viii THERMO-ELECTRIC CRYOSCOPY 159 



The two test-tubes, each about 1 cm. in diameter, are 

 supported in a perforated cork bung (c), which fits 

 loosely in an outer large test-tube, which in turn is im- 

 mersed in the freezing-bath, and forms the freezing- 

 chamber (/). The perforated bung is held about the 

 middle of the large test-tube by a metal rod (m) a piece 

 of stout brass wire fixed into it and passing through 

 another bung which closes the mouth of the outer test 

 tube. The rod is prolonged above the second bung (d), 

 and forms a handle by which both bungs may be removed 

 simultaneously from the freezing-chamber carrying the 

 small test-tubes in the lower bung. 



The cork connecting-piece (s) carrying the eureka wire 

 of the couple is furnished with a wide median vertical 

 perforation parallel to the two pine rods. When the pine 

 supports are placed in the small test-tubes, the metal rod 

 is passed through the perforation in the connecting-piece 

 and works loosely in it. Before fixing in the connecting - 

 piece the pine supports are thoroughly impregnated with 

 paraffin-wax by keeping them submerged for some time 

 in melted wax near its boiling-point. The junctions and 

 the wires coming from them are laid along the supporting 

 rods thus prepared and fixed in the connecting-piece, and 

 are bound to the rods, and the whole is waterproofed and 

 insulated with several coats of collodion varnish. The 

 supporting rods are continued above the connecting-piece 

 and are produced through corresponding perforations in 

 the upper bung (d), in which they fit loosely. It is 

 convenient that some kind of easily detached stop (q) 

 should be fixed on one of the rods above the upper bung 

 to prevent the rods slipping out of this bung when the 

 test-tubes are removed. The copper leads (I) emerge 

 from the freezing-chamber along one of the supporting 

 rods. 



This arrangement, which will be easily understood by 

 reference to Fig. 25, allows the junctions in each of the 



