1 1 6 THE STRUCTURE OF THE NUCLEUS. 



he caused by auy species of decay due to the iuteiactiou of iLe luiolei. lu the light 

 ■ >f all that follows it has seemed to me that the hypothesis of diffusion and loss at 

 the walls of the vessel is in best agreement with the data as a whole, and the 

 results are therefore interpreted from this point of view. (6/. § 2.) 



As the pressure decrement is IG cm., the nucleation, n, may be computed, as 

 already specified, from n ■= 47 s^ . Tlie residts are given in table 1 and the chart, 

 fii^ure 5. The time losses per minute are on the average about .li>, so that over 5 

 minutes would be needed to remove a single nucleus or over (! houi-s to remove the 

 initial number of 71 particles at the same rate. But as this rate is not generally 

 even approximately constant, it is expedient to compute k as in the next paragrapli. 



9. Absorption velocity. — If llie loss of nuclei be due to their absorption at 

 the boundary of the vessel with a velocity, h, so that hii, nuclei are aVisorbed there 

 per minute per s(juare centim., sup[)i)sing that a mere radial march of nuclei 

 outwai'd occurs, or that the diaiii of nuclei is from the content of the receiver as a 

 whole, the nucleation will decrease exponentially. Briefly, 



11 — . II e , 



where n and //' are the nucleatious at the times / and t , and where li is the radius 

 (15 cm.) of the spherical receiver. Coml)iiiiiig the above results in pairs, the mean 

 value h = .016 cm/niin. follows from the four available observations, with some dis- 

 (•rej>ancy as the observations happen to confoiin closely to a stiaiglit line. The 

 number thus obtained is from 600-lOUO times smaller than the numbers found 

 from similar hypotheses for the velocity of fresh phosphoius nuclei in air. From 

 this one may infer in a general way that the nucleus in water vapor is a relatively 

 large body as compared with the nucleus of the same origin in case of air. The 

 phosphorus nucleus in the same receiver but under conditions of much denser 

 nucleation showed ^' = .096 cm/min., and thus the following data for the absorption 

 velocity have appeared : 



Fresh phosphorus nuclei, in air, k = .3 cm/sec. 



Dense phos|)horus nuclei in water vapor, .0016 



Sparse nuclei due to shaking dilute HCl, .00026 



results apparently due to successively' larger diameters. But the last value of h is 

 iinusnaily low and rather in the nature of an infi-rior limit. \'alues five times larger 

 {Of. table 11) ate not unusual with IICI, and in jnoportion as water is approached 

 in very dilute solutions, the value of h may actually be as high as over one half 

 the air value cited. 



10. Repetition. — In a repetition of the experiments with llC'l, the above 

 exceptionally low values of n and h were not again obtained. As seen in table 14, 

 for a series of diluted solutions of .5 %, .005 ^ and .00005 %, the constants approach 

 verj' closely to the usual order of values for salt solutions. It is difficult in a vessel 

 containing metallic parts, ruVjber tubing, etc., to escape the introduction of impiuities 

 from so corrosive a body, notwithstanding the caution naturally taken with the 

 work. But tlx- difference remains unexplained. 



Another peculiar feature met with in case of this volatile acid is the difficulty 



