OF ARTS AND SCIENCES. 



93 



" Table XXIV. — Experiments with the several Waters deprived 

 of their Organic Matter and Carbonate of Lime.* 



" It will be seen, on comparing the results of their actions with those 

 of the natural waters, that they are more protracted and vigorous, that 

 they approach more nearly the action of distilled water, and that no 

 protecting coat can be said to have formed. Three kinds of coating 

 upon lead have fallen under my notice : a bluish-gray one, which, ac- 

 cording to Winkelbleck, Mitscherlich, and others, is a simple subo.xide ; 

 a reddish one, which formed in Croton, Schuylkill, and Jamaica wa- 

 ters ; and a white one. The coat of suboxide is insoluble in water. 

 When the quantity of oxygen in solution in a given water is small, 

 this coat will be first formed. It is the only one I have seen in Croton 

 pipes less than two years in use. The addition to this coat of slimy 

 organic matter, oxide of iron, and, to some extent, carbonate of lead, 

 forms the reddish coat, the impermeable character of which, for all 

 practical purposes, is illustrated in the appearance of Croton pipe five 

 years in use, and already referred to. The white coat, it has been ob- 

 served, consists chiefly of carbonates and sulphates. 



" Solubility of Oxide of Lead. — I have already noticed the con- 

 trariety of opinion upon the solubility of the oxide of lead. I have re- 

 peated the experiments of Yorke, and confirmed his results, and am, 



* Professor Silliman, Jr., lias remarked of the alkaline reaction wliich the redis- 

 solved residues gave. The reaction of the above solutions was not observed. In 

 their extreme dilution, an alkaline reaction could not have been appreciable. 



