679 
obtained were entirely reliable, we turned back to the ordinary dila- 
tometer, and tried to attain by means of the oil of the vacuum pump of 
GorpE, which seemed to be very suitable as dilatometrie liquid, that 
no generation of gas took place at temperatures up to the melting- 
point of tin. By thoroughly boiling the oil in the vacuum of the 
pump, by then allowing it to flow into the dilatometer vessel, and 
afterwards heating the whole 20° above the melting-point of tin we 
managed to prevent any generation of gas even above the melting- 
point of tin *). 
With the dilatometer filled in this way curves of expansion and 
of contraction were determined as accurately as possible by putting 
the apparatus in a thermostat with oil resp. a molten mixture of 
KNO, and NaNO,, by raising the temperature every time 10°, resp. 
lowering it, and by then reading the position of the oil level after 
15 minutes. Though the obtained lines have not appeared to be per- 
fectly straight, as ConeN and GorpscHMipr found, yet no indication 
of a point of transition was to be detected. As according to Mr. Deauns’ 
method, by the same procedure a point of transition was found 
for tin containing mercury the mercury seemed to be a positive 
catalyst for the conversion in the point of transition. In connection 
with this we proceeded to the determination of the transition point 
of tin to which small quantities of mereury had been added. 
In this it was not only found that for every mixture very clearly 
a transition point occurred, but also that the transition point was 
greatly lowered by mercury, which is in accordance with the slight 
heat of transition. 
We found : 
at. 0/9 He 
of the mixture transition temperature 
1 0.12 73° 
z O22, 1512 
3 0.34 | 1339 
4 0.49 133° 
The third and fourth determinations point to tho existence of three- 
phase equilibrium, which is also in harmony with this that the transition 
1) Not to lose the oil during the heating up to this high temperature, the upper 
end of the capillary was provided with a wider yessel, 
