1174 



Chemistry". — "On tJic rupniu- prcssi/n' lines of the si/sfiun phos- 

 phorus." I. By Prof. A. Smits. S. C. Bokhorst, and J. W. 

 TERWfc'.N. (Coiniimuicaled by Prof. J. D. van dek Waals). 

 (Communicated in the meeting of March i28, 1913). 



1. On a former occasion ^) the result of a preliminary investi- 

 gation about the vapour pressure lines of liquid white and liquid 

 red phosphorus was communicated. It appeared already then that 

 the vapour pressure lines of these two colourless liquid phases of 

 the system phosphorus cannot be considered as two pieces of the 

 same vapour pressure line. 



The question under discussion l)eing of the utmost importance, 

 which ought to be decided with perfect certainty, it was resolved 

 to determine the vapour pressure lines of liquid white and liquid 

 red phosphorus as accurately and as far as possible. 



2. Determination of the vapour pressure line of liquid red phosphorus. 

 We again made use of Jackson's glass spring manometer (see fig. 



1 ab), which was now made of infusible glass, was filled with pure 

 red phosphorus, and then exhausted and sealed off. This glass spring 

 served as phosphorus reservoir and at the same time as indicator 

 of the pressure. 



Round the glass spring a wider vessel c had, namely, been sealed 

 on beforehand, which ended into a somewhat narrower tube, which 

 was electrolytically coated with copper at e, so that it could be 

 soldered to the copper mounting >\ 



This copper mounting consisted of a copper coupling piece, in 

 which a copper plate was used as packing. The said mounting was 

 in connection with the cocks K^ K. by means of copper tubes, and 

 the pressure cylindre (/, which was tilled with glycerin, and was 

 connected with a Schaffer and Budenberg's hydrostatic press A 

 with closed air manometer J/,, and metal manometer M^. 



The cock K^ could effect the communication between the space 

 round the glass spring and the carbonic acid cylindre ^V, and the 

 cock K^ could bring the same space into communication with the 

 open manometer M^. A T-piece with the cocks K^ and /i, was 

 sealed to this open manometer, K^ being connected with the Gaede 

 pump. Before the beginning of every experiment the space round 

 the glass spring was exhausted through this cock, to have an oppor- 

 tunity to indicate the zero-position of the needle of the glass spring 

 on the tube d. This was effected by sticking two strips of paper 



1) These Proc. XV, p. 885. 



