WRITINGS OF JAMES SMITHSON. 81 



snow and that of hail, the hail which falls partakes of the 

 nature of both, is partly the one and the other ; its crystals, 

 though regular, arc opaque, of little solidity, and consist, 

 like snow, of an imperfect union of grains, or smaller 

 crystals. 



A MEANS OF DISCRIMINATION BETWEEN THE 

 SULPHATES OF BARIUM AND STRONTIUM. 



From Thomson's Annals of Philosophy, Vol. XXI ; New Series, Vol. 

 V, 1823, pago359. 



April 2, 1823. 



SIR : To distinguish barytes and strontian from one an- 

 other, it is directed in No. 19 of the Journal of the Royal 

 Institution to dissolve in an acid which forms a soluble salt 

 with them, to decompose by sulphate of soda, and to add 

 subcarbonate of potash to the filtered liquor. If the earth 

 tried is strontian, a precipitate falls ; if barytes, not. 



When these matters are in a state to be soluble in an acid, 

 a more certain, I apprehend, and undoubtedly a much easier 

 proceeding, is to put a particle into a drop of marine acid 

 on a plate of glass, and to let this solution crystallize spon- 

 taneously. The crystals of chloride of barium in rectangu- 

 lar eight-sided plates are immediately distinguishable from 

 the fibrous crystals of chloride of strontium. 



I have not repeated the process above quoted ; but if sul- 

 phate of strontium did possess the solubility in water there 

 implied, this quality presented a ready method by which 

 mineralogists would be enabled to distinguish it from sul- 

 phate of barium. On trial I did not find water, or solution 

 of sulphate of soda, in which sulphate of strontian had long 

 lain, produce the least cloud on the addition of what is 

 called subcarbonate of soda. 



