10 



Conductivity of Aqueous Solutions. Part II. 



not become completely full of liquid; and secondly, it furnishes a means 

 of measuring the specific volume of the solutions. The first provision is 

 necessary since the bomb is designed to withstand the vapor pressure, but 

 not the fluid pressure of the liquid. A knowledge of the specific volume 

 is required in order to calculate the equivalent from the observed conduct- 

 ance. A measurement of the resistance between L 2 and L 3 , together with 



a measurement of that between L l 

 and L 2 , when preceded by a calibra- 

 tion which may be made once for 

 all, shows, as will be explained 

 more fully in section 8, at any time 

 after the solution has expanded suf- 

 ficiently to come into contact with 

 the auxiliary electrode, just how 

 high the liquid stands, and therefore 

 how much vapor space remains. 



The small platinum tube T\ serves 

 to exhaust the air from the bomb. 

 The method of doing this will be 

 apparent from the diagram and the 

 following description. The hollow 

 screw K is connected by means of 

 rubber tubing with a Richards 

 water pump, and is at first raised so 

 that air can come out under the 

 little steel bicycle ball which rests 

 on the upper end of the platinum 

 tube. After the air is removed until 

 a pressure gauge shows a pressure 

 within of about 2 cm., and while the 

 pump is still in operation, the part 

 K is screwed down, thus forcing the 

 Fig i steel ball upon its seat and closing 



the end of the tube. 

 The solution comes into contact with nothing but platinum, quartz- 

 crystal, and gold, except at the top of the narrow tube, T ls where it may 

 touch the steel ball. The latter could be gold-plated ; but this has proved 

 unnecessary, since there is scarcely any circulation through the narrow 

 tube. 



The lower electrode, as well as the auxiliary electrode and its sur- 

 rounding tube, are well platinized. The body of the lining is not platin- 

 ized, since on account of its great surface this is not necessary. 



