922 Research Staff of the Gr. E. C, London, on the 



third the difference P. The variations between successive 

 determinations are greater than can be attributed to experi- 

 mental error in measuring the pressure, but there is no 

 consistent variation of P with p. 



Table I. 

 p+p. p. P. 



(Original pressure.) (Final pressure.) (Absorbed.) 



0-491 mm. 0'457 mm. ' 0034 mm. 



•382 -330 -052 



•293 '265 -028 



•284 -250 -034 



•233 -192 -041 " 



•174 -139 -035 



•119 -081 -038 



•102 -053 -049 



•093 -058 -038 



•061 -032 -029 



•035 -000 -035 



0-150 '084 -066 



•109 -040 -069 



•094 -035 -059 



•083 -032 -051 



•068 -000 -068 



It is apparently permissible to speak of a definite amount 

 of gas absorbed with a given amount of phosphorus, 

 independent both of the nature of the discharge and the 

 pressure of the gas through which it passes. 



7. If such independence is established, factor (2) can be 

 isolated. Fig. 1 shows the relation, determined by obser- 

 vations on some 250 lamps by the method of Par. 4, between 

 the amount of phosphorus introduced into the lamp and the 

 amount of gas that can be absorbed, both amounts being 

 expressed in milligrams. The points ( x ) joined by full lines 

 were obtained when the experiments are conducted in the 

 manner described. The features to which attention for 

 subsequent discussion is drawn, and which are repeated in all 

 other observations despite variations in detail, are : — 

 (1) The general increase in the hydrogen absorbed with 

 increase of phosphorus. (2) The maximum followed by a 

 decrease. (3) The general slope of the line which, even if it 

 were smoothed into a straight line, would not suggest any 

 chemical combining proportions of the two elements, e. g. 

 10-3 to 1 (PH 3 ) or 31 to 1 (P 2 H 2 ). (4) The marked " step " 

 in the line from 0*09 to 0*27 mgm. of phosphorus ; there are 

 distinct indications of similar but less marked steps at the 

 points for lower values, and even at the higher values 

 considerable variations of the amount of phosphorus about 



