MABERY. — SULPHUR PETROLEUMS. 11 



stopcock is fully open ; any adjustment is easily obtained, and the 

 manometer may be held stationary witliin one millimeter at any 

 desired point during several hours. 



In the distillation of small quantities of liquids requiring constant 

 attention, we have used a piece of glass tube forty-five to sixty milli- 

 meters long, attached to the side stopcock, with a sliding support near 

 the end. In vacuum distillations on a large scale it is more convenient 

 to refer to the entire length of the manometer column, since at any 

 time leaks may occur that are indicated only on the lower portion of 

 the graduated scale. Wiih a short manometer column alone, much 

 time may be lost in waiting for an exhaustion that is interfered with 

 by leaks. 



In heating the still, direct contact with the flame was prevented by 

 maintaining an air space above the burner by means of a sheet of 

 asbestos. With such application of heat equally on the sides and bot- 

 tom, there was less danger of decomposition at high temperatures. 

 All but the highest distillates were collected in a Warren hot con- 

 denser containing a glass worm. With this condenser vacuum distilla- 

 tions are easily controlled, and, as in distillations under atmospheric 

 pressure, with a great economy in time. Continuous distillation is 

 possible without losing the vacuum, by drawing in consecutive frac- 

 tions through the rear tubulure of the retort. The two receivers 

 shown in the figure are convenient, and some additional advantage 

 would be gained by means of an independent vacuum connection with 

 the lower receiver. Several supports are not represented in the 

 figure. Much time and tedious labor were expended on this apparatus 

 before all the difficulties were overcome ; but the compensation was 

 ample, since by means of it we have been able to separate in con- 

 siderable quantities constituents of high boiling points without decom- 

 position, which otherwise would have been impossible. As an evidence 

 of its usefulness, during several months continuous distillations were 

 in progress, in charge of assistants, with highly satisfactory results. 

 Distillates were collected at intervals of 10°, 5°, and 2°. The depres- 

 sion in boiling points by the diminished pressure in vacuum distillation 

 varies between 60° and 65° for the lower constituents, and 125° or 

 more for those collected between 300° and 350°. The residue above 

 350° (450°-500° atmospheric pressure) in both Ohio and Canada oils 

 had apparently undergone but little decomposition ; in appearance, it 

 was a thick, ready flowing oil, with scarcely any odor. 



A portion of the residual oil above 350° in vacuo was redistilled in 

 an ordinary boiling flask, and the temperatures of the vapor and of 



