342 0. Ba/rus— Vapor Nucleation in the Lapse of Time. 



Art. XXXII. — Vapor Nucleation in the Lapse of Time / by 



C. Baeus. 



1. Nueleations depending upon $p/p. — As contemplated in 

 my last article,* I have since computed the nucleation of dust- 

 free wet air in the lapse of time in terms of the relative drop 

 Bp/p, where &p=p—p 1 , the difference between the atmos- 

 pheric and the adiabatic pressure in the fog chamber after 

 exhaustion. I have also taken advantage of new tables for 

 the expression of nuclei per cubic centimeter in terms of the 

 apertures of corresponding coronas, based on data since inves- 

 tigated. The nueleations to be compared in the lapse of time 

 were all reduced to the fiducial values of the relative drop 

 Sp/p = - 345, which is sufficiently near the region of ions for 

 practice, and sufficiently large to insure moderate-sized coronas. 



Omitting the tables, I will give the data for the vapor 

 nucleation of the dust-free wet air in the fog chamber and the 

 corresponding temperature in the accompanying graphs, the 

 abscissas showing the running dates. The ordinates are aver- 

 aged in groups of from two to four successive days, as in the 

 last paper. It is in this presentation that the issue of greatest 

 moment will appear, for the nueleations in their narrower 

 variations (from hour to hour) are similar to those already 

 shown (1. c). The data for n. 3i6 have been corrected for the 

 effect of temperature, t, on the amount of water precipitated, 

 by taking from the recent results referred to, the temperature 

 coefficients 8?i/n8t, an example of the values for different 

 relative drops being : 



8p/p = -1 -2 -3 -4 -5 



]0 5 x8n/n8t = 14 18 23 27 30 



These data would not, however, seriously modify the trend of 

 the curves. 



The graph shows that the effect of temperature in the lapse 

 of time has not been eliminated by replacing the extreme 

 variable (S^> — (7;- — 7r 3 ))/(j? — 7r) by the other extreme variable 

 8p/p. In other words, if the nucleation corresponding to a 

 fixed exhaustion 8p/p = -345 is studied in the lapse of time, 

 the successive nueleations show a dependence on the tempera- 

 ture of the fog chamber which can no longer be explained 

 away. Both the details and the general character of the 

 graphs for n. SA5 follow the fluctuations of temperature to an 

 extent which may be estimated from the figure as an incre- 

 ment of about 2000 nuclei per rise of temperature of 1° C. 

 * This Journal, xxiii, 1907, § 10, p. 209. 



