Electrification associated with Dust-Clouds. 487 



predominate ? With this idea in view, groups of salts were 

 studied in which the acid was "strong" or "weak" rela- 

 tively to the base, and Table V. shows the results obtained 

 with the carbonates. Carbonic acid may be regarded as a 

 "weak" acid, so that the electrification due to the base 

 might be expected to be dominant. 



Table Y. 



Carbonate. 



Charge. 



Carbonate. 



Charge. 



Ammonium 



_ ? 



4- 

 4- 



Iron 



1 1 1 1 1 1 1 1 4 





Lead 



Manganese 



Beryllium 



Bismuth 



Cadmium 



Lithium 



Calcium 



Potassium 



Strontium 



Cobalt 



Chromium 



Copper 



Zinc 







There are three exceptions occurring in this table, which 

 may have been due to contamination, as it seems anomalous 

 that chromium and iron carbonates should differ from the 

 carbonates of cobalt, manganese, and nickel. 



Nitric and hydrochloric are " strong " acids, and here it 

 might be expected that the electrification produced would 

 be positive, if the reasoning applied to the carbonates was 

 correct, and this is substantiated by Table VI. Even aniline 

 chloride obeys the rule. 



Table VI. 



Salt. 



Charge. 



Salt. 



Charge. 



Ammonium chloride ... 

 Barium ,, 

 Calcium „ 

 Copper „ 

 Lead ,, 

 Mercurous ,, 

 Mercuric ,, 

 Aniline ,, 



4- 



: 



4- 

 + 

 4- 

 4- 

 4- 



Sodium ., 



Barium nitrate 



4- 



4- 



+ 

 ■f 

 4- 

 + 

 + 



Bismuth ,, 



Lead ,, 



Potassium ,, 





