444 On the Cause of Chemical Proportions. [Dec. 



B, which exists in the solution. If it has the strongest affinities, 

 it combines with a greater proportion of C than B does : but 

 though the attractions between A and C be greater tlian those 

 between B and C, A is not able to draw to itself the whole of 



C, to the exclusion of B. In such a case, the portion of C 

 combined with A to that combined with B will be deter- 

 mined by the strength of the affinity, and by the proportion 

 of each present in the solution. Any person may satisfy himself 

 of the reality of this division of C, by pouring concentrated 

 muriatic acid into a solution of sulphate of copper. The solution, 

 which was formerly blue, acquires a green colour by the addition 

 of the muriatic acid (for muriate of copper is green) ; and this 

 colour becomes stronger the more muriatic acid is added. The 

 cause of this phenomenon is, that the affinity of the muriatic 

 acidj though the weaker, still continues to act, and acts with 

 more intensity the greater the quantity of that acid present. If, 

 for example, 100 parts of sulphuric acid, and 100 parts of 

 muriatic acid, divide 100 parts of oxide of copper between 

 them, so that the sulphuric acid takes 80 parts, and the muriatic 

 20 parts, it is clear that the force with which 100 of sulphuric 

 acid remain in combination with SO of oxide is equal to the 

 force with which 100 muriatic acid remain in combination with 

 20 of oxide; that is to say, that the two opposite forces are in 

 equilibrio. If any one of these, combinations should separate 

 from the solution — if the sulphate of copper, for example, should 

 begin to crystallize ; the phenomena would change. A new 

 force, crystallization, would be added. This force does not act 

 merely by abstracting a part of the chemical mass, but likewise 

 as a positive force, capable of counterbalancing and of being 

 counterbalanced. 



It is obvious that in all this there is nothing inconsistent with 

 the laws of chemical proportions. But it will be said that the 

 100 parts of sulphuric acid combined with the 80 parts of oxide 

 of copper, and the 100 of muriatic acid with the 20, are not 

 combined according to the laws of chemical proportions. It is 

 obvious that the surplus of each of these acids is employed in 

 counterbalancing the surplus of its antagonist, and cannot be 

 considered as combined with the oxide of copper. Of conse- 

 quence, the part of each acid really combined with the oxide is 

 neutralized according to the laws of chemical proportions. I 

 conceive that this single example is sufficient to show that the 

 principles of Berthollet's theory are not inconsistent with the 

 laws of chemical proportions. 



II. On the Cause of Chemical Proportions. 

 The fact that bodies combine in definite proportions when 

 other forces do not oppose their re-union, added to the obscrva- 



