I2o VAPOR NUCLEI AND IONS. 



ration form a system in contact. In case of water vapor the distance 

 between centers would be 0.014 cm.; in case of alcohol 0.010 cm., dis- 

 tances which are both enormous as compared with the estimated size 

 of nuclei (r, table 45, fig. 54). The greater distance which belongs to 

 water vapor would be in keeping with its greater diffusivity, though this 

 surmise does not work out for water-carbon dioxide as compared with 

 water-air. At all events, when the limiting number of nuclei has been 

 captured, the apparatus is powerless to produce condensation on a 

 greater number of nuclei, be they relatively large as the ions or small 

 as the colloidal nuclei, however many other inefficient nuclei may be 

 present. 



ABSENCE OF COLLOIDAL NUCLEI IN STRONG ODORS. 



82. Introductory. Throughout the course of my work I have been 

 endeavoring to find whether bodies with strong odors and presumably 

 large molecules could be regarded as a source of colloidal nuclei; or 

 whether there is any relation between the colloidal nucleus and the 

 odors. In case of carbon disulphide, from which nuclei apparently 

 escape spontaneously, this would seem to be the case; but it is yet to be 

 proved that vapor of carbon disulphide, if carefully filtered, neverthe- 

 less still produces colloidal nuclei in the fog chamber. In the present 

 instance it is not improbable, if relatively few CS 2 molecules are oxidized 

 S0 3 , that sulphuric acid nuclei are the result. The experiment which 

 has already been discussed is well worth while; but I did not make it, 

 in the fear of contaminating the vacuum chamber. The following experi- 

 ments show, however, that even in the extreme cases odors are due to 

 molecules, and that in relation to the fog chamber, apparently large mole- 

 cules are still quite negligibly small in comparison with the colloidal 

 nuclei. 



83. Data for camphor, turpentine, naphthalene. The results obtained 

 are given in table 47 in the usual way. The glass fog chamber was 

 provided with a hole in the (thick) bottom, about 2 cm. in diameter 

 and closed with a rubber cork. It was free from leakage from without. 

 The bodies to be examined were introduced through the hole in question, 

 and suspended in the middle of the fog chamber by aid of a wire-gauze 

 tube 20 cm. long and 2 cm. in diameter. After putting this tube in 

 place the air was carefully cleansed by precipitation of dust. 



On May 5, 6, and 7, after putting the apparatus together, the medium 

 within was first examined without introducing the odoriferous body. 

 The internal sources of spurious nucleation gradually vanish. The 



