KAHLENBERG — THEOEY OP ELECTROLYTIC DISSOCIATION. 305 



molecular weight than by the but too common practice of com- 

 paring dissociation coefficients deduced from conductivity re- 

 sults obtained at room temperature, with those reckoned from 

 boiling- or freezing-point experiments. The work of making 

 the conductivity measurements at high temperatures and the 

 corresponding boiling-point determinations was undertaken by 

 Mr. Arthur A. Koch, to whose diligence and care the numerous 

 tables (2 and 12 to 31, inclusive) given below are due. Again 

 it was part of the plan to measure the conductivity of such solu- 

 tions at 0° and at the same time to make molecular weight deter- 

 minations by the cryoscopic method, and then to compare the 

 degrees of dissociation found according to the two methods. 1 

 All the conductivity determinations at 0° were made by Mr. 

 Roy D. Hall, the results of whose work are contained in Table 

 1 below. 



The conductivity determinations were made by means of the 

 usual Kohlrausch method, a telephone being employed. An 

 Arrhenius resistance cell was used for the dilute solutions, and 

 a U shaped cell with plantinized electrodes sufficiently far apart 

 was employed for the concentrated solutions. All of the solu- 

 tions were carefully made up to the proper volume at the tem- 

 perature indicated. The measurements at 0° were made in a 

 bath of melting ice surrounded by another very large bath of 

 the same nature. In the immediate vicinity of the resistance 

 cell a delicate thermometer was kept which remained very con- 

 stant at 0°. At first it was attempted to measure the conduc- 

 tivity of solutions at 100°, but it was soon observed that small 

 gas bubbles are so apt to form on the electrodes at this tempera- 

 ture as to introduce considerable error. It was found that at 

 95° this particular difficulty is not so prominent, and so the con- 



1 Bat few conductivity determinations at or near 100° could be found in the 

 literature. For seven of the salts named in Table 2, Krannhals [Zeit. phys. 

 Chem. 5, 250 (1890)] determined the conductivity at 99.4°. He did not, however, as 

 a rule begin with as concentrated solutions as those represented by the corres- 

 ponding salts in Table 2, and his series are frequently incomplete. As far as 

 conductivity determinations at 0° are concerned only a few scattered determina- 

 tions could be found In the literature, which would not have been adequate for 

 the purpose in hand. Molecular weight determinations of a goodly number of 

 the salts under consideration are to be found in the literature, but. they do not 

 cover a sufficient range of concentration for the present purpose. 



