393 



violet phosphorus was chosen differently, viz. 0.9 black P and 0.1 

 violet P, and 1 7o I was again added to this mixture. The result 

 was that after IH day a' heating at 450° practically everything had 

 obtained a specific weight of 2.4, from which therefore in agreement 

 with the result of the preceding experiment, it follows that the 

 violet P is metastable at 450° under the vapopr pressure. 



It was now the question whether this could also still be demon- 

 strated at lower temperature. 



Two tubes were taken of glass that does not melt easily ; one 

 filled with Vs violet P + 7. black P, and the other with \/. violet 

 + Vs black P. Again 1 7o I was added to both mixtures. After 

 being pumped empty and fused off, the tubes were heated for 37s 

 months at 380°. When then the contents of the two tubes was 

 examined, it appeared that the mass, which at first consisted for 

 75 of violet P and for 7.5 of black P, had been quite converted to 

 rhe violet modification, whereas the mixture that at first consisted 

 for 75 of violet, and for 75 of black P, had not appreciably changed. 



To what it is owing that when the black phosphorus was greatly 

 in the minority, it was entirely converted to violet phosphorus, 

 whereas in the other case nothing could be perceived of a conversion, 

 cannot yet be stated with certainty ; the one positive result, however 

 proves already that also at 380° the black modification is the meta- 

 stable one under the vapour pressure, and this makes the view, set 

 forth in the preceding communication ^), greatly gain in probability. 



Amsterdam, April 10, 1917. Anorg. Clitm. Laboratory 



of the university. 



1) Proc. 18, 992 (1915). 



26 



Proceedings Royal Acad. Amsterdam. Vol. XX. 



