14 HOSTETTER AND SOSMANI MERCURY STILL 



designs for the furnace might be safely employed; such, for 

 instance, as winding the resistance wire on an asbestos-covered 

 metal tube. Having at hand, however, an alundum tube of 

 suitable size, we found it convenient to wind the wire directly 

 upon this tube, and to hold the wire in place with alundum 

 cement. The alundum tube has an inside diameter of 1^ inches 

 (38 mm.) and is 4| inches (114 mm.) long. The winding con- 

 sists of 51 turns (12 to the inch) of No. 30 nichrome wire (diam- 

 eter 0.010 inch, or 0.25 mm.), giving a total of approximately 

 24 feet (7.3 meters) of wire. Its resistance is about 160 ohms 

 cold and 200 ohms hot, and the current is about 0.6 ampere. 

 The furnace rests on a disk of heavy asbestos board and is 

 jacketed with ordinary asbestos-magnesia pipe covering. The 

 neck of the still is covered with loose asbestos fiber. 



Preliminary treatment of the mercury. As here constructed 

 this still is intended for the final distillation of mercury that has 

 been previously treated to remove the gross impurities. This 

 may be done (a) by the well-known process of Lothar Meyer* 

 since modified by Hildebrand^ and by Desha,* in which the 

 mercury is allowed to pass in a fine stream through a long column 

 of dilute nitric acid ; (b) by making the mercury the anode in n. 

 nitric acid bath and electrolyzing ;^ (c) by passing air through 

 the slightly heated mercury;^ (d) most thoroughly of all, by the 

 method of Hulett and Minchin,^ consisting in subjecting the 

 mercury to a preliminary distillation during which a stream of air 

 is bubbled through it. The first three methods have recently 

 been combined and developed into an automatic process.* 



Another very simple but surprisingly effective method of 

 removing impurities, which is not generally known and which 

 has been ascribed to Henry Leffman, is to shake up the con- 



2 Meyer, Lothar. Z. Anal. Ch. 2: 241. 1863. 



3 HiLDEBRAND, J. H. J. Am. Chem. Soc. 31 1 933-935. 1909. 



4 Desha, L. J. Am. Chem. J. 41 : 152. 1909. 



6 Wolff, F. A., and Waters, C. E. Bull. Bur. Standards 3: 624-625; 4: 9-11. 

 1907. 



« Crafts, J. M. Bull. Soc. Chim. Paris 49: 856. 1888. 



^Hulett, G. A., and Minchin, H. D. Phys. Rev. 21:388-398. 1905. 



•Patten, H. E., and Mains, G. H. J. Ind. Eng. Chem. 9: 600-603. 1917. 



