j^A Inquiry intQ the Lems.ojfA^nitj,^ 



the leaft in the latter, the nitrate of pot-afli was obtained by the firfl; cryilalllzatlon ; but M 

 in experiment K the muriatic acid exifted in a greater proportion, muriate of pot-a(h only 

 was then obtained : one part of pot-a(h with muriatic acid, nitric acid and lime formed 

 the refiduum. The proportions employed in experiment L, differed little from thofe of I> 

 and the refults were nearly the fame. 



Oppofite combinations therefore are obtained according to the proportions employed, or 

 according to the period of cryftallization ; that is to fay, according to the proportions of 

 the fubftances which remain inaftion, when a fufficient force of coheflon does not exift ia 

 the combinations that might be formed. But according to the opinion adopted by che- 

 mifls, the entire change of bafe which it is affirmed muft take place, may be judged ot 

 even by a firft cryftallization. 



If, for example, nitrate of pot-afli be firft obtained from the proportions which hare 

 been employed of muriate of pot-afli and nitrate of lime, a conclufion is made, that an- 

 exchange of bafe has been effeded between the muriatic and nitric acids. If other pro- 

 portions had been employed which would have afforded muriate of pot>a(h, as. in expert^ 

 ment K, an oppofite confequence would have been drav/n. Chemlfts have even gone far- 

 ther ; from the conclufion refpe£\ing the change of bafe, for example, between the mu-- 

 riatic and nitric acids, a farther inference has been made, that the combinations oppofittt 

 to thofe which afforded fuch a clvange, would not be at all affe£\:ed by their mixture. 



8. I have examined what change, might be produced in the refults by a fubftance whicJ^ 

 has the property of forming triple falts, fuch as magnefia. 



Experiment M. Equal parts of fulphate of pot-a(h and muriate of magnefia, afforded, i. 

 fulphate of pot-afti ; 2. fulphate of pot-afli, a little muriate of pot-afli, and a triple falt,^ 

 compofed of fulphuric acid, pot-afti, and magnefia ; this fait forms fine rhomboids, which, 

 by expofure to the air, do not lofe their tranfparency ; its folubility is nearly the fame as 

 that of the fulphate of pot-a(h : 3. muriate of pot-afli and fulphate of magnefia. The re.- 

 Cduum contained fulphuric acid, muriatic acid, pot-afli, and magnefia. 



Experiment N. Two parts of murate of magnefia, and one of fulphate of pot-afli, 

 afforded, i. fulphate of pot-afti ; 2- muriate of pot-afli, and the triple fait of the preceding 

 experiment ; 3. muriate of pot-aflj, and fulphate of magnefia : the refiduum was analogous 

 to that of the preceding experiment. 



In experiment M, fulphate of pot-afti was obtained by two cryftallizations ; but in expe* 

 riment N, where the muriatic acid was in a greater proportion, it was obtained on the. 

 firft cryftallization ; the triple fait, which in folubility nearly approaches the fulphate ofi 

 pot-afli, cryftallized after the fecond evaporation. When the proportion of fulphuric acid 

 was fufHciently diminiflied by thefe cryftallizations, then the muriate of pot-afli was» 

 feparated, nearly according to the order of folubility ; and laftly the magnefia^ which being 

 ftill abundant, cryft.illizes with part of the fulphuric acid. 



We fee that a different opinion might have been formed in thefe two experiments, ac- 

 cording to the perlpd of the cryftallization to which.the attention njight have been direded, 

 3 and 



