4Y 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 em. long and with an internal diameter of about 9 
em. In the former was a mixture of snow and water with 
enough common salt added to keep the temperature at about 
-——12°C. The latter contained a mixture of snow and water, the 
temperature of which was about 0.2°C. 
The protection bath, which was of glass 35 em. 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- 
sions :—the inner one 22 em. long with an external diameter 
of 2.4 em. 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 
em. Jong, with an external diameter of 2.7 em., the outer tube 
26 em. long with an internal diameter of 2.85 em., 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 cc. 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 
