338 Researches on Salts. 
It is generally thought that the number of subsalts formed by 
the same te wi and the same base, is much greater than that of the 
correspond rsalts or acid salts. So that five or six subnitrates 
of lead are aeeetiel, five or six subsulphates of copper, three or 
four subacetates of copper, etc., and the most irregular relations 
are considered as occurring in the composition of these bodies. 
My experiments do not give the same results. Whenever I 
have been able to obtain a crystallized subsalt, or it has been pos- 
sible for me so to control circumstances as to avoid a mixture, the 
composition of the product was exceedingly simple. I have thus 
been able to satisfy myself that there does not exist but a single 
subsalt, or at most but two, for the same acid and the same base. 
There is one fact whose importance is not perceived at first 
sight, but which must nevertheless be borne in mind to prevent 
errors; it is the influence of masses in the double decomposition 
of salts. It is not a matter of indifference, when one solution is 
to be ue by another, whether we pour the first liquid 
into the second or the second into the first. It is stated, for ex- 
am Be le , - an the oer that potash if added to a solution of sul- 
pha opper precipitates the hydrate from it. The truth of 
the ae is this; if potash is added drop by drop to the salt of 
opper in such a way as to keep this latter in excess, we obtain 
n sub-sulphate of constant composition ; by operating in an 
‘inverse manner, we produce the blue hydrate perfectly pure. With- 
ms the precaution of always maintaining in excess the liquid into 
position, when in reality they are only mixture 
nother not less striking example of this a diupavs of masses, % 
bc 
[ have noticed in the case of phosphate of soda and nitrate of lead. 
Bins phosphate of sa, PO: (Nee 2 05, 2Na? O, H? O 
a f N? 0* (Pb? H)=N? 05, 2Pb? O,H* O 
rs aPb: O, H?0 
PL 0+ (Pb: H)= SP 0" 2Pb? 0, H? O 
