12 



A CONTINUOUS RECORD OF ATMOSPHERIC NUCLEATION. 



dense spontaneous fogs in the receiver were associated with selective condensa- 

 tion, then negative charges should be more rapidly dispelled. 



II. Dried emanation. — In the following experiments (table 9) the phos- 

 phorus was previously dried over calcic chloride, and then introduced into the 

 receiver from the desiccator and the shortest possible connecting tube. Dry 

 ions thtis suddenly caine in contact with water vapor, and it was supposed that 

 an unequal reduction of positive and negative ionization might ensue. The 

 ions were stored less than 5 minutes in the receiver, the shortest time practi- 

 cable. Insulation of the electrometer and parts was determined before and 

 after each measui-ement with nucleated air. 



TABLE 9.— IONIZATION OF PHOSPHORUS NUCLEI.* rfr/(f/=2.s LIT./MIN. 



TESTED AFTER 4-5 MIN. 



* Phosphorus nuclei dried over calcic chloride and conveyed by a dry current of air, before storing over water 



The residual ionization so obtained, a = .002 — .004 for positive and .002 for 

 negative charges, is smaller than heretofore, but again practically neutral. 

 Thus very dry phosphorus nuclei seem to lose their ionization quicker than if 

 placed in ordinary air; but changes of the activity of the ionizer may account 

 for the difference. 



12. Wet emanation. — For contrast, the nuclei were conveyed into the 

 receiver (table 10) in a wet ciuTcnt of air passing over phosphoiais. A U-tube 

 was used, one leg of which contained wet sponges and the other the phosphoiiis 

 grid, the damp air from the former sweeping over the latter into the receiver. 

 The ionization fotmd is distinctly greater ' than the dry air data of the last 

 table, though it does not exceed the usual values for room air. The difficulty 

 of keeping the ionizing activity constant is again involved. According to the 

 table, positive charges are more rapidly discharged than negative charges, 

 which would indicate an excess of negative ions comparable to the case of 

 water nuclei in the next chapter. , 



' American Journal of Science (4), xii, p. 327, 1901. 



