On definite Proportions. 95 
they lose no more water during ignition. The nitrate of potass 
gives off in the operation oxygen gas, nitrous acid, and lastly 
nitrous gas, but does not afford a drop of liquid acid. The tar- 
trate of potass, precipitated with nitrate of the protoxide of lead, 
afferded, for 100 parts of the well dried salt, 155-7 of tartrate 
of the protoxide of lead. Consequently, according to the ana- 
lysis of this salt lately related, the tartrate of potass consists of 
Tartaric acid.. 58°69 100-0 
Potasss...... 41°31 70-4 
Now 70:4 parts of potass contain 11:93 of oxygen, that is, 
with a very slight difference, the same quantity as the protoxide 
of lead that saturates 100 parts of the acid. The slight difference 
may depend on the unavoidable loss of a small quantity of tar- 
trate of leid in the experiment. Hence it is evident, that the 
' tartrate of potass can contain no water of crystallization. 
The supertartrate of potass, on the contrary, or the crystals 
of tartar, contains water of crystallization, which cannot be ex- 
pelled by heat. The salt employed for the preceding experiment 
had been made of pure tartaric acid with pure carbonate of po- 
tass, and was therefore perfectly free from lime. I precipitated 
the remaining portion of it with tartaric acid, I dried very care- 
fully the powdered precipitate, and bumt 10 grammes of it in a 
platina crucible. The coaly alkaline mass was carefully washed 
with muriatic acid,the muriatic solution dried, and the salt ignited. 
1 obtained in one experiment 3°91, and in another 3-915 gr. of 
muriate of potass. I found by another experiment, as Wollaston 
had already observed with respect to the oxalic acid, that the re- 
siduum of 10 gr. of supertartrate of potass, after ignition, was 
sufficient to saturate 10 gr. of the supersalt: so that the potass 
must be combined with twice as much acid in the supersalt as in 
the neutral salt. But the muriate, which was obtained, answers 
precisely to 24-8 per cent. of pure potass, which must conse- 
quently form the superacetate with 70°45 of tartaric acid, and 
the remaining 4°75 parts must be water. Hence the superacetate 
of potass consists of 
Tartaric acid.. 70°45 
Potass....... 24°80 
Water nid. s.<, A479 
This quantity of potass contains 4-206, and the water 4-192 
parts of oxygen; consequently the water of crystallization in 
this salt contains exactly as much oxygen asthe base. But since 
this water can only be expelled by the addition of a second base, 
and is exactly the same quantity as would have been combined 
with the excess of acid in a separate form of crystallization, this 
salt may be considered as a double salt, of which water is the 
second hase, 
Salts 
