22 CONDENSATION OF VAPOR AS INDUCED BY NUCLEI AND IONS. 



To find S, two consecutive values of 5 suffice, or 



approximately. The diameter of particles d is, in terms of n 



d 9 6m Inn 



If X= 54. 6 X io~ 6 cm. is the wave-length of green mercury light and 

 the angular radius of the first green minimum of the coronas, sin 0<=o.6i 

 \l(d' /2). Since sin d = s/2R, R being the radius of the goniometer of 

 which 5 is the chord, d' the diameter of fog particle (the primes referring 

 to optic measurements), 



d' = 0.004/5 



for mercury light. Hence optically the nucleation is 



io~ G n f = 2 9. 8ms 3 



where m grams of water are precipitated per cubic centimeter on ex- 

 haustion, and found in the exhausted fog chamber. 



24. Data with white light. The results in the following tables are 

 reported in accordance with the same plan throughout. The fog chamber 

 is initially at atmospheric pressure p, the vacuum chamber exhausted to 

 p dp f . When the exhaustion cock is closed 5 seconds after exhaustion, 

 the pressure in the fog chamber, after the original temperature is rees- 

 tablished, will be p [dp2\. The common isothermal pressure in vacuum 

 and fog chambers when communicating after the exhaustion is eventually 

 p p 3 . If Ti is the vapor pressure at the given (isothermal) temperature, 

 the exhaustion ratio is 



The amount of water precipitated per cubic centimeter is m at the 

 temperature and pressure given. 



TABLE 9. -Standardization of the fog chamber. Welsbach burner and phosphorus. 

 Cock open 5 sec. Observation interval 60 sec. Bar. 75.9 cm. at 22. Temp. 26. 

 [o>,] = i6.5 cm.; 5/> 3 = 17.4 cm.; dp'=i8.6 cm.; y= (l>-it-[dp 2 ])/(p-it) =0.775; 

 df> 3 '/p = o.22g; io fi m = 3.77 grams at 20; 4.22 grams at 26; 11 = 2.5 cm. Gonio- 

 meter in front. Distances of eye and lamp 30 cm. and 250 cm., on opposite sides 

 of fog chamber. Radius of s, R = 3O cm. 



*Two identical series beyond this. 



