RESIDUAL WATER NUCLEI. 



103 



63. Persistence of water nuclei. If there is a difference between 

 the water nuclei obtained after evaporation of fog particles precipitated 

 upon ions and those precipitated upon vapor nuclei, this should show 

 itself in a corresponding difference in the length of life of the types of 

 water nuclei in the two cases. Incidentally the number of nuclei dissi- 

 pated upon evaporation must appear in the graphs. 



The data of the experiments are given in table 44, where n shows the 

 number of nuclei in the original fog precipitated upon ions or on vapor 

 nuclei and n' the number of residual water nuclei after the evaporation 

 of the first fog. In series I the filter cock was open after the measurement 

 of the first corona and the exhaustion used in the precipitation upon vapor 



100 100 300 400 SOO 600 100 800 900 



FIG. 32. (a) Persistence of residual water nuclei obtained from the evaporation of 

 fog particles precipitated upon ions and vapor nuclei. The curve shows the number 

 n of water nuclei left i seconds after evaporation, (ft) Comparison of water nuclei 

 obtained from evaporation of fog particles precipitated upon phosphorus nuclei and 

 ions, in successive identical exhaustions. (Note the conspicuous loss in evaporation 

 between the first and second precipitations.) 



nuclei was greater than it was in the corresponding case for ions. These 

 objectionable features were removed in the second and third series, where 

 identical exhaustions occur throughout and the graduated filter cock (fine 

 screw-valve) was opened to a definite number of degrees (30). After 

 about 60 the resistance of the long filter prohibited a more rapid influx. 

 The results are all shown in fig. 32, a, with the series suitably dis- 

 tinguished by crosses, and they are referred throughout to an initial 

 nucleation of 86,000 per cubic centimeter. The data show, in the first 

 place, that somewhat more than one-third of the original number of 

 ions or of vapor nuclei are represented by these residual water nuclei, 



