Ii8 Conductivity of Aqueous Solutions. Part V. 



. HEATERS. 



The conductivity measurements were made at 18 and approximately 

 100, 156, and 218. The first of these temperatures was secured with 

 a bath of liquid xylene contained in a well- jacketed metal cylinder. The 

 temperature was regulated by the observer, the bath being heated elec- 

 trically by means of a resistance coil and cooled by a coil of lead pipe, 

 through which cold water was passed. The bath was constantly stirred by 

 a propeller. The' temperature could be maintained constant to within 

 0.01. 



The 100 heater was a double-walled copper cylinder heated by steam, 

 similar to that described in section 32, Part IV. 



The 156 and 218 baths were of the form described in the article by 

 Noyes and Coolidge.* Brombenzene and naphthalene were used as boiling 

 substances, the latter substance proving very satisfactory throughout. 

 The temperature of the brombenzene bath remained constant through sev- 

 eral successive heatings, but in time a slight decomposition necessitated 

 the substitution of fresh liquid. The same shielding devices for securing 

 uniform temperature were employed as in the previous work. 



THERMOMETERS. 



Three different thermometers were used in the work a 0-60 ther- 

 mometer, reading directly to tenths, for the 18 bath, an ordinary Beck- 

 mann style thermometer for the 100 bath, a French mercurial 360 

 thermometer made by Alvergniat, No. 65650, for the two vapor baths. 

 The 18 point of the first thermometer was determined by comparison with 

 a standard Baudin thermometer. The steam point of the Beckmann ther- 

 mometer was determined each time by introducing the thermometer into a 

 boiling-point testing apparatus of the Regnault type immediately before or 

 after each 100 measurement. The Alvergniat 360 thermometer was 

 similarly calibrated for the 218 point at frequent intervals by immersion 

 in a vapor bath of specially purified naphthalene of the type recommended 

 by Crafts. f For the 156 point the bore was calibrated by the method rec- 

 ommended by Crafts and the value of the scale unit was determined from 

 the interval between the steam and naphthalene points. The temperatures 

 lying between the fixed points were reduced to the gas scale by using 

 Crafts' table of corrections for French glass, our thermometer being of the 

 same make as those used by him. For the boiling point of naphthalene, 

 however, the result more recently obtained by Jaquerod and Wassmer % 

 was adopted. 



*Section 3, Part II. 



fAm. Chem. J., 5, 307-338 (1883-84). 



jj. chim. phys., 2, 72 (1904). 



