66 liquify into the Laws of JJinity, 



3. The exchange of bafes has been infered merely from the refult of the precipitation 

 and cryftallifation which have been obferved ; but this cfFe£l: has not been attributed to its 

 real caufe. 



In Art. V. it has been fliewn that the forCe of cohefion determines the feparation which, 

 in the elective affinities, takes place by precipitation or cryftallifation. It is alfo the fame 

 force which produces the fame efte£l in the complex affinities. When I mix the folution 

 of fulphate of pot-afh with that of the muriate of lime, the quantity of water not being 

 great, the lime, in its conta£l with the fulphuric acid (No. 1), is fubjefl to the effe£l of 

 the force of cohefion in a higher degree than the pot-afli. Thus a new force is added to 

 thofe which previoufly exifted ; and this muft determine the combination of the fulphuric 

 acid with the lime, at the fame time as its precipitation. 



4. If we take a rapid view of all the known decompofitions which are owing to the 

 complex affinities, and we fhall fee that it is always to the fubftances which have the pro- 

 perty of forming a precipitate, or a fait that may be feparated by cryftallifation, that an 

 excefs of affinity has been attributed beyond thofe oppofed to them : fo that we may 

 foretel by the degree of folubility of the falts which are formed in a liquid, which arc 

 the fubftances of which Bergman and other learned chemifts have pretended to reprefent 

 the forces in their fymbolical tables, by always attributing a fuperiority of affinity to the 

 two fubftances which are difpofed to form an infoluble combination relative to the quantity 

 of the folvent. 



Lime, magnefia, barites, and ftrontlan, form, with the carbonic acid, infoluble falts j 

 all the foluble combinations of thefe earths, when mixed with carbonates of alkalis, produce 

 an exchange, from which the formation and precipitation of carbonates \yith earthy bafes 

 refult. 



Barites forms, with the fulphuric aeid, an infoluble fait. Every time the folution of a 

 fulphate is mixed with that of a fait with bafc of barites, a fait having a fimilar bafe, is 

 formed and precipitated. 



As lime makes a fparingly foluble fulphate, which is in a great meafure precipitated, if 

 there be not much water, it alfo changes its bafe with all the foluble fulphates, till the 

 period when precipitation ceafes, by the folubility of the fulphate of lime. The fulphate 

 of lime being ftill more foluble than the fulphate of barites, the more foluble falts with 

 bafe of barites decompofe the fulphate of lime. 



The oxide of filver forms an infoluble fait with the muriatic acid : all the falts of filver 

 which are foluble, being mixed with foluble muriates, the muriate of filver is precipitated. 

 Mercury, which is not too much oxided, a£ts in the fame manner. 



As the muriate of lead is fcarcely foluble, the falts which the oxide of lead forms with 

 the other acids, and which poflefs folubility, produce a precipitate with the foluble 

 muriates; but as it makes an infoluble fait with the fulphuric acid, the folution of muriate 

 of lead affords a precipitate of fulphate of lead, when mixed with foluble fulphates. 



5. When 



