540 PROCEEDINGS OF THE AMERICAN ACADEMY. 



Methyldichloracetate 0.3202 



Ethyldichloracetate 0.33S4 



Propyldichloracetate 0.3506 



In general, the data on specific heats of organic compounds are meagre 

 and not concordant. F'or the same substance the results of different 

 observers seldom agree in the third decimal place ; thej often do not 

 agree in the second, and even in the jSrst place (see tables of Landolt 

 and Bornstein). These variations are probably due to the fact that spe- 

 cific heat is materially affected by impurities in the substance, and the 

 temperatiires at which it is taken. Then, furthermore, the details of the 

 determinations demand very careful attention to insure concordant results. 

 In the determinations of the hydrocarbons to be described in this paper, 

 it was found that impurities depressed the specific heats very considerably. 



Although the paraffine series of hydrocarbons offers the best field for 

 study of an homologous series, very little has been done in the direction 

 of ascertaining the specific heats of these bodies. In a study of distillates 

 separated from Pennsylvania petroleum, by Bartoli and Stracciati,* the 

 specific heats of the following hydrocarbons were determined : 



The inference derived from these results was that the specific heats of 

 these hydrocarbons were remarkably constant. 



No data could be found relating to the specific heats of the methylene 

 hydrocarbons CnHsu, nor those of tlie series still poorer in hydrogen. With 

 the greatly extended uses of crude petroleum and refined distillates for 

 fuel, in gasoline and oil engines, accurate information concerning specific 

 heat and heat of vaporization is gi'eatly desired. 



Having in hand a great variety of hydrocarbons of the various series, 

 which have been prepared in as pure form as possible, and numerous 

 inquiries having been received for more complete information concerning 

 these physical properties, it seemed advisable to make some determin- 

 ations of these constants. 



The hydrocarbons of the series CnHj^+s? were obtained from Pennsyl- 

 vania petroleum, those of the other series from California petroleum. 



* Gazz. Chim., 1885, 417-445. 



