42 IONIZATION COEFFICIENTS OF CERTAIN 



gramme-equivalent per litre, less than what corresponded to 0.2 

 of a degree. 



The freezing and melting baths were each of earthenware, 

 about 32 cm. long and with an internal diameter of about 9 

 cm. In the former was a mixture of snow and water with 

 enough common salt added to keep -the temperature at about 

 12C. The latter contained a mixture of snow and water, the 

 temperature of which was about 0.2C. 



The protection bath, which was of glass 35 cm. deep and 8 

 cm. in diameter, was provided with a covering of felt to 

 minimize the effect of the surrounding air. It contained a mix- 

 ture of snow and water with sufficient salt added to keep the 

 temperature from 0.3 to 0.28 degree below the freezing point of 

 the solutions to be measured. After some experience had been 

 gained, little trouble was found in keeping the temperature of 

 this bath constant within a twentieth of a degree during several 

 observations of any one solution. 



The freezing tubes first tried were of the following dimen- 



O * J 



sions : the inner one 22 cm. long with an external diameter 

 of 2.4 cm., the outer one 20 cm. long with an internal 

 diameter of 2.7 cm., the thickness of the glass of both tubes 

 being 1 mm. There was thus an air space of about 1.5 mm. 

 between the tubes. This was found to be too great as shewn 

 by its being difficult to prevent ice from forming around the 

 bulb of the thermometer despite the most vigorous stirring. 

 The next ones tried were as follows : The inner tube was 28 

 cm. long, with an external diameter of 2.7 cm., the outer tube 

 26 cm. long with an internal diameter of 2.85 cm., the thick- 

 ness of the glass being the same as before. There was thus an 

 air space of about 0.7 mm. between the tubes. This was found 

 to be hardly enough as there was a tendency for the ice to form 

 on the walls of the tube and thus cause much delay. As I worked 

 with 75 c.c. of solution, the greater length of these tubes allowed 

 the solution to be immersed well into the bath, rendering it 

 almost free from the influence of the outside temperature. The 



