on the Emanation of Phosphorus. 329 



be used. This was only done when specially called for in the 

 present work, where the form of the temperature function is 

 the chief consideration. 



3. Method and data. — The usual method of experiment was 

 adopted, the liters per minute (d Y/dt) of saturated phosphorus 

 air necessary to produce the fiducial blue of the color tube, 

 being observed at different temperatures. The data are given 

 in Table I, in the first part of which observations for falling 

 temperature, and in the second for rising temperature, are 

 recorded. The pressure of the steam jet was about p=4t to 

 6 cm . The inflowing air showed a temperature of 27° to 28°. 

 The table contains some other colors (including opaque) for 

 orientation. 



The chief data of the table are reproduced in the chart 

 figure 3 (p. 334) and show the sudden cessation of reaction at 

 12°-13°. 



4. Discussion. — For the sake of preliminary comparisons 

 with the corresponding electrical charts given below, it is well 

 to lay off l/(dV/dt) in its variation with temperature : for this 

 reciprocal runs parallel to the concentration of the emanation 

 producing the color. The construction is given in figure 4, in 

 which the sudden rise of activity in producing nuclei is apparent 

 at 13°, and the subsequent gradual decline thereafter as far as 

 examined, is again manifest. Anticipating data of subsequent 

 paragraphs, I may add that the maximum ionizing activity is at 

 20°, showing the two thermal relations to be non-coincident. 



The charts show in the first place, that as temperature falls 

 from the highest admissible values, say 35°, the emanation of 

 phosphorus actually increases* at a rate of about 2 per cent per 

 fall of 1° C. The maximum activity occurs at about 13°, and 

 is upwards of 25 per cent greater than at 30°. Between 12° 

 and 13°, however, the emanation is quenched at an enormously 

 rapid rate, falling just short of suddenness. Practically, there- 

 fore, the reaction begins at about 13°, with full if not greatest 

 intensity. 



Below 12°, the emanation is insignificant and the maximum 

 permanent colors obtainable are faint blue grays, even when 

 the gasometer flow is forced to, say 400 liters/minute. There 

 are no opaques. Below 10° there were no permanent colors 

 discernable. 



5. Here, however, and slightly above and below this tem- 

 perature, definite pitffs of color or of darkness are obtained 

 immediately after opening the faucet suddenly. The phe- 

 nomenon may be repeated indefinitely by closing the faucet 



*This increase maybe due to the gradual thorough desiccation of the phos- 

 phorus by the dry current of air. These grids were not dried preliminarily over 

 calcium chloride. 



