12 



Conductivity of Aqueous Solutions. Part II. 



with a bottom piece welded in. Near the top two pieces of iron pipe C 

 about 2 cm. in diameter and 25 cm. long are screwed in, to serve as con- 

 densers. These condenser tubes are given a slight pitch, but their outer 

 ends should not be higher than the top of the heater. To increase their 

 efficiency, a loose roll of iron-wire gauze is put into each of them. The 

 top of the bath, which should be turned off square in the lathe, is covered 

 with a large watch-glass D, in which holes are drilled for the thermometer 

 T, and the lead-wires to the bomb. A tube of thin sheet iron Q, about 

 12 cm. in diameter, with a flange at the bottom, is placed in the heater 

 and held in the middle by projecting pins. Small holes are drilled through 

 this tube at the bottom, and two rows of large holes at the top. The func- 

 tion of this tube is to prevent the bottom of the bomb from getting hotter 



than the top; for, if it does this by ever so 

 little, a constant evaporation and condensa- 

 tion goes on in the bomb, which interferes 

 with the readings of the auxiliary electrode 

 and the specific-volume determinations. The 

 inverted mica cone N is put in for the same 

 purpose ; it prevents the cold condensed 

 vapor from dripping upon the top of the 

 bomb. These arrangements also protect the 

 bomb more effectually from radiation and 

 convection-currents from the walls of the 

 heater. The holes in the glass cover through 

 which the lead-wires and the thermometer 

 enter are but little larger than these, so as to 

 prevent loss of vapor. The thermometer is 

 supported by means of a cork stopper which 

 rests on the top of the watch-glass. The 

 insertion of cork stoppers in the holes is not 

 advisable, as they cause the hot liquid to escape through their pores. The 

 bomb is supported in the heater by means of a brass frame F , and suspen- 

 sion wires W , which hang on two steel pins screwed into the walls of the 

 heater. At the top of each of the two suspension wires is a loop, so that by 

 inserting a steel hook in each of these loops, the bomb is easily removed 

 from the bath while still hot. The sides of the heater are well jacketed 

 with asbestos. It is supported on a metal tripod by means of three steel 

 pins, which project through the asbestos covering. It is heated by gas- 

 burners below, one sufficing after the bomb and heater have become hot. 

 Commercial xylene was first used for the 140 bath, but the pure meta- 

 xylene was found to give a more constant temperature and one more 

 uniform in the upper and lower parts of the bomb. To prevent the escape 



Fig. 2. 



