];38 CHEMICAL AFFINITY". 



demonstrated by Berthollet to hold ia every case : thus a givert 

 portion of water is retained more obstinately by a large quantity 

 of sulphuric acid, than by a small quantity. Oxygen is more 

 easily abstracted from those oxides, which are oxidized to a maxi. 

 muni, than from those which are oxidized to a minimum ; that 

 is to say, that a large mass of metal retains a given quantity of 

 oxygen more violently than a small mass. Lime deprives pot. 

 ash of only a portion of its carbonic acid ; and sulphuric acid 

 deprives phosphoric acid of only a portion of the lime with 

 which it is united in phosphate of lime, in these, and many 

 other instances that might be t mum rated, a small portion of one 

 body is retained by a given quantity of another, more strongly 

 than a large quantity. And Berthollet has shewn, that in all 

 cases a large quantity of a body is capable of abstracting a portion 

 of another, from a small portion of a third ; how weak soever the 

 affinity between the first and second of these bodi< s is, and how 

 strong soever the affinity between the second and the third. Thus 

 when equal quantities of the following bodies were boiled together, 

 C Sulphate of barytes f Oxalate of lime 



J Potash ' 1 Potash 



f Sulphate of potash . j Phosphate of lime 



" Soda ' (Potash 



C Sulphate of potash 6 j Carbonate of lime 



Lime ( Potash 



the unoombined base abstracted part of the acid, from the base 

 with which it was previously combined ; though in every one of 

 these instances it was retained by that base, by an affinity consi- 

 dered as stronger. The same division of the base took place when 

 equal quantities of oxalate of lime, and nitric acid, were boiled 

 together. 



We have seen that sensible attraction, though in all cases the 

 same kind of force, is not always the very same force ; for 

 though the mass and the distance of two bodies bn equal, the abso. 

 lute force by which they are attracted towards eaoh other by gra. 

 vitation is not equal to the force by which they are attracted to. 

 wards each other by magnetism. The forces of sensible attraction 

 are three in number, namely, gravitation, magnetism, and elec- 

 tricity ; the first is always the same when the mas* and distance are 

 the same, but the two la^t vary even when the mass and distance 

 continue unaltered. 



