' • Inquiry into tfie Laws of ^ffmty. fyj 



and how far diftaht from trufh the eftablifhed opinion 15, that'a complete chtiVige of 'bafe$ 

 takes place on the mixture of muriate of magnefia and the fulphateof pot-afti. 



In experiment M, where the fulphuric acid was prefent in greater proportion, fulphatc 

 of pot-afli was obtained in both the firft cryftallizations ; but in experiment N, where the 

 muriatic acid had more influence by its relative quantity, fulphate of pot-afii was obtained 

 only in the firft cryftaliization ; the magnefia, for the moft part, ren^ained in the un- 

 cryftallizable refidue, becaufe it has no force of cryftaliization with the muriatic acid, and 

 only a weak power with the fulphuric acid ; other falts which would in other circumft.iiices 

 have been cryftallizable, are retained in the refidue which oppofes their cryftallizatibn. 



The difFerende obferved between the refults of thefe two experiments, and'thofe of the 

 experiments A, B, and C, in which a deliquefcent calcareous fait was put intb aftiort 

 with the fulphate of pot-afh, correfponds exadlly with the difference of folubility which 

 exifts between the fulphatc of lime and the fulphate of magnefia. 



9. After having treated of faline fubftances in the preceding experiments, as If they 

 formed feparate or diftindl combinations in a liquid, I fliall now confider fome effefls 

 which are owing to the mutual adlion which is in reality exerted by them all when they 

 are mixed in this ftate. 



Expi'riment O. Aqueous folutlon of the acetite of lead was gradually poured into a folu-' 

 tjon of muriate of foda, till no more precipitate was produced. The liquid which remained 

 above the precipitate ftrongly reddened blue paper, which efFeft was not produced by the 

 mere folution of the acetite of lead, nor by the muriate of foda ; But it aflumed a deep 

 colour with the hydro- fulphurets, and afforded an abundant precipitate with the muriatic 

 and fulphuric acids. During its evaporation a depofition was formed of a fcarcely foluble 

 muriate of lead, and alfo a cruft which had not a cryftalline appearance, and which will be 

 fpoken of hereafter. Laftly, fome fine cryftals were obtained, which were an acetite of 

 foda, and an oxide of lead. On diflblving the faline cruft, a depofition took place of 

 muriate of lead with excefs of oxide, analogous to that defcribed by Vauquelin {Aniiales 

 de Chitnie, t. xxxi.) It was neceflary to repeat the folution and cryftaliization feveral 

 times, before the depdfirion ceafed. The faline cruft was thus, or at this period, divided 

 initj two fubftances, muriate of foda, and muriate of lead. 



If the muriatic acid remain engaged in the acid together with the acetous, as both acidi 

 are volatile, the excefs which is but flightly engaged, and which may be expelled by the 

 aftion of heat, muft be compofed of two acids. In fa£l, having diftilled a mixture fimilar 

 to the preceding, after having feparated the depofition which was firft formed, the liquid 

 which paffed into the receiver contained acetous and muriatic acid ; this circumftance 

 dcferves particular attention, and ferves to explain feveral obfervations. 



10. Citizen Prieur has obferved that when lead is employed for purifying the folution of 

 filver mixed with muriatic acid, a part of the laft-mentioned acid paffed over by diftilla- 

 tion. This happens becaufe the muriate of lead is foluble, and even very much fo by the 

 action of the nitric acid. The liquid is therefore compofed of oxide of lead, muriatic acid 



X 2 and 



