30 ACCOUNT of a MINERAL 



figures. I continued to pour in potafs as long as any precipi- 

 tation followed, and I certainly- confumed more alkali than 

 would have been fufficient to faturate the whole of the acid. 

 The cryftalline depofite, when dried quickly, effervefced very 

 feebly with muriatic acid ; it was much more abundant than 

 the former ; it weighed 74 grains. From the fupernatant li- 

 quor, carbonate of potafs feparated eflPervefcent Strontites to 

 the amount, when dry, of 132 grains. The matter thrown 

 down by potafs, when diffolved in muriatic acid, cryftallizes in 

 every refpedl like ordinary muriated Strontites. It is alfo fo- 

 luble in water, and generates Strontitic water. From thefe ex- 

 periments it appears, that potafs precipitates only a portion of 

 the Strontites, which is in the ftate of cryftals, and that this 

 portion is variable in quantity, which I imagine in fome mea- 

 fure depends upon the ftate of dilution. How this comes to 

 pafs it is not eafy to fay. I am difpofed to afcribe it either to 

 the produ(5\ion of a triple compound, or to the folubility of 

 Strontites in pure alkali. The weight of the two precipitates, 

 in neither experiment, exadlly amounted to that of the fpar 

 employed ; nor was this to be expelled. In the former it was 

 deficient by fix grains, in the latter it exceeded by as much. 

 The deficit of the one may arife in part from the lofs of matter 

 adhering to the filter, but principally from the heat employed 

 in drying, expelling too much moifture from the firft precipi- 

 tate. A priori, it might be imagined, that there fliould always 

 be a deficiency, fince part of the earth is difengaged in its pure 

 Hate, as invariably happens with lime. Inftead of this, how- 

 ever, in the latter experiment there was rather an increafe of 

 weight. This I impute to the cryftalline form in which the 

 Strontites is feparated ; for in this ftate it is united to a greater 

 weight of water than it contains of both carbonic acid and wa- 

 ter when it is efi^ervefcent. 



73. The impra(5\icability of precipitating all the Strontites 



from muriatic acid, fuggefted fome doubts whether the alkali 



2 really 



