io8 



VAPOR NUCLEI AND IONS. 



500 



400 



300 



200 



100 



20 25 30 35 40 



Fig. 53. Efficient nucleation (n) observed in media water-air, water-C0 2 , water- 

 coal gas, energized or non-energized at different exhaustions dp. 



of air, and it was with this anticipation that the data were investigated. 

 Taken at their full value, however, they would point to a conclusion 

 exactly the reverse of this. The colloidal nuclei in C0 2 are apparently 

 smaller than in the air, and the same is true (ccet. p&r.) for the ions. 



Unfortunately the precise meaning of these results is not clear, for in 

 the first place the amount of adiabatic cooling may be written 



log r /r=(y-i)/y. log pjp 

 and thus between two fixed pressures 



log = const. 



y- 1 



^o y 



The value of this fraction is for air, 0.29; for C0 2 , 0.22 ; for coal gas, 0.19. 

 In other words, the amount of cooling is less in C0 2 than in air under like 

 conditions, and hence the reduced efficiency of the fog chamber in the 

 former case is qualitatively compatible with the thermal properties of 

 C0 2 gas. Quantitatively, however, this compensation does not seem to 

 be sufficient. For instance, the same corona is obtained in air and C0 2 

 when the pressure difference is 28 cm. and 33.5 cm., respectively. For 



