

 matter, and gave 29*71 per cent, of carbonic acid. 



36*58 grs. precipitated by fluo-silicic acid gave 20*14 grs. 

 of fluoride = 22*774 or 62*156 per cent, of carbonate of 

 baryta. 



The sulphate of strontia obtained as before, and containing 

 a little baryta, weighed 3*02 = 8*256 percent. = 6*641— car- 

 bonate of strontia. 



33*05 grs. dissolved in muriatic acid largely diluted and 

 precipitated by sulphuric acid, gave of sulphates* 26*84 grs. 



The supernatant solution precipitated by oxalate of am- 

 monia gave 10*01 of carbonate of lime or 30*29 per cent 



The doubly obhque baryto-calcite of Mr. Brooke treated 

 in the same manner gave me of carbonic acid 30*05, of car- 

 bonate of baryta 65*97, and of carbonate of strontia 2*3 1 7 — 

 per cent. 



The following table exhibits these results in connection with 



• I have said sulphates, as it is hardly possible to free the precipitate 

 thus obtained from a trace of lime. It also contained sulphate of strontia. 

 41*27 grs. of the Fallowfield mineral gave me a precipitate weighing 58'88 



grs. (it should be in pure Ba C+Ca C, 56*36). Boiled in nitric acid it lost 

 3*31 grs. ; again boiled 45*94 grs. lost 1*82, and a third time 40*065 grs. 

 lost 0*51. Evaporated to dryness and the dry mass converted into chlo- 

 rides, I obtained a deliquescent chloride of calcium, tabular crystals of 

 chloride of barium, and prismatic crystals giving the characteristic purple 

 flame of chloride of strontium. Though the last portions of lime and 

 strontia therefore may be dissolved out by repeated boiling in dilute nitric 

 acid, it would appear that the sulphate of baryta itself is not wholly inso- 

 luble in this menstruum. 



