[seyerI OILINESS of HYDROCARBONS 71 



Thus the coefficient of friction of an unsaturated oil ha\-ing the 



Xi_K2 



same viscosity as the saturated would be r;^ — tt 



A2 ri-i 



or 0.0076, which is almost twice that of the other. 



It was noticed that the unsaturated oil, after having gone through 

 the machine once, had become turbid and upon standing a considerable 

 sediment of carbon was obtained. The saturated oil, on the other 

 hand, showed no deposit of carbon. The decomposition of the former 

 must have been due entirely to the pressure as the temperature never 

 rose above 35°C. 



The above results indicate that the coefficient of friction is not 

 independent of the chemical nature of the oil. Ubbelohe,^ on the 

 other hand, has shown experimentally that under the same mechanical 

 conditions, oils with the same specific viscosity have the same co- 

 efficient of friction. His results are probably due to the fact that 

 the oils which he used were similar in chemical composition, for it is 

 obvious that one may have many liquids with the same viscosity as 

 lubricating oils yet have a very high coefficient of friction. 



VK* 



In the derivation of the above formula, X = — r; two assumptions 



are made, one that V varies directly as K. This has been shown by 

 Lacsher to be correct between certain limits. The second is that Y, 

 the thickness of the film, is always constant and that, therefore, there 

 is always a perfect oil film formed. The results obtained in this 

 experiment would seem to show that oils differ in their film forming 

 properties, the unsaturated oil forming a better one than the saturated, 

 thereby reducing the friction. Another fact which proves that the 

 oil film is never perfect is that journals and bearings do wear out. 

 Thus to make the above formula agree more closely with the facts 

 some correcting factor should be introduced expressing the film 

 forming properties or chemical nature of the oil. In the hopes of 

 determining the nature of this factor the investigation of the relative 

 film forming or lubricating properties of the various series of hydro- 

 carbons is being undertaken. 

 Chemical Laboratory, 



University of British Columbia, 

 Vancouver, B.C. 



iPetrol, 7, 773, 882, 938. (1912.) 

 * Where V, P, and Y are constant. 



