Inquiry into the Laws of j4£lniiy. 151 



nitrate of lime and the nitrate of pot-alh which formed the uncryftallizable liquid, mu» 

 tually experienced a degree of faturation, which confiderably wealcened their adtion upon 

 the fulphate of lime. 



4. From thefe confiderations, I (hall proceed to deduce firft, the theory of the uncryftal- 

 lizable refidues which are found in the folutions of falts which are evaporated: it will be 

 confirmed by the fucceeding obfervations. 



Saline fubftances exercife upon each other an a£tion which increafes their folubility, an 

 effeft that has been particularly eftablifhed by the experiments publilhed by my learned 

 colleague Vauquelin {Atwales de Chimie, tom. xiii.) This mutual aftion varies in the 

 different falts. It has however been thought, that falts with an earthy bafe do not increafe 

 the folubility of the nitrate of pot-alh, though thefe in reality increafe it the moft. 



There Is doubtlefs in this refpeft, a difference in the effeft produced by the falts, which 

 depends on their nature ; but this difference is in general very fmall, compared with that 

 which proceeds from the force of cryftallization. 



Experiment D. A mixture of equal parts of nitrate of pot-afli and fulphate of pot-afli^ 

 afforded by evaporation, fucceffively and in proportion to their folubility, fulphate of pot-afh 

 and nitrate of pot-afh, without leaving any uncryftallizable liquid ; but the fame experi- 

 ment being made with a mixture of nitrate of foda and fulphate of foda, both of which 

 have only a flight tendency to cryftallize, and are nearly of equal folubility, only a fmall 

 quantity of fulphate of foda is feparated by cryftallization, all the reft remaining liquid, 

 without any cryftallization. A mixture of muriate of foda and fulphate of aluminc having 

 been fubmitted to the fame proof, it was clearly perceived that the two falts had become 

 more foluble ; but they were intirely feparated by the alternate evaporation and cooling. 



It is therefore feen that fubftances which poffefs a confiderable force of cryftallization, 

 though rendered more foluble, feparate on account of their infolubility, and leave very 

 little or no uncryftallizable refiduum. 



But when falts are found which have only a feeble difpofition to cryftallize, their mutual 

 aftion counterbalances their force of cryftallization, fo that there then remains much liquid 

 which eannot cryftallize -, and this happens particularly when the refiduum contains a fub- 

 ftance in itfelf uncryftallizable ; as in experiment C, where by the proportions employed, 

 there was found a fuperabundance of nitrate of lime, which by its a£tion upon the nitrate 

 of pot-alh reduced a confiderable quantity of that fait into an uncryftallizable liquid. 



Whence therefore does it happen, that the moft learned chemifts, Lavoifier, Fourcroy, 

 Vauquelin, Guyton, and the Commiffaries of the Academy of Sciences, among whom 

 myfelf was one, could have been led by the experiments made upon the proof of falt-petre, 

 to believe, that the nitrate of lime exerts no aftion upon the nitrate of pot-alh, nor in- 

 creafed its folubility ? {^nn. de Chimie, tom. xi. xiii. xv. xxiii.) It was becaufe, in the 

 experiments that were made, a water of nitrate of pot alh was put to digeft upon dried 

 nitrate of lime. The latter neceffarily caufed a divifion of the water u^on which it has a 



ftrong 



