The properties of caoutchouc clearly show, however, that its actual molecular structure is considerably more complex than is represented by the empirical formula, and that it is to be regarded as the polymer of a terpene or similar hydrocarbon and composed of a cluster of at least ten or twenty molecules of the formula C5H8.
Since the heat of combustion of a hydrocarbon is equal to the heat of combustion of the carbon and hydrogen it contains minus its heat of formation, those hydrocarbons with positive heat of formation generate less heat on burning than the elements from which they were formed, whilst those with a negative heat of formation generate more.
Consider now the combustion of a hydrocarbon of the general formula CH 2m.
It is convenient to distinguish between aliphatic and aromatic acids; the first named being derived from open-chain hydrocarbons, the second from ringed hydrocarbon nuclei.
Deferring the detailed discussion of cyclic or ringed hydrocarbons, a correlation of the various types or classes of compounds which may be derived from hydrocarbon nuclei will now be given.
Dewar and Jones suggest that in the latter reaction it is the metallic nickel which is probably the reducing agent effecting the change, since it is only dissolved in any quantity when the anthracene hydrocarbon is produced.
Numerous hydrides are known; heated with red phosphorus and hydriodic acid the hydrocarbon yields mixtures of hydrides of composition C10H10 to C10H20.
Hantzsch, Ber., This assumption also shows the relationship of the diazonium hydroxides to other quaternary ammonium compounds, for most of the quaternary ammonium hydroxides (except such as have the nitrogen atom attached to four saturated hydrocarbon radicals) are unstable, and readily pass over into compounds in which the hydroxyl group is no longer attached to the amine nitrogen; thus the syn-diazo hydroxides are to be regarded as pseudo-diazonium derivatives.
Mixing the coal gas with water gas, which has been highly carburetted by passing it with the vapours of various hydrocarbons through superheaters in order to give permanency to the hydrocarbon gases.
The relation between the heat of combustion of a hydrocarbon and its heat of formation may be readily seen from the following example.