cto the Mature of precipitates. 195 



Let us now obferve the ufe Mr. Henry made of the pruffiate 

 efpotamthiis prepared to refolve the controverted que ftion. 

 '- He poured foriie of it into a folution of muriate of barites. The purepruf- 

 No precipitation followed ; the mixture was not in the lead 5* tc °^ pota * . 



r . . r 7 dul not precipt- 



difturbed, and he was inclined to think with Meyer and Klap- tate the muriate 

 roth that a pure pruffiate does not precipitate barites. ° f ^ antes aC 



But having obferved the mixture half an hour afterwards, but ft did in half 

 he perceived fmall cryftals forming on the fides of the veffel ; an hour ' 

 and at the end of fome hours they were confiderably aug- 

 mented. 



Thefe cryflals when examined prefented the following cha- 

 faclers : 



1. They are very fparingly foluble in cold water; one Character of the 

 ounce is required to diffolve a quarter of a grain *. precipitated cry - 



2. Warm water diffolves them rather quicker, though in a 

 very fmall proportion. 



3. Thefe folutions afford with fulphuric acid and fulphate of They were un- 

 potafli a precipitate of fulphate of barites; and Pruffian blue ^o^tedly pruf- 

 , . , r , . r- fiate of baritei.^ 

 lvitli lulphate or iron. 



4. Thefe cryflals are completely diffolved in muriatic acid 

 diluted with water, and this folution afforded unequivocal 

 figns of the prefence of pruffiate of barites. 



5. Thefe cryftals heated to rednefs in a filver crucible be- 

 came black/ and loft their form ; muriatic acid poured on the 

 coaly refidue produced an effervefcence, and muriate of ba- 

 stes was formed. 



Mr. Henry draws feveral confequences from thefe fa6ts. Inductions from 

 Thvjirjl, that he was deceived, as well as thofe who an- tht * e fa ^ 8 * 

 nounced, that pure barites does not decompofe pruffiate of 

 potato. 



The fecond, that barites ought to be placed before potato in 

 the column of affinities of pruffic acid. 



The third, that the precipitation effected by pruffiate of 

 potafli" in a folution of muriate of barites, is the product of a 

 double affinity. 



The fourth, that barites differs in this refpeel from the other 

 rarths, and approaches the metals. 



Of thefe four propofitions, the three firft feem to me to be 

 •pen to no objection ; for though Mr. Henry does not relate 



* As the Engliih ounce is here fpoken-of, which contains 4SQ 

 grains, cold water only diifolves about 0,0005 of its weight.— G. 



O 2 any 



