i06 



lution ligiiies, and also resolutions of tlie abnormal sign, can appear, 

 and that negative rotation might arise in consequence. 



The thought suggests itself to try whether the observed rotation 

 constants can be explained in this way. For this purpose it is neces- 

 sary to represent these constants by a formula as required by 

 theory, with one or more ultraviolet frequencies. It will have to 

 appear at the same time that the index of refraction can be repre- 

 sented by a formula of the form required by theory, with the same 

 frequencies, besides ultrared ones. 



It will be communicated in a following paper what a treatment 

 of the results of our observations in this sense will have vielded. 



Chemistry. — -'Oti Tension Lines of tite System PhosphorKs." IV. 

 By Prof. A. Smits and S. C. Bokhorst. ^Communicated by 

 Prof. J. D. VAN DER Waals.) 



(Gommuuicated in the meeting of April 23, 1915.) 



1. y^ein determinations of the vipour jjressure of liquid irhite 

 p/iosplwriis. 



In the first communication under this title ') among others the vapour 

 pressure line of the liquid white [)hosphorus was discussed. This 

 line, which had been determined by us according to the statical 

 and dynamical method up to 336°, had such a course, that it could 

 not be considered as the metastable prolongation of the \apour pres- 

 sure line of the liquid violet pliosphoms. 



Now it appeared that this result was to be ascribed to this that 

 the vapour pressure above 325° increased with the temperature to 

 an abnormal degree. 



This circumstance added to the fact that the temperature was 

 always increased as quickly as possible in the vapour tension deter- 

 mination to prevent all the white phosphorus from being converted before 

 the detei'mination could be made, led us to suppose that the results 

 might be faulty at these high temperatures in consequence of spon- 

 taneous heating of the mass brought about by the conversion : 



white F-* violet P + « Cal. 

 1) These Proc. Vol. XVI, p. 1174. 



