400 C Barns — Possibility of a Colloidal State of Gases. 



Art. XXXIII. — Note on the Possibility of a Colloidal State of 

 Gases ; by C. Barus. 



1. In a survey of the diffusion rates of* nuclei derived from 

 the same source and under otherwise like conditions, but sus- 

 pended in different media (i. e., in air saturated with different 

 vapors), the occurrences may be classified with reference to 

 two extreme types : The first includes vapors derived from the 

 strongly ionizing liquids like water, methyl alcohol, ethyl 

 alcohol, etc. In these cases the coronas obtained on suc- 

 cessive condensation by the exhaustion method are always 

 regularly annular, or at most distorted in color only. With 

 water vapor the coronas do not even show color distortion. 

 With the alcohols the coronas may show the colors of two suc- 

 cessive coronas* in the upper and the lower halves of the same 

 rings, but there is no distortion of form appreciable. 



The second type of phenomena are observed with vapors 

 derived from the non-ionizing liquids, like the hydrocarbons 

 gasolene, benzine, etc., carbon bisulphide, benzol, toluol, etc., 

 in which the successive coronas show gradually increasing dis- 

 tortion of form. If the original corona is annular and the 

 distribution of nuclei therefore uniform, the following coronas 

 pass through campanulate distortionf and finally become mere 

 color strata. 



2. The effect of the successive precipitations is a disturbance 

 of the original homogeneous nucleation. The degree to which 

 the uniform distribution will be kept up depends, therefore, 

 on the rate of diffusion of the nucleus. It follows that the 

 nuclei of the first group must diffuse very rapidly so that all 

 parts of the receiver continually contain about the same num- 

 ber per cubic centimeter. The effect of removal of nuclei by 

 loading is thus quickly wiped out. On the other hand, the dif- 

 fusion of nuclei in the second group (non-electrolytic solvents) 

 is enormously slow, by comparison. It is quite possible to 

 observe the air in the lower half of the receiver full of nuclei, 

 w T hile the upper half is air free from nuclei, or to bring about 

 other similarly stratified conditions evidenced by semi-coronas, 

 quarter coronas, etc. Indeed when foreign nuclei are intro- 

 duced they are usually seen on exhaustion to be distributed in 

 layers, usually in couches immediately over the surface of the 

 liquid. The rates of diffusion are here easily measured and of 

 the order of *01 to '02 cm/sec. ; whereas in the case of electro- 

 lytic solvents, measurement is difficult, not only because the 

 diffusion is over 100 times faster, but because the advance of 



* This Journal, xiii, p. 81-94, 1902. flbid., xiii, pp. 309-312, 1902. 



