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less energy than the first," But before this theory can he suf- 

 ficiently esiablishcci, it is necessary to rebut or refute the 

 opinions of Berthollet, who was the first to apply the law of 

 astronomical or physical to chemical attraction. He has en- 

 deavoured to prove that the relations of the force of attraction 

 to quantity are univeisal, and that consequently no such 

 thing as elective affinities, properly so called, can exist. 

 The powers of bodies to combine, he maintains, always de- 

 pend on their relative attractions and their acting masses, 

 whatever these mav be ; and he supposes that in all cases of 

 decomposition, where two bodies act on a third, this third 

 is divided between them in proportion to their relative 

 affinities, and their qiiantities of matter. If this position 

 were correct, there could be no simple law of definite pro- 

 portions. According to this opinion, a salt crystallizing in 

 a strong alkaline solution must be strongly alkaline, in a 

 weak one less alkaline, and in an acid solution it must be 

 acid; which is not the fact. Sir Humphry investigates this 

 important question at considerable length, with his usual 

 aculenejs and perspicuity. He denies the existence of a 

 general law, that the attractions of bodies for each other are 

 inversely as the quantities that saturate. This proposition 

 of Berthollet he reduces to an absurdity. Thus: " inag- 

 nesia and ammotiia take up more sulphuric acid ihan equal 

 quantities of potash ; therefore Berthollet concludes that 

 magnesia and ammonia have a stronger attraction for acids 

 than potash : yet, potash instantly separates magnesia and 

 ammonia from acids ; and though the facility with which 

 ammonia is expelled from a compound may be hypotheti- 

 cally accounted for, by assuming that the case with which 

 it takes the gaseous state assists its escape ; yet magnesia 

 is in an opposite case; and to account for chemical changes 

 by supposing the eflects of forms of matter which are about 

 to appear, or powers not in actual existence, such as elasti- 

 city or cohesion, is merely tlie solution of one difficulty by 

 the creation of another. Ammonia, when solid or fluid, 

 should require a lew force to render it elastic, and the co- 

 hesion, in a compound, can cnily be regarded as the exertion 

 of the chemical attractions of its elements. The action 

 between the constituents of a compound must be mutual 5 

 sulphuric acid, there is every reason to believe, has as much 

 attraction for baryta, as baryta for sulphuric acid; and 

 baryta is ihe alkaline substance, of which the largest quan- 

 tity is requiied to saturate sulphuric acid: therefore, in 

 Beribollet's view, it has the weakest affinity for that acid : 

 but Itss sulphuric acid saturates this substance than any 



other 



