PROCEEDINGS OF THE AMERICAN ACADEMY. 



On account of the large consumption of oxygen in burning rap- 

 idly a considerable weight of oil, — at least three times the quantity 

 theoretically required for oxidation, — and finding that the combus- 

 tion proceeds with equal facility in air, nearly all our determina- 

 tions have been made in a current of air supplied under pressure, 

 with the same means for exhaustion that Burton found advanta- 

 geous. The operation requires close attention and 0.5 to 1 gram 

 of oil may easily be burned in forty-five minutes to one hour, de- 

 pending upon the nature of the substance, the heavier oils especially 

 if containing much sulphur being the most difficult to burn. The 

 higher sulphides will not support a continuous flame, and dependence 

 must be placed upon a very hot tube ; with the naore volatile oils it is 

 sometimes difficult to maintain a continuous flame even in oxygen, the 

 combustion proceeding in long intermittent non-luminous flashes. If 

 the flame becomes luminous the rapidity of volatilization must be 

 instantly checked, and the flow of air increased. The appearance 

 of white fumes in the forward part of the combustion tube or the 

 absorption tube, indicating improper adjustment as to the temperature, 

 flow of gas, or rate of volatilization, is invariably attended with low 

 results. The completeness of the absorption in the U tube was tested 

 by placing a second tube beyond it containing a similar solution, but 

 no trace of acid was found in the second tube when the excess of 

 alkaline hydrate in the first at the end of the analysis was not less 

 than 15-20 c. c. With a smaller excess in rapid combustions there is 

 danger of loss. The oil for analysis is weighed in a bulb or tube of 

 hard glass, and it is sometimes convenient to transfer most of it to a 

 platinum or a porcelain boat, which may easily be accomplished with- 

 out loss within the combustion tube provided there is a gentle current 

 of air inward and the combustion tube in front has previously been 

 heated to the required temperature. 



In the examination of Ohio and Canadian sulphur petroleums for 

 identification of the paraffine, aromatic, and unsaturated hydrocarbons, 

 sulphur compounds, and other constituents, with which I am at present 

 engaged, numerous determinations of sulphur have been necessary, and 

 the extreme convenience of combustion in air has greatly facilitated 

 the separation of the various products. As an evidence of the reli- 

 ability of this method, the following results are selected with parallel 

 determinations by the Carius method : — 



