185 



Fig. 1. 



As point of solidification Rupert determines the point at wiiich 

 the crystals bronght into the liquid no longer grow or disappear. 

 He measures the temperature accurate down to 0°.5 with a verified 

 toluol-thermometer. Below — 100° he uses a thermo-element, tested 

 by comparison vA^th the toluol thermometer aud with the boiling 

 point of liquid air. He himself considers the determinations with 

 this thermo-eieinent insufficient, which tallies with our results, as by 

 extrapolation about — 125° may be derived from Rupert's investigation 

 for the temperature of the eutectic point NH3.H2O -|- H^O -|- L, 

 whereas this point lies certainly 24° higher according to Fig. 1. 



Leaving the region of concentration 30 — 407o out of account, the 

 agreement between Rupert's results and ours is fairly satisfactory. 

 If we compare the principal points, we get what follows : 



