176 PROCEEDINGS OP THE AMERICAN ACADEMY. 



total percentages of carbon and hydrogen in most instances have ap- 

 proached 100 per cent to within the limit of the error of analysis, althoagh 

 it is true that these distillates were subjected to close fractional distillation 

 wiihiu 1°, while those of MarkownikofF and Oglobine were distilled only 

 a few times within limits of 5°. In all the distillations of Pennsylvania, 

 Ohio, and Canadian petroleum, a slight coloration of the still residue 

 after a long series has been observed, which may be due to a small amount 

 of oxygen compounds. 



On standing with metallic sodium, all the unpurified distillates described 

 in this paper deposit flocculent precipitates, more or less colored, which 

 are evidently products of decomposition. This cannot be due to the 

 action on the principal hydrocarbon, since when purified such action 

 by sodium is not observed. Neither should the aromatic hydrocarbons 

 behave in this manner toward sodium. Tiiese precipitates must be 

 formed from the oxygen or the nitrogen compounds in the oils, probably 

 from the former. They cannot be due to decomposition of sulphur com- 

 pounds, since Pennsylvania oil contains only a very small percentage of 

 sulphur, and the other distillates were all treated with alcoholic mercuric 

 chloride. It is quite probable that ordinary sulphuric acid combines to a 

 certain extent with some of the aromatic hydrocarbons. A more extended 

 study of the action of sulphuric acid on a larger scale as in refining, would 

 doubtless be interesting and profitable. 



Concerning the action of fuming sulphuric acid, no further explanation 

 is necessary than has been given in connection with the experiments which 

 describe its behavior toward these petroleum distillates. 



So far as possible, all details of this work have been carried on under 

 my immediate and constant personal supervision. For efficient aid I am 

 indebted to the following gentlemen : Messrs C. A. Soch, private assist- 

 ant, 1894-95 ; E. Davidson, private assistant, 1895-96 ; E. J. Hudson, 

 molecular weight determinations, and other aid mainly in connection with 

 the chlorine derivatives of the hydrocarbons; W. F. Priebe, who selected 

 a portion of the work on the Pennsylvania distillates as the subject of a 

 thesis for the degree of Bachelor of Science ; and Messrs Giessen, Wat- 

 son, Worstall, Piwonka, Shaw, and AValker, for faithful assistance in the 

 routine work of distillation and combustions. 



The work now in progress includes a study of the pentanes, hexanes, 

 and heptanes in Pennsylvania petroleum, and the composition of the por- 

 tions of Pennsylvania, Ohio, Canadian, Berea Grit, and South American 

 petroleums between 216° and 350°. 



