On definite Proportions. 93 
whieh I attribute to some carbon contained in the iron, which 
was mixed with the hydrate. This quantity of oxide contains 
26°12 parts of oxygen, and the water combined with it 13 parts. 
Consequently in this experiment the oxide contained twice as 
much oxygen as the water. 
But in order that this proportion might have more than a single 
experiment for its support, I took some iron whieh contained 
less carbon, choosing for this purpose some harpsichord wire, 
n. 10; I suffered it to be oxidated in pure water, which was daily 
changed, in contact with a plate of platina, which accelerated the 
oxidation. After some weeks, I had again coliected enough for 
examination. This hydrate, dried for several days in the sun- 
shine, had a very light orange yellow colour, and left after igni- 
tion a fine red oxide, not at all magnetic, which amounted to 
§5°5 per cent. Consequently in this experiment the hydrate 
had contained 14-5 per cent. of water, which confirms the pre- 
ceding experiment ; and we see that the hydrate of iron, which 
forms on iron in water, contains a quantity of water of which 
-the oxygen is equal to Aalf-that of the oxide. It is however 
probable, as well from Mr. Liedbeck’s experiments, as from 
others which will hereafter be mentioned, that the oxide of iron, 
when in combination with other substances, is capable of taking 
up a quantity of water, of which the oxygen is equal to that of 
the oxide. 
5. Oxide of Tin. 
Ten grammes of pure tinfoil were oxidated in a glass flask by 
means of pure nitric acid; the fluid was evaporated, and the 
oxide ignited in the flask. It was of a light straw colour, and 
weighed 12-72 gr. In another experiment I obtained only12-71 er. 
According to the former experiment, the oxide of tin consists of 
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It is a known fact that oxide of tin, prepared with nitric acid, 
reddens litmus paper, but not after ignition. I thought at first 
that this might depend on some nitric acid adhering to it; but 
when the water, with which it was washed, uo longer reddened 
the paper, the oxide still possessed the property. It was only 
deprived of it by pouring on it & little ammonia; but the oxide 
now afforded, when ignited, water strongly impregnated with 
ammonia. ‘The oxide of tin therefore has as much right to the 
denomination of an acid as the tungstic acid, and the columbic 
acid, or rather the ‘* tantalic” oxide. : 
I dried some oxide of tin, which had been well washed, hut 
not treated with ammonia, in a sand heat. It lost by ignition 
6°6 per cent, After some hours, when the sand-bath was con- 
ir siderably 
