I^O Keparchii refpcSling 



the quantities as on the affinities of the fubftanccs, is, that it 

 is fufiicient to var)' the quantities to obtain oppofite refults." 



•IV, Of the Modificatiom of the Chemical ABion which aftfs 

 frovi the hifoluhil'xty of Suhjlances, 



The author fucceflively cxarjiined the aflfedions of bodies 

 which ipay difj^uifg or alt^r the modifications of ihe principle 

 ellabliflied in the preceding articles. He proves, by a number 

 of experiments, jll. The riianner in which an infoluble fub- 

 fiance a6ls when oppofed to a combinatio^ : ^d. If a fub* 

 fiance has any folubility, its a6lion is compofed of that of the 

 part diflblved and of that which retains its folidity : 3d, That 

 if an infohible combination be attacked by a liquid fubftance, 

 the inconveniences of infolubility foon difappear, when it is 

 fufficient that the infoluble fubftance fhould lofq ^ part of its 

 eonftltuent principles to become liquid. 



The author tfien proceeds to the examination of the dif- 

 ference of the fpecific gravity between the infoluble and li? 

 quid fuhftancp. According to him, it has an influence on 

 their refpe6live a<Stion, even when agitation and heat are em- 

 ployed, becaufe it continually tends to feparate the infoluble 

 fubftance, and to withdraw it from the force oppofed to it : 

 thus there is a difference in this refpe^i betweej> the fulphat 

 of barytes and alumine. 



In ihe laft place, if infolubility prevents the proportion^ 

 which ought to refult from the oppofite forces from being 

 e(labli{l>ed, it occafions flownefs in thofe which can be efta-r^ 

 bliihed ; and it may eafily give rife to deception by the ap- 

 pearances which it produces at the commencement of an 

 operation, fuch as when concentrated fulphuric acid is mixed 

 with a folutiou of potafh, or any other fait that requires a large 

 portion of water to diftblvcit: the acid immediately com- 

 bines with the water, and the fait, which lofes its liquidity, 

 is precipitated ; but, by prolonging the operation and mul- 

 tiplying the oonta^, the fait diflblves, and enters \nto com-., 

 binatign with the liquid. 



V. Of Cohejion and CrjJlalJifation, 

 The CQbefion of the moleculae of a body is owing i.o the 

 reciprocal af^ini^y of th^f? moleculap ; it is a foiqe which muii? 



■ be 



