MABERY. COMPOSITION OF PETROLEUM. 257 



This collection of specimens seemed to offer a fair average of the oils 

 from the California fields, representing four different counties, and deposits 

 that yield oil in considerable quantities. 



Since these crude oils differed essentially in their appearance and in 

 their physical properties, in ascertaining their composition it seemed 

 advisable to examine them individually. 



In the spring of 1897 an examination of the Ventura oil was begun,* 

 and besides giving the composition of the crude oil. the fractional sepa- 

 rations were carried far enough in vacuo to identify the principal constit- 

 uents boiling below 175°. The several hydrocarbons homologous with 

 benzol, which have been found in petroleum from other sources, were 

 found to constitute a large part of the unpurified distillates ; but the 

 chief constituents were shown by their composition and specific gravity 

 to be metiiylenes, for the first time recognized as essential constituents of 

 American petroleum. 



Petroleum from Fresno County. 



A brief account of the composition of a specimen of crude oil from 

 Fresno County was given in the preliminary paper referred to above. 

 When this oil was subjected to distillation, it was evident that decompo- 

 sition could only be prevented in the fractions above 150° by collecting 

 them in vacuo. The portion collected below 150° atmospheric pressure 

 — 2090 grms. — was submitted to long continued fractional separation 

 within 1° until 50 grms. collected below 55°, and only 5 grms. between 

 55° and 68°. At 68°-70° the distillates amounted to 60 grms., which 

 was separated for the most part at 68°. The specific gravity of the 

 crude distillate at 68° was found to be 0.6913, and after thorough agita- 

 tion with fuming sulphuric acid, 0.6844. A combustion of the purified 

 oil gave the following percentages of carbon and hydrogen : — 



0.1692 grm. of the oil gave 0.5234 grm. COo and 0.2314 grm. HoO. 



The loss in this analysis is doubtless due to an escape of a very small 

 amount of gaseous decomposition products without complete combustion. 

 Combustion of such a volatile oil requires the closest attention in nianip- 



* Am. Chem. Journ., XIX. 790 (1897). 



VOL. XXXVI. — 17 



