A F F

(

A F F

19 )

o5' a precise portion of oxygen in the oxyd sa-turated by a given quantity of sulphuric acid.

Iron, Sulphur and Oxygen.

We shall briefly mention these, on accountof an apparent anomaly in the relation betweenthe sulphuret and sulphat as already laid down.

Suhsulphuret of Iron. This was formed byheating red-hot for a considerable time a mix-ture of thin iron plate and thrice its weight ofsulphur, till all the excess of the latter wassublimed. The remaining sulphuret of irontyas brilliant, brittle* and magnetic only in pow-der. A given portion of it was analyzed bybeing first totally dissolved and acidified innitro-m.uriatic acid, and the sulphuric acid thusgenerated was separated by muriat of barytesand the oxyd of iron by ammonia. Reckoning31 per cent, of acid, or 13.797 of sulphur, insulphat of barytes, and 69.3 per cent, of iron inthe peroxyd here produced by the action of thenitro-muriatic acid, this suhsulphuret of ironwould consist nearly of

Sulphur . . 37 — 58.75

Metallic iron 63 — 100.00

100

158.75

The super-sulphuret of iron, or natural crys-tallized pyrites, gave by a similar analysis,Sulphur . 53.9 2 — 117

Iron . . 46.08 — 100

100.00

217

Therefore the sulphur combined with 100parts of iron is twice as much in the super-sulphuret as in the suhsulphuret.

Oxyds of Iron . This very important sub-ject has been examined herewith peculiar care.It was first asserted by Proust, and has beenpretty generally allowed, that there are buttwo oxyds of iron, the black and the red oxyd,the former being the suboxyd and the latter theperoxyd. That there are these two distinctoxyds is not doubted, but Thenard has givensome experiments which appear to establish

another oxyd of a still lower degree of oxy-genation than the black oxyd, and which whenfirst separated from its solution is nshite. Ifthis be correct, there are three oxyds, namely,the white, the black, and the red, of which thelatter has the highest proportion of oxygen.The existence of this white oxyd is also pro-bable on account of the ratio of oxygenation, aswill be further mentioned here, and also in thearticle Iron in this Appendix .

At present however only the black and thered oxyd are concerned, which may be heretermed the Suboxyd and the Peroxyd .

The composition of these ns determined byBerzelius from many experiments, is the follow-ing.

For the suboxyd

Iron . 77.22 — 100.0

Oxygen 22.78 29.5

100.00

For the peroxydIron . 69.31Oxygen 30.66

100.00

129.5

100.00

44.25

144.25

Therefore the oxygen of the peroxyd is to thatof the suboxyd only as 1 •§. to 1. for 29. 5 Xif— 44.25.

But on the other hand the sulphur of thesuper-sulphuret is twice the proportion of thatin the sub-sulphuret: and therefore if each ofthese sulphurets were acidified and convertedinto a sulphat of iron (the base of the sulphatcorresponding with the sub-sulphuret being thesuboxyd, and that of the other sulphat beingthe peroxyd) it is evident that the laws thatregulate this change as deduced from the sul-phuret and sulphat of lead could not be pre-served.

The combinations that would take place areas follows.

The sub-sulphuret converted into a sulphatedsuboxyd would give

Iron

Sulphur

100.00

58.75

with

Oxygen.

29.50

86.03

Subsulphurot 158.75 115.53

give 129.5 Suboxyd— 144.78 Sulphuric acid

274.28 Sulphated Suboxyd

In this case all the laws of combination areobserved pretty accurately, the sulphuric acidsaturating so much of the base as contains oxy-gen equal to half the sulphur in the acid,

within a trifling difference. But on the otherhand, if the supersulphuret of iron or thenatural crystallized pyrites (which contains adouble proportion of sulphur) were totallyc 2