( 104 ) 



We then notice the peculiar phenomenon that the compound is 

 apparently quite solid till close to the melting point and we find 

 for the vapour pressure the curve CTF, whilst the superfused liquid 

 gives the vapour pressureline FA^ which is situated much lower. 

 Ramsay has found this previously without being able to give an 

 explanation, as the situation of the three-phaseline was unknown 

 at that period. 



In the case of anilinehjdrochloride, it was not difficult, on 

 account of the great volatility of HCl, to determine sublimationlines 

 when an excess of this component was present. In Fig. 2 two such 

 lines are determined BE and B^E^. From ^^ the three-phaseline was 

 followed over the piece E^H^ afterwards the liquid-vapourline i:/i/i. 

 From E also successively EH and HI. With a still smaller excess 

 of hydrogen chloride we should have stopped even nearer to F on 

 the three-phaseline. 



In the case of chloralalcoholate we noticed also the phenomenon 

 that a solid substance which dissociates after fusion may, when 

 heated not too slowly, be heated above its meltingpoint, a case lately 

 observed by Day and Allen on melting complex silicates, but which 

 had also been noticed with the simply constituted chloralhydrate. 



An instance of the third type of a three-phaseline where the 

 maximum and minimum have disappeared in the lower branch of 

 the three-phase line has not been noticed as yet. 



The two types now found will, however, be noticed frequently 

 with other dissociable compounds such as those mentioned above, 

 and therefore enable us lo better understand the general behaviour 

 of such substances. 



Physics. — " On the polarisation of Röntg en rays." By Prof. H. Haga. 



In vol. 204 of the Phil. Trans. Royal Soc. of London p. 467, 

 1905 Barkla communicates experiments which he considers as a 

 decisive proof that the rays emitted by a Röntgen bulb are partially 

 polarised, in agreement with a prediction of Blondlot founded upon 

 the way in which these rays are generated. 



In these experiments Barkla examined the secondary rays emitted 

 by air or by some solids: paper, aluminium, copper, tin, by means 

 of the rate of discharge of electroscopes. In two directions perpen- 

 dicular to one another and both of them perpendicular to the direction 

 of Ihe pi'iniary rays, he found a maximum and a minimum for the 

 action of the secondary rays emitted by air, paper and aluminium. 



