THE STKUCTiniE OF THE NUCLEUS. 



85 



Even with air nuclei, therefoi'e, the first corona is a canipaiiulate form, indicat- 

 ing strongly graded nucleation. After continued i)i'eci[)itati()n tiie grading is wiped 

 out, and the coronas become nearly regular until they vanish. 



The nuclei produced by shaking toluol were found to persist in experiments 

 lasting 10 minutes, 150 minutes, and 240 minutes, resi)ectively, with but negligible 

 diminution of brilliancy in the coronas. 



23. Carbon disnlphide. — In the given apparatus, in which rubber sto^jpers 

 and tubes made an essential part, it was impossible to preserve this regent free fi'oni 

 impurities in solution, even when the liquid is apparently kept in contact with glass 

 only. To do this it would have been necessary to consti'uct all parts of the appa- 

 ratus of slass, which did not seem to be wan-anted, and \vhich would have made it 

 much less suitable for the general purposes of the present pai'agraph. Apart from 

 this, the decomposition which the liquid itself undergoes in the light or on con- 

 tinued evaporation, seems to be cpncerued, and any rubber tube through which the 

 vapor has passed becomes nuclei-producing. With this reservation, carbon disnl- 

 phide produces nuclei spontaneously and in abundance, a [)roperty which makes an 

 interesting special contribution to the subject. 



24. Conmas. — The removal of air nuclei is already peculiai', and is pi'actically 

 complete in a few^ exhaustions. Thus I found successively, 



Exhaustion No., i 2 



Corona, Full, y=:. 58 Semi-corona. 



The first corona is of the ordinary tyi>e and (luite possibly due to spontaneous 

 nuclei. The second is semi-circular, and the remaining coi'onas mere colored veils 

 at the bottom of the vessel. On adding an excess of sulphur nuclei from the flame 

 the display is again insignificant and curtailed to mere fogs, as the following table 

 shows. 



345 

 Coronas nearly absent. 



TABLE 10.— PROPERTIES OF SULPHUR NUCLEI IN VAPOR OF CARBON 

 BISULPHIDE. EXHAUSTION, 76-58 cm. 



Hence, sulphur nuclei are ineffective, or have the usual property of brooding over 

 the surface particularly pronounced. Thence they very slowly diffuse upAvard. 



The following table evidences an entirely similar behavior in relation to punk 

 nuclei. 



