on the Emanation of Phosphorus. 345 



Since from the old values the number of nuclei was computed 

 as w = 2xl0 4 , the new values would make them approach 

 ft, = 4Xl0 4 , the datum found with plate and with spherical 

 condensers by entirely different methods, remembering that 

 from the occurrence of an absorbing influx pipe, the air 

 within the tubular condenser can nowhere be quite saturated. 



Experiments on the maximum number of nuclei per cubic 

 centimeter producible by phosphorus under favorable condi- 

 tions, were made at some length ; but as they yielded no new 

 results beyond those of § 23, they need not be instanced here. 



25. Conclusion and summary. — The experiments with phos- 

 phorus show that nuclei adapted to condense atmospheric 

 moisture are produced most abundantly at about 13° C. Below 

 this, the rate of production decreases with enormous rapidity 

 (just short of suddenness), probably ceasing at about 8°. This 

 holds true for very different velocities of the dry air passing 

 over the phosphorus. Above the reaction temperature, the 

 activity decreases slowly as temperature rises, having not 

 decreased more than 25 per cent at 35°. Since the phosphorus 

 is superficially heated by the reaction, sharp statements are out 

 of the question. 



Below 13°, the opaques of the color series are absent and 

 the maximum tints are fainter and of increasingly higher 

 orders. The strongest permanent color may be approached by 

 very gradually increasing the charged air current. A limiting 

 velocity decreasing with temperature may thus be reached, 

 beyond which all colors vanish and the reaction is quite 

 " blown out," as it were. Suddenly opening the stopcock 

 after a period of quiescence shows puffs of color under these 

 conditions, which also vanish as temperature decreases below 

 13°. Putting JV — hi, where JV is the number of particles 

 generated per second per superficial square centimeter of phos- 

 phorus, n the number per cubic centimeter of the ionized 

 medium, k their (average) velocity in any cardinal direction, 

 the variation of JV is to be ascribed to n, k being relatively 

 constant. 



In contrast with the color data (nuclei), the ionization of air 

 passing over phosphorus increases with temperature to a maxi- 

 mum at about 20°, after which there is a less pronounced 

 decline. This ionization is not an arrival comparable in sud- 

 denness with the appearance of nuclei, nor are the maxima 

 identical as to temperature. One may infer that the nuclei as 

 first produced are weak in ionization but of normal strength in 

 condensational activity ; that thereafter the latter property 

 declines because (probably) the ionization increases as far as 

 20°. Finally both properties decline. This reciprocity is 

 accounted for if the ionization is a result of the dissociation of 



