.SODIUM CHLOBIDE BERTHOLLET'S LAWS 435 



to n, the mass of the salt MX would not have any influence oa the 

 modus oper.andi of the reaction, which is equally in accordance with 

 the teaching of Bergmann, who supposed double reactions to be inde- 

 pendent of the mass and determined by affinity only. If M had more 

 affinity 'for X than for Y, and N more affinity for Y than for X, then. 

 according to Bergmann there would be no decomposition whatever, and 

 x would equal 0. If the affinity of M for Y and of N for X were greater 

 than those in the original grouping, then the affinity of M for X and of N 

 for Y would be overcome, and, according to Bergmann's doctrine, complete 

 interchange would take place i.e. x would equal n. According to 

 Berthollet's teaching, a distribution of M and N between X and Y will 

 take place in every case, not only in proportion to the degrees of 

 affinity, but also in proportion to the masses, so that with a small affinity 

 ,nd a large mass the same action can be produced as with a large affinity 

 and a small mass. Therefore, (I) x will always be less than n and 



their ratio * less than unity that is, the decomposition will be ex- 



pressed by the equation,. mMX -f nNY = (ra cc)MX + (n rc)NY 

 + #NX ; (2) by increasing the mass m we increase the de- 



composition that is, we increase x and the" ratio / - r, until with 



(n -x) 



an infinitely large quantity m the fraction will equal 1, and the de 



n 



composition will be complete, however small the affinities uniting MY 

 and NX may be ; and (3) if m = n, by taking MX + NY or MY + NX 

 we arrive at one and the same system in either case : (n x) M2C 

 4- (n #)NY + aMY 4- a;NX. These direct consequences of Ber- 

 thollet's teaching are verified by experience. Thus, for example, a 

 mixture of solutions of sodium nitrate and potassium chloride in all 

 cases has entirely the same properties as a mixture of solutions of 

 potassium nitrate and sodium chloride, of course on condition that the 

 mixed solutions are of identical elementary composition. But this 

 identity of properties might either proceed from one system of salts 

 passing entirely into the other (Bergmann's hypothesis) in conformity 

 with the predominating affinities (for instance, from KC1 + NaNOj 

 there might arise KN0 3 -f NaCl, if it be admitted that the affinities of 

 the elements as combined in the latter system are greater than in the 

 former) ; or, on the other hand, it might be because both systems by 

 the interchange of a portion of their elements give one and the same 

 state of equilibrium, as according to Berthollet's teaching. Experi- 

 ment proves the latter hypothesis to be the true one. But before 

 citing the most historically important experiments verifying Berthollet's 



