On the supposition that metals combine with charcoal, the appropriate names for the compounds would be _carburets_ of the respective metals. This combination, if it exist at all, seems very rare, that with iron being the only one generally acknowledged. No combinations of carbone with the earths and alkalies, have, as far as I know, been noticed; and those with the elements oxygen, hydrogen, sulphur and phosphorus have been described in the former volume. Since that was printed an ingenious experimental essay on the “_Sulphuret of carbon_ or alcohol of sulphur,” has been published by Berzelius and Dr. Marcet. Some account of this compound, under the name _carburetted sulphur_, has been given (VOL. 1. page 462); but the additional information is of sufficient importance to require notice here. The pure liquid is of sp. gr. 1.272; and the elasticity of its vapour at 66° is equal to 10.76 inches. It burns with a blue flame and sulphureous odour, without sensibly depositing water on cold glass exposed to the fumes. It has an acrid, pungent taste, and a nauseous smell, differing from sulphuretted hydrogen. By various experiments it was found to consist of sulphur and carbone in the ratio of 85 to 15 nearly; that is, 2 atoms of sulphur to 1 of carbone. From other experiments it did not appear to contain any hydrogen. From some experiments I made in June 1818, on the combustion of the vapour of carburet of sulphur in oxygen gas, I was led to suspect at least, that an atom of hydrogen attaches to the two of sulphur and one of carbone in its constitution. But not having an opportunity to pursue the subject, I merely make the observation for future experience to determine upon the question. 1. _Carburets of iron._ There are three distinct substances which are now commonly believed to be constituted of carbone and iron, known by the names of _Plumbago_, or black lead, _Cast Iron_ and _Steel_. Plumbago is a natural production, found in greatest perfection in the Borrowdale mine, near Keswick, Cumberland. It is chiefly used in making pencils.--It seems to be constituted of carbone and iron by the concurrent experience of all who have examined it: but the proportions are not uniform, some having found 10 and others only 5 per cent. of iron in it. From this circumstance it would seem doubtful whether iron is an essential element. As carbone is known to be exhibited in various forms of aggregation, it is not improbable that plumbago may be one of those forms; it is evidently not a mere mixture of common charcoal and iron, or its oxide.