90 PROCEEDINGS OF THE AMERICAN ACADEMY 



kaline, 'And saline solutions, — all the conditions in which Cochituate 

 water can occur, — iron, if not at first, will, after a short interval, be 

 the metal at whose expense the galvanic action will be sustained. 



" 2. The Action of Iron- Rust. — It was natural to suppose that the 

 moist iron-rust flowing from the mains into the leaden pipes might, by- 

 reduction to a lower oxide, promote the oxidation and solution of lead. 

 Bars of lead in contact with hydrated peroxide of iron, in open tubes, 

 containing Cochituate, Croton, Jamaica, Fairmount, Albany, and Troy 

 water, arranged on the 15th of May, gave, when tested on the 17th, 

 22d, and 27th of May, and 7th of June, with ferrocyanide of potas- 

 sium, no indication of protoxide. The same water in which nails were 

 immersed, tested from time to time, gave occasional evidence of the 

 presence of protoxide of iron. I placed peroxide of iron and bright 

 bars of lead in flasks of distilled and Cochituate water, and sealed them, 

 on the 7th of last June. The flasks are in my possession still, and 

 though the air was expelled only so much as boiling five minutes would 

 accomplish, the bars of lead are quite as undimmed as on the day they 

 were sealed up. It is scarcely necessary to state that the iron rust, in 

 actual service, does not come in contact with lead, but with the subox- 

 ide, or other coat.* 



" 3. The Solubility of the Suboxide of Lead. — I have been unable 

 to procure the slightest trace of lead in water deprived of its air, after 

 long contact with the suboxide of lead. Mitscherlich remarks of its in- 

 solubility. f 



" 4. The Action of Alkaline Chlorides upon Lead, in the Absence 

 of Oxygen or Atmospheric Air. — The following experiment was 

 made and several times repeated by me with graduated solutions of 

 common salt. A flask of one gill capacity, containing a quantity of 

 lead shavings, presenting an extent of surface comparatively great, was 

 one third filled with a solution of common salt. This flask w^as connect- 

 ed by a tube, bent twice at right angles, with a cup of mercury. The 

 cork, tube, and neck, at the connections, were carefully covered with 

 sealing-wax, that the flask might be air-tight. So arranged, the flask 



* Reference has been made to the experiments of Napier upon this point. He 

 made no experiments with peroxide of iron, but with neutral salts of tlie peroxide, 

 and he states distinctly that lead exposed to them a little while became coated, 

 and that action was thereafter arrested. — Loud., Edinh., and Dull. P/dlos. Mag., 

 May, 1844, pp. 365-370. 



t Lehrbuch der Cliemie, 2te Band, S. 511. 



