NUCLEI IN ALCOHOL VAPOR. 113 



ethyl alcohol and air in comparison with the media of water-air and 

 water-carbon-dioxide hitherto examined. The former behaves in fact 

 as if the nuclei were throughout larger than in the latter cases. 



77. Apparatus and method. The experiments were conducted with 

 an apparatus in which the connecting pipes between the fog chamber 

 (18 inches long, 5 inches in diameter) and the vacuum chamber (5 feet 

 long, 1 foot in diameter) were 4 inches in diameter, containing a 4-inch 

 counterpoised plug stopcock. The whole connecting system was about 

 22 inches long, one-half of it belonging to the fog chamber. Experiments 

 made with water vapor, however, did not show any further marked 

 advantage arising from the use of the large passage-way specified, over 

 the former apparatus, in which the corresponding tube was 2 inches in 

 diameter. It is therefore superfluous to adduce for comparison the new 

 data for water vapor. The general method for work was that frequently 

 described in connection with these investigations. 



78. Properties of alcohol fog. While the experiments of my preceding 

 paper with the medium of water vapor and carbon dioxide gas showed 

 unusually high values of the exhaustions needed to produce coronal 

 condensation, the case of alcohol-air shows correspondingly low values 

 of exhaustion as compared with those for water-air. The number of col- 

 loidal nuclei entrapped by alcohol vapor are about 3.5 times larger than is 

 the case for water vapor under like conditions. Hence the coronas for 

 alcohol are exceedingly dense by contrast. They are also much less pure 

 in color, and particularly at high exhaustions become fog-like. The 

 phenomenon is coarsened and measurement less satisfactory. 



As the alcohol fog particles are larger in size, they subside more rapidly 

 at the same exhaustion than water particles; but the occurrences are 

 in the former case far from simple. While the corona (if not too large) 

 remains nearly the same throughout the slow subsidence of water parti- 

 cles, the corona for alcohol particles decreases one-half or more in size 

 during this period. In other words, the alcohol particles experience 

 very rapid growth during subsidence, from which it follows that many of 

 them must evaporate to compensate in part for the eight-fold or more 

 enlargement in bulk of the survivors. The same fact may account for 

 the blurred coronas; for the true initial corona being very evanescent 

 is probably not seen. Conformably with this view it is impossible to 

 exceed large white-reddish forms in the present apparatus and to reach 

 the high greens observed with water vapor. 



79. Number of particles. In order to determine the number of particles 

 corresponding to a given corona, it is first necessary to compute the 

 amount of alcohol precipitated per cubic centimeter of the exhausted 



