Heats of Vaporization of different Liquids, 27 



Conclusions. 



1. The form of electrolytic cell described is very suitable 

 for determining the specific conductivity of electrolytes 

 directly without reference to the physical properties of any 

 second electrolyte. 



2. The method of measuring the conductivity of electrolytes 

 described in this paper is, in our opinion, more convenient and 

 more accurate than the method in which alternating currents 

 are used. 



The Yorkshire College, Leeds, 

 June 1896. 



0' 



A 



IV. On the Heats of Vaporization of Liquids at their 

 Boiling -Points. By Miss Dorothy Marshall, B.Sc, 

 University College, London*. 



§ 1. rpHE work which is the subject of this paper is a con- 

 JL tinuation of that described in a previous paper by 

 Prof. Kamsay and the author (Phil. Mag. January 1896), and 

 was carried out in a similar manner. A full account of the 

 apparatus and method of experiment was given in the pre- 

 vious paper. 



§ 2. Two modifications only have been introduced, viz. : — 

 (i.) The current which is to make the liquids boil is allowed 

 to run through the other resistances of the circuit for at least 

 ten minutes before the beginning of the experiment proper, in 

 order that their temperatures may be already steady at the 

 moment of starting. By adopting this simple precaution the 

 current strength was constant from the first, and the points 

 of balance on the bridge-wire were much steadier and more 

 easily found than they had been in earlier experiments. 



(ii.) Two new vessels were made in which spirals of fine 

 platinum-silver wire took the place of the platinum spirals 

 previously used : the terminals were as before of stout 

 platinum wire, and the ends of the platinum-silver wire 

 (which melts at a comparatively low temperature) were 

 wound two or three times round the platinum and fused on. 

 The object of this was to eliminate irregularities due to 

 possible fluctuation in the temperature of the wire during 

 ebullition : the temperature of the wire is certainly above 



* Communicated by the Author. 



