358 SCIENCE PROGRESS 



does not appear that the phenomena are due to ordinary 

 superheating. A striking feature of the observations is that 

 the vapour condenses at temperatures not widely different 

 from the true boihng point of the hquid. The condensed 

 Hquid, however, still possesses the abnormal boiling point. 

 The restoration to the normal state may be brought about 

 by admixture with small quantities of water, but the ease 

 with which this change takes place varies markedly from 

 liquid to liquid. Dried benzene could be left a day exposed to 

 moist air, without any perceptible change occurring in its 

 boiling point, and water could actually be distilled through this 

 liquid without any ebullition of the benzene occurring. On 

 the other hand, ether boiling at 83° C. was reduced to 36° C. 

 on standing in moist air for a day. The vapour pressures of 

 the dried liquids were also abnormal, at 20° C. the vapour 

 pressure of ether was 374 mm. instead of 442 mm. The surface 

 tension of dry benzene, measured by the capillary rise method, 

 was trebled by drying for a year over phosphoric oxide, although 

 no perceptible change could be observed in the density. This 

 abnormal behaviour is not confined to liquids, for solids like 

 sulphur and iodine, when strongly dried, exhibit abnormal melt- 

 ing points. 



At present it is not possible to decide with any certainty 

 as to the cause of the high boiling points ; a more complete 

 examination of the phj^sical and thermal properties of these 

 dried liquids appears to be necessary. The evidence of surface 

 tension indicates that the removal of the water has increased 

 the complexity of the liquid in some manner and has reduced 

 the concentration of the more volatile simple molecules. The 

 part played by water in this process is still obscure. 



Baly and Duncan {Trans. Chem. Soc.^ 1922, 121, 1008), 

 in experiments on the dissociation of ammonia by a hot 

 platinum wire, find that the velocity of decomposition of 

 am.monia is dependent on the rate with which ammonia is 

 withdrawn from the cylinder. Since the addition of water 

 to ammonia greatly accelerates the velocity of decomposition, 

 it appears that the observed differences are due to eht varying 

 degrees of dryness of the gas. Baly concludes that there are 

 two forms of ammonia which differ in energy content, one of 

 these being the ordinary reactive ammonia molecule, and the 

 other that form which Baker found was incapable of reacting 

 with dry hydrochloric acid. The inactive ammonia contains 

 more of the molecules with a low energy content, and slowly 

 passes, on standing over the liquid, or on heating, into the 

 active gas. Hydrocarbons also increase the reactivity of 

 ammonia ; this is interesting, since these substrnces cause 

 perfectly dry ammonia to react with hydrochloric acid. 



