58 SECTIONAL ADDRESSES. 



crude oil, but it is certain that others are formed during the distillatiou 

 process. It is clear that much opportunity for research work offers itself 

 here, and it is probable that small alterations in the method of distillation 

 may cause deep-seated changes in the character of the distillate, causing 

 it to be of greater service for particular purposes. The occurrence of 

 hydrocarbons of the naphthalene series in petroleum products has also 

 been clearly established. The higher fractions which constitute the 

 valuable lubricating oils also need attention, for it is now certain that 

 viscosity bears no relation to oiliness, that is, the capacity for acting as 

 an efficient lubricator. The addition of small quantities of ' polar ' 

 substances of the type of fatty oils or acids confers increased oiliness on 

 these compounds, and although we are now gradually reaching a stage 

 when we know more about the effects of such ingredients, the field for 

 research is still a large and important one. 



The formation of free carbon occurs during both the distillation and 

 ' cracking ' processes, in some cases to a very considerable extent. The 

 utilisation of this carbon for the purposes of making electrodes is an 

 important part of the industry, and the formation of carbon in a condition 

 in which it can be used by the rubber-tyre manufacturers is also likely 

 to become practicable as an outcome of the thermal decomposition of 

 hydrocarbons. 



At present we know nothing about the structure of the hydrocarbons 

 present in the lubricating oils. Indeed, it seems possible that these may 

 net be long-chain hydrocarbons with which the organic chemist is familiar, 

 but rather polymerised products formed from unsaturated components 

 liable to be formed or destroyed under comparatively mild conditions. 

 The relative ease with which the oil in the engine sump of a motor-car 

 loses its oiliness through continued use is not characteristic of the stability 

 usually associated with an organic hydrocarbon. Recent researches on 

 the formation of dimeric products of the simple type 



XCH=CHY XCH-CHY XCH-CHY 



-^1 I or I I 



XCH=CHY XCH-CHY YCH-CHX 



show that the ease of formation and stability of such systems depend on 

 the composition of X and Y. In some cases stable complexes of this 

 kind are formed which can be distilled without undergoing disruption, but 

 which are broken down slowly on prolonged heating even at a moderate 

 temperature. 



In the complex hydrocarbons under discussion the letters X and Y 

 represent hydrocarbon residues, probably themselves containing other 

 unsaturated linkages, and under the conditions of high pressure which 

 were probably present during the formation of natural petroleum it is 

 possible many of these four-membered rings are formed in a single 

 molecule, for example : 



XHC - CH - CH2 - CH - CHX 



II II 



YHC-CH-CH2-CH-CHY 



an expression which, incidentally, indicates the manner in which the 

 cyclohexane complex can also be produced by a similar process. So far 



