4 PROCEEDINGS OF THE AMERICAN ACADEMY. 



ture at the level of the lower tubes is about 9° higher. For tem- 

 peratures higher than 275° a second heating tube is necessary. 



It is frequently convenient to be able to regulate within close limits 

 the flow of gas for the required temperature without further attention 

 after lighting tlie jets. The device shown in Figure 2, which sug- 

 gested itself for tliis purpose, consists in attaching to the end of the 

 gas valve by means of a screw thread a brass cap with an index of 

 stout copper wire moving in front of a graduated circle with a radius 

 of about six inches. 



With glass tubes of large size, — those we use are l.o mm. inside 

 diameter, — well sealed and with strict adherence to certain conditions 

 which have elsewhere been described by A. W. Smith and me,* there 



is little danger of an explosion. The 

 quantity of nitric acid should not be 

 in excess of twenty times the weight 

 of the substance taken, and after heat- 

 ing to 175° for fifteen hours the tubes 

 are opened, — best without remov- 



^ ing from the furnace, — resealed and 



Fig. 2. . ' . 



heated aofain to 250 during five to 



ten hours. The serious objection to the Carius method for sulphur is 

 the slow process of oxidation, and it seems hardly possible to hasten 

 the operation by raising the temperature, since glass tubes will not 

 stand the great pressure. 



In studying various methods depending upon the oxidation of sul- 

 phur by combustion I have found that nothing less than complete 

 oxidation gives reliable results. Many experiments on fractional 

 combustion have shown clearly that compounds with high percentages 

 of sulphur do not yield concordant results, even when the sulphur 

 compound is diluted with a sulphur-free oil. I have found Burton's 

 adaptation of the Sauer method reliable and expeditious, and with 

 certain modifications presently to be described it is perfectly satisfac- 

 tory for the analysis of oils of high as well as low percentages of 

 sulphur. In Figure 3 the inlet tube for oxygen or air is shown as enter- 

 ing through the rear stopper, as proposed by Mixter, and extending 

 just to the centre of the constriction. In the combustion of some of 

 the oils which we have under examination, the temperature must be 

 maintained as high as the most infusible Bohemian glass will stand, 

 and at such temperatures the smaller tube within is distorted if it is 



* Amer. Chem. Journ., XVI. 83 



