IN STUDYING QUESTIONS OF CHEMICAL MECHANICS. 377 
if it were negative, this would indicate that some water must be 
removed from the mixture formed of the two solutions in order 
to obtain the constant relation desired, which, as it can only be 
effected by evaporation, would involve chances of inaccuracy, 
independently of the tediousness of the process. This inconveni- 
ence is ayoided by employing tartaric acid in the solid state ; for 
then, e’ being null, <’ equal to 1, and the given multiple v an in- 
teger or fractional number always positive, we can always assume 
the weight T great enough that the product m T may surpass 
or equal e’ B. But, besides the time which complete liquefaction 
of the mixed system would require, we should always have to 
apprehend that it was not sufficiently charged or stable; and it 
is far more advantageous to have only te mix solutions already 
made. Fortunately the expression of E shows, that to be able 
to operate thus, it suffices to employ a tartaric solution suffi- 
ciently charged with acid for the factor n/—e' to be positive. 
In fact, this being supposed, when a known weight T of this 
solution has been placed in a counterpoised phial, on the scale of 
the balance, we have only to add gradually weights B of the 
boracic solution, such that E may remain positive or become 
exactly null, according to its expression, which would leave only 
to dilute the system by this quantity of water E, to give it the 
proportions required by the relation ». And if this limit at 
which E is positive has been accidentally exceeded, from too 
much B of the boracic solution having been added, the equili- 
brium may always be re-established by a further small addition 
of the tartaric acid T. Now, the previous condition of n¢ — ée 
positive is very easy of fulfilment; for, designating by n/ the 
ponderable relation of water to the tartaric acid, in accordance 
with which this solution is made, there will result 
and as we always have 
did= i 
we deduce from these two equations, 
Tt tea ees 
al er P 1? 
which gives 
VOL. IV. PART XV. QE 
