CHAPTER IV. 



DISTRIBUTION OF COLLOIDAL NUCLEI AND OF IONS IN MEDIA OTHER 



THAN AIR- WATER. 



COLLOIDAL NUCLEI AND IONS IN WET DUST-FREE CARBON DIOXIDE 



AND IN WET COAL GAS. 



67. Apparatus. The following experiments were made with the 

 apparatus used in my last experiments* with dust-free air. The con- 

 veyance tubes between the exhaustion chamber (5 feet long and 1 foot 

 in diameter) and the condensation chamber (18 inches long and 5 inches 

 in diameter) were about 18 inches long and 2 inches in diameter. The 

 rapid exhaustion thus secured is effective, but has by no means reached 

 a limit; there is still too much resistance in the connecting pipes. The 

 data obtained with such an apparatus are comparable with each other, 

 and nothing further than this is aimed at, since in view of the very high 

 exhaustions needed, the constants for the computations of the absolute 

 nucleations would in any case be lacking. It is a matter of convenience, 

 however, to compute the data at the high exhaustion as if the conditions 

 met with at the low exhaustion were indefinitely applicable, and this is 

 the meaning to be given to n, the number of nuclei per cubic centimeter, 

 in the present paper. Moreover, n refers to the nucleation left in the 

 exhausted fog chamber, supposing that the nuclei are restored to the gas 

 faster than they can be withdrawn by exhaustion or that the nucleation 

 encountered is fixed for any definite environment. Otherwise n (to be 

 multiplied by the volume expansion) would be very much larger. 



The carbon dioxide used was generated from calc spar and hydro- 

 chloric acid. The gas was eventually passed through a solution of sodic 

 hydrocarbonate, a long tube of dry bicarbonate of soda, a solution of 

 silver nitrate, and a calcium chloride drying tube. Then it entered a 

 filter (2 feet long), from which it was conveyed very slowly into the fog 

 chamber. Coal gas taken from a gas pipe was treated in the same way. 



68. Data for carbon dioxide. In table 42, dp shows the drop of pres- 

 sure on exhaustion, 5/30 (approximately) the angular diameters of the 

 coronas when the eye is at 30 cm. in front and the source of light 250 

 cm. behind the fog chamber. The meaning of the other data is obvious, 

 n being the nucleation. 



*Phys. Review, xxiii, pp. 31-36, 1906. 



105 



