500 



Frederick Guthrie on some Thermal and 



has to be watched for, the tubes cannot be enclosed in metal 

 cases for the purpose of equalizing the pressure on the glass. 

 Although only one tube of this series has burst, I have not 

 cared to carry the temperature above 180° C, which must 

 correspond to a pressure of about 15 atmospheres. 



Table LIX. 

 Separation between Diethylamine and Water as Liquids. 



Diethylamine 



Water 



Temperature at which separation 



per cent. 



per cent. 



begins. 



1264 



87-36 



Still clear at 180°. 



15-02 



84-98 



Begins to separate at 128°. 



16-30 



83-70 



121-8. 



20-94 



79-06 



121. 



26-89 



73-11 



123. 



37-80 



62-20 



128. 



45-42 



54-58 



134-5. 



62-35 



37-65 



154. 



75-76 



24-24 



Still clear at 170 (burst about 180°). 





Fig. 2. 

 Diethylamine and Water. 



Per cent. 



40 50 60 70 80 90 100 per cent. 



A few points are noticeable in these experiments. The 

 12'64-per-cent. solution showed no true separation at 180°. 

 On standing to cool, with the point of the tube a little above 

 the oil, a layer was formed on the liquid surface of about 

 1 millim. in thickness. This layer subsisted even when the 

 temperature of the bath had sunk to 100°, provided the tube 

 was not shaken. On repeating the experiment, and removing 

 the tube from the bath at 180°, it became evident that the 

 phenomenon was one of distillation. The upper and partly 

 empty end of the tube being the first to cool, the liquid 

 of highest vapour-tension, namely the diethylamine, distilled 



