THE ACTION OF CHEMICAL AFFINITY. 
221 
IV. An alteration in the mass of any one of the binary compounds present alters 
the amount of every one of the other binary compounds, and that in a regularly pro- 
gressive ratio ; sudden transitions only occurring where a substance is present which 
is capable of combining with another in more than one proportion. 
V. This equilibrium of affinities arranges itself in most cases in an inappreciably 
short space of time, but in certain instances the elements do not attain their final 
state of combination for hours, or even days. 
VI. The phenomena that present themselves where precipitation, volatilization, 
crystallization, and perhaps other actions occur, are of an opposite character, simply 
because one of the substances is thus removed from the field of action, and the equi- 
librium that was first established is thus destroyed. 
VII. There is consequently a fundamental error in all attempts to determine the 
relative strength of affinity by precipitation ; in all methods of quantitative analysis 
founded on the colour of a solution in which colourless salts are also present ; and 
in all conclusions as to what compounds exist in a solution drawn from such empi- 
rical rules as that “ the strongest base combines with the strongest acid.” 
NOTES ADDED AFTER THE PAPER HAD BEEN READ. 
Note A. 
That two or more solutions of the same salt in the same solvent and of etjual depth 
of colour are of the same strength, requires no proof. Hence I apprehend no objec- 
tion can be raised against the conclusion, that the gross arnounts of salt dissolved in 
the different solutions are directly proportional to their volume. But it may be 
objected, that though this is true of the solutions when diluted to an equality of 
colour, it is not necessarily true of the solutions before they were diluted, for the 
solvent may exercise some chemical action on the coloured salt, absolutely increasing 
or diminishing its quantity. Should such be the case, it appears to me actually the 
most correct plan of proceeding to reckon the result when the solutions of the 
coloured salt are of equal strength, that is to say, when the solvent is in each case in 
the same proportion to the dissolved salt ; for the disturbing influence of the solvent 
is thus practically got rid of, by its reduction to an equality in all the solutions com- 
pared. 
There is however a more serious objection, namely, that the solvent may act dif- 
ferently on the coloured salt, according to the nature or the quantity of the colour- 
less salts present at the same time in the several solutions, or that these salts may 
act differently according to the amount of solvent with which they are conjoined. 
That this may be the case to a slight extent is very possible, but the experiment 
recorded on page 202, shows that it was too inconsiderable to be appreciated in 
the cases there submitted to examination. As this is an important matter, I have 
2 H 2 
