SODIUM CHLOKIDE -BERTHOLLETS LA AYS 425 



equivalent to each other- that is, as capable of replacing each other * in 

 toto,' as Na or K, ^ Ca or ^Mg (bivalent elements), replace hydrogen. 

 And as, according to Berthollet's doctrine, when mMX of one salt 

 comes into contact with nNY of another salt a certain quantity xMY 

 and ccNX is formed, therefore there remains m x of the salt MX, and 

 n x of the salt XY. If m be greater than HJ and the mass of M and 

 N and X and Y be equivalent, then the maximum interchange could 

 lead to x=n, whilst from the salts taken there would ensue nMY + 

 nNX 4- (m n)MX that is, a portion of one of the salts taken would 

 remain unchanged only because the reaction could only proceed 

 between wMX and nNY. If x were actually equal to n or 0, the mass 

 of the salt MX would not have any influence on the modus operandi of 

 the reaction, which is essentially according to the teaching of Bergman, 

 who supposed double reactions to be independent of the mass but deter- 

 mined by affinity only. If M had more affinity to X than to Y, and N 

 more affinity to Y than to X, then, according to Bergman, there would 

 be no decomposition whatever, and x would equal 0. If the affinity 

 of M to Y and of N to X were greater than in the original grouping, 

 then the affinities of M for X and of N for Y would act, and, according 

 to Bergman'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 measure of affinity, but also in proportion to the mass, 

 so that with a small affinity and a large mass the same action can be 

 produced as with a large affinity and a small mass. Therefore, (1) x 



will always be less than n and their ratio - less than unity that is, 



n 



the decomposition will be expressed by the equation, mMX + nN Y = 

 (m x)MX + (n a)NY + #MY + #NX ; (2) by increasing the massm. 

 we increase the decomposition that is, the measure of x and the ratio 



^ until with an infinitely large quantity m the fraction - will 

 (TL x) n 



equal 1 and the fraction - ^ be infinite, and the decomposition will 



(n-x) 



be complete, however small the affinities 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 both cases : (n cc)MX + (n x)N Y + cc'MY + ccNX. 

 These direct consequences of Berthollet's teaching are verified in reality. 

 Thus, for example, a mixture of the solutions of sodium nitrate and 

 potassium chloride in all cases has the same sum of properties as a 

 mixture composed of the solutions of potassium nitrate and sodium 

 chloride, naturally under the condition of the mixed solutions being of 



