448 



G. Barns — Ions and Nuclei in Dust-free Air, 



Art. XLYI. — Relations of Ions and Nuclei in Dust free Air; 

 by Carl Bartts. 



1. In the following table I shall give typical results of the 

 nucleation computed from the coronas observed in a glass fog 

 chamber, in the presence or absence of external radiation, when 

 the saturated dust-free air contained is suddenly cooled by par- 

 tial exhaustion of successively increasing magnitude. The 

 amount of exhaustion (with which the supersaturation goes in 

 parallel) may be conveniently specified in terms of the drop in 

 pressure, 8p, between the outside and the inside of the given 

 moderately efficient fog-chamber. Since the barometer was 

 nearly normal, the corresponding volume increase, etc., may be 

 readily derived. 



Table I. — Typical results of the ionized and colloidal nucleation of dust-free 

 air, energized (or not) by weak and strong radiation. Fog chamber about 

 50 cm long, 15 cm in diameter; walls of glass 3 cm thick, ends l cm thick- 

 Piping of one inch gas pipe. Barometer about normal. D, distance 

 between walls of fog chamber and anticathode or sealed aluminum tube 

 with weak radium. 



X 



-rays 



X- 



rays 



Radium 



X- 



rays 



X 



rays 





from 





from 



from 





from 





from 



T>= » 



end 



Z>=600 cm 



D=Q cm side 



D=100 cm 



Z>=50 cm 



dp 



n x 10- 3 . 



dp 



n x 10~ 3 . 



dp n x 10~ 3 . 



dp 



n x 1Q— 3 . 



dp 



n x 10— 3 - 



21 







19 



? 



19 '2 



18 







18 







23 



•5 



20 



2 



20 2 



19 



1 



19 



2 



25 



1'7 



21 



8 



21 10 



20 



20 



20 



*10 



27 



5 



22 



20 



22 28 



21 



37 



21 



*28 



28 



18 



23 



28 



23 38 



22 



50 



22 



57 



29 



45 



24 



33 



24 45 



24 



75 



24 



93 



30 



59 



26 



36 



25 50 



26 



95 



25 



110 



32 



73 



28 



37 



26 52 



28 



110 



27 



133 



34 



87 



30 



39 



28 53 



30 



124 



29 



145 



36 



100 



34 



41 



30 55 



35 



135 



32 



155 



-- 



-'-- 



-- 



-- 



35 56 



-- 



... 



35 



160 



In computing the (fleeting) nucleation one is left in doubt 

 whether the nuclei (ions) are restored to the air more quickly 

 than they can be removed by exhaustion; or whether the 

 reverse is true. I have assumed the former to be the case and 

 call this nucleation (number per cubic cm. ) n. If the nuclei 

 are removed more quickly than they are reproduced, it will be 

 necessary to multiply n by the corresponding volume increase, 

 and I shall call this value N. In the present experiments! JV 



* Probably reduced by the presence of persistent nuclei in small number, 

 f At high values of dp both n and N become untrustworthy as absolute 

 values; but they suffice very well to indicate the relations. 



