SOLUTION AL NUCLEI IN GENERAL. 139 



tion partially evaporated. Clearly the water nucleus is always larger 

 than the original nucleus which it holds in solution. 



Phenomena of the present kind may be examined by identically 

 agitating solutions of different bodies in different solvents and of differ- 

 ent strengths, beginning with the pure solvent. This may be water 

 or any other volatile liquid. The number of nuclei obtained, ccet. 

 par., varies both with the solvent and the solute. Thus on shaking 

 i per cent solutions identically and computing the number of nuclei, 

 IV, from the coronas observed in each case the following data were 

 found: Pure water, A^ = = 130 ; organic bodies dissolved in water (su- 

 crose, glucose, glycerin, urea, etc.), N-=6oo ; mineral salts dissolved 

 in water (nitrates, chlorides, sulphates, etc.), A 7 " 1,300; naphthalene 

 dissolved in benzol, N ==3,500 ; paraffin in benzol, A^= 5,000. A 

 definite demarcation of groups is thus apparent, but it is difficult to 

 even conjecture an explanation. 



If the solvent is pure, the nuclei produced by shaking are exces- 

 sively fleeting, a result attributable to their relatively small size. As 

 the concentration increases for a given solvent, persistence increases 

 with the number of nuclei produced. 



If the absorption per second takes place ct the walls of the vessel as 

 the first power of the number of nuclei present, the following constants 

 (k) show the character of the phenomena: 



Pure water k = 5-10 



Inorganic saline solutions i percent = 0.05 



o.oi percent & 0.08 



o.oooi percent k = z 



Neutral organic solutes in water, i percent = 0.2 



o.oi percent 7e=o.6 



Neutral liquid organic solutes in water. i per cent k = i.2 



o.oi percent = 2.4 



Solid hydrocarbons in liquid hydrocarbons, i percent k = o.o2 to 0.04 



When the solvent is a hydrocarbon, etc., the fog particles are rela- 

 tively large as compared with the water particles (cat. par.). Hence the 

 coronas remain normal (white-centered and showing the usual diffrac- 

 tion pattern) even when the nuclei are present in millions per cubic 

 centimeter. These coronas, moreover, are intensely brilliant, and 

 but for the difficulty in keeping the heavy vapors saturated, they 

 would offer exceptionally good conditions for the measurement of 

 nucleations. Again, the exhaustion method is available for investigat- 

 ing the diffusion of the heavy vapors into nucleated air. Finally, 

 sulphuric-acid nuclei, sulphur and sulphide nuclei (oxidizable to sul- 

 phates) are probably a special class of water nuclei which are stable 

 because they contain an intensely hygroscopic solute. 



