MABERY. — SULPHUR PETEOLEUMS. 27 



toward bromine and the nature of the decompositions by cracking 

 will receive furtlier attention. 



The portions distilling below 150° were next submitted to pro- 

 longed fractional separations under atmospheric pressure with the aid 

 of Hempel columns and Warren condensers. We were led to appre- 

 ciate the exhaustive labors of our predecessors in their investigations 

 on petroleum, and our indebtedness to them for the efficient means at 

 present available for conducting such distillations. For the separation 

 of complex mixtures, especially in considerable quantities, in point of 

 efficiency the Warren condenser leaves nothing to be desired. It 

 appears to effect a more rapid separation than the Hempel column, 

 although the latter is of great service. The Hempel method has the 

 advantage that it requires less attention, with no loss of time in heat- 

 ing a bath nor in maintaining a constant temperature in the bath. 

 From the description of Warren's hot condenser given in the 

 treatise on Chemistry, Vol. III. Part 1, by Roscoe and Schorlem- 

 mer, an erroneous im[)ression must have been received concerning this 

 apparatus. On pp. 149, 150, the following words appear: " An appa- 

 ratus has been employed by AVarren in the fractional distillation of 

 tar oils and petroKums. This permits a complete control over the 

 temperature of the vapor, accomplished by an air bath round which a 

 spiral tube is placed, connected with the boiling flask. The tempera- 

 ture of this air bath is regulated by a lamp. The licjuid used for 

 heating the air bath may be either water, oil, or fusible metal, and into 

 this the thermometer is placed. ... In distilling petroleum the differ- 

 ence in temperature between the boiling liquid and the air bath was, 

 to begin with, about 35°, or even more." The idea conveyed here is 

 that the constant temperature is maintained by means of an air bath, 

 although it is evident from the following description, taken from the 

 original memoir,* that there is not the remotest allusion to an air 

 bath : " In the new process, perfect control of the temperature of the 

 vapors is secured by simply conducting these vapors upwards throtigh 

 a worm contained in a bath the temperature of which is regulated by 

 means of a lamp, or by a safety furnace. The bath may be of oil or 

 water or metal for very high temperatures, as the case may require, 

 and it is furnished with a thermometer. That this bath may be 

 equally adapted for the separation of liqt;ids boiling below the com- 

 mon temperature, an empty vessel is permanently secured in the 

 interior of the bath by means of straps of metal across the top, to 



* Mem. Amer. Acad. (N. S.), IX. 125. 



