522 



Scientific Proceedings, Royal Dublin Society. 



the volume constant was compared with one in which the water was allowed to 

 pass through a tube leading to the surface of the solution. In the latter case 

 the rate of distillation was found to be higher. By replacing the cold liquid 

 by water which had been heated, it was shown experimentally that the 

 amount- of condensation was still further reduced, and in order to bring this 

 to a still lower figure it was decided to introduce the liquid (distilled water 

 free from C0 2 ) through a side tube sealed into the flask below the level of the 

 solution. All risk of cooling the vapour by the entering liquid was com- 

 pletely avoided. The flask with the side tube was made of quartz, and was 

 supplied to our design by the Silica Syndicate, Ltd., London. In a later form 

 of the apparatus the side tube sloped at 45° to the horizontal for a short 

 distance outside the flask before becoming vertical. 



Table 3. 



It was also found when the distillation flask was surrounded by a steam- 

 jacket that not only was the amount of condensation in the stillhead reduced, 

 but the rate of distillation was considerably more uniform. The steam-jacket 

 consists of a conical-shaped copper vessel with two slots for the passing of 

 the tubes— one at the top to carry the tube leading away the distillation pro- 

 ducts, and the other at the base, on the opposite side, for the tube leading 

 to the bottom of the flask. The method of arranging the steam-jacket is 

 shown on Plate XLIX. The electric hot-plate which supplied heat to the 



