4-2H 



sodium sulphate and zinc chloride were taken, tin- precipitate pre- 

 sented tin- sail if con i posit ion as 1 if fore I hat is. about -^ per cent, of the 

 -alts taken had been subjected to decomposition. In a similar experi- 

 ment with a mixture <if .sodium chloride and magnesium sulphate. 

 L'XaCl -f- MgS( >,, about half of the metals were subjected to decompo- 

 sition, which may be expressed by the equation 1 Na( '1 -f L'MgSO , 

 L'Xat'l + .MgSc > 4 -f Xa,,SO.j + MgCl, = L ) Xa,S(J 1 ^L ) Mo-Cl,. A no less 

 clear limit expressed itself in other of .Mala^ut i's researches when lie 

 investigated the above-mentioned reversible reactions <f the insoluble 

 salts of barium. When, for example, barium carbonate and sodium 

 sulphate ( l'..i( '< )., -f- Na.^Sf >,) were taken, t lu-n about 7l' percent, of the 

 >alts were decomposed, that is. were converted into barium sulphate 

 and sodium carbonate. JUit when the two latter salts were taken, 

 then about 111 per cent, of the salts passed into barium carbonate 

 and -odium sulphate. Probably the end of the reaction was not 

 reached in cither case, because this would require a u'lvat time and a 

 ditlicultly attainable uniformity of conditions. 



(Gladstone (1S.V>) took advantage of the colour of solutions of 

 different ferric salts for determining the measure of exchange between 

 metals. Thus u solution of ferric thioeyanate has an exceedingly 

 intense red colour, and by making a comparison between the colour of 

 the resulting solutions and the colour of solutions of known strength 

 it was possible to judge to a certain degree the quantity of the 

 thioeyanate formed. This colorinietrie method of determination has 

 an important significance 1 as being the first in which a method was ap- 

 plied for determining the composition of a solution without the removal 

 of any of it s component parts. When Gladstone took equivalent quanti- 

 ties of ferric nitrate and potassium thiocvanate I'Y(X< ).,). { -f- .">KCXS 



then on'v 1 -I pel* cent, of the salts were subjected to decomposition. 

 ( >n increasing the mass of the latter salt the quantity of ferric thio- 

 eyanate formed increased, but even when more than )>00 equivalents of 

 pota>sium thioeyanate were taken a portion of the iron still remained 

 as nitrate. It U e\ ident that the atlinitv acting between I'Y and 

 N ( >,and between |\ ;uid ('NS on the one hand is greater than the 

 aflinit ies act ing between I'V and('NS, together with t he atlinit \' of 1\ 

 for NO.,, on the other hand. The invest igat ion of the variation of 

 the fluorescence of quinine sulphate, as well as the variation of the 

 rotation of the plane of polarisat ion of nicotine, gave in the hands of 

 (Mad-tone manv proofs of the entire applicabilit v of IJerthollet's 

 doctrine, and in particular demonstrated the influence of mass which 

 forms the chief distinctive feature of the, in his time, but little appre- 

 ciated teaching of liert hollet . 



