698 
only to some tenths of degrees for the thickest and the thinnest 
material. After this the measurements were carried out with thermo- 
elements of 1.4 u thickness. The temperature which these thin 
elements indicate, differs so little from that which would be found 
with an infinitely thin thermo-strip, that the remaining error may 
be neglected by the side of the other errors. 
2. We shall now proceed tu a discussion of the results of the 
measurements guided by the theory *). 
In order, however, to be able to apply the theory, and also to 
be able to calculate the temperature that has been observed, a 
number of quantities must be measured, which occur in the theory. 
These quantities are: 
1. The linear velocity of crystallisation of salol at different tempera- 
tures of the thermostat and in tubes of different internal and externa 
dimensions ; 
2. The specific heat of the solid substance and of the liquid; 
3. The melting-heat of salol; 
4. The density of the solid substance and of the liquid; 
5. The thermal conductivity of the solid substance and of the 
liquid ; *) 
6. The interior and exterior radius of the tube. 
The results of these measurements were the following: 
1. The linear velocity of crystallisation was determined in three 
different tubes, which have also been used for temperature observa- 
tions. The temperature of the thermostat ranged between about 0° 
to 29° C. Measurements of the velocity of crystallisation above a tem- 
perature of from 22° to 29°, dependent on the thickness of the tube, 
have no value. When we get too near the melting-point (42°), the 
crystallisation proceeds irregularly, and the velocity of crystallisation 
is not constant. It can be observed that the surface of the solid 
phase, which is convex and smooth and has a definite form at 
lower temperatures, becomes concave and irregular of form. Theory *) 
is able to account for this fact. 
The maximum velocity appeared to be 3.68 mm. a minute in- 
dependent of the bore of the tube‘). This value refers to pure salol. 
!) Loe. cit. 
2) | take great pleasure in expressing once more my hearty thanks to Miss A 
M. Hurrnacet for the trouble she has taken to measure these quantities. 
3) Loc. cit. 
4) The temperature of the thermostat at which this maximum occurred, does 
depend on the dimensions of the tube. 
