; On definite Proportions. 9} 
4. Oxide of Iron. 
The experiments of Mr. Liedbeck have for some time made it 
known in Sweden, that the yellow or brownish ore of iron called 
Meadow ore, ‘ Rasenerz,” contains the oxide in the form of a 
hydrate. My friend Mr. Tae eine of Cassel [now Professor 
of Technology at Gottingen, G.] wrote to me some months since 
that he had made the same eee, and kad found from 19 to 
21 per cent. of water in this hydrate, but considered the former 
number as the more correct. In this case the water would con- 
tain a quantity of oxygen amounting to two-thirds of that of the 
oxide of iron, or the water would contain as much oxygen as had 
been required for converting the given quantity of iron into a 
protoxide. Although this does not agree with the laws which 
have been laid down, it is evident that this latter view of the 
subject may lead to very instructive consequences ; and I was 
induced by it to add to these investigations the examination of 
the hydrate of the oxide of iron. 
Mr. Liedbeck had found, in the ores which he examined, 
20-8, 21-1, or 25 per cent. of volatile substances, of which water 
eoustituted about 20. Together with the oxide of iron, he found 
mechanical mixtures of sand, clay, silica, and so forth, which 
being deducted from the oxide, left from 60 to 62 per cent. only: 
and this portion of pure oxide contains as much oxygen as the 
water combined with it. 
I now examined some foreign specimens of this ore, and found 
in it 14:4, 13-1, 11-6, ... per cent. of water, accordingly as the 
ore was dried in the sun, or in a sand heat. The ore was not 
magnetic before ignition, but became more or less so after igni- 
tion. Hence it must have contained a little combustible matter, 
which must have increased the loss by ignition. When the oxide 
was dissolved, after ignition, in muriatic acid, it left behind a 
little silica, swollen up into a semi-gelatinous form, which conse- 
quently appeared to have been chemically united with the oxide. 
But the admixture of foreign substances was such as to render it 
impossible to determine the composition of this triple combina- 
tion of water, silica, and oxide of iron, with so much precision, 
that the result might be of the least utility as a basis for caleu- 
Jation. 
I now examined the yellow mass which is formed on weather- 
ing pyrites, and which I had often found to be free from sulphuric 
acid. ‘The specimen taken from one piece lost during ignition 
17°5 per cent.; from another 12 only. Both contained silica, 
and the first I afterwards found to exhibit traces of copper. 
I then prepared some hydrates of iron, by decomposing the 
sulphate, the nitrate, and the muriate of the oxide, with caustic 
ammonia, 
