on the Action of Water and Air on Lead, 89 



e. gr. the removing the rods of lead from the bottle is suffi- 

 cient. I cannot say from experiment whether this effect is 

 determined by the contact of the carbonic acid in the atmo- 

 sphere, and that the substance deposited is identical with 

 the white crystalline body already described, or from some 

 other cause, but am more inclined to think it should be re- 

 ferred to the agitation of the liquid, which causes crystalliza- 

 tion to take place in a nearly saturated solution. 



In an experiment in which fresh distilled water was agitated 

 with pure oxygen gas, clean slips of lead being introduced 

 into it, and the phial closed by a perforated cork, through 

 which an open tube passed filled with fragments of slacked 

 lime, the liquid when examined after three weeks appeared 

 by the action of tests the strongest aqueous solution of 

 lead I had obtained ; but the white deposit at the bottom of 

 the phial was much scantier and less bulky, and had none 

 of the crystalline character previously observed. Whether 

 moist or after drying in vacuo, it did not present the 

 slightest appearance of effervescence when dissolved by di- 

 lute nitric acid. 



27. I have before said that Dr. Christison has stated, as the 

 results of his experiments, that the lead dissolved by water is 

 in the state of carbonate. But the following experiments, I 

 think, show, that, in my method of experimenting at least, such 

 is not the case, and also that the carbonate is a much less so- 

 luble substance than the oxide or hydrated oxide. 



28. A solution of carbonic acid was prepared by passing 

 the gas evolved from calcareous spar and very dilute nitric 

 acid into an air holder, and from that into distilled water, con- 

 tained in a large two-necked bottle, where the gas could be 

 agitated with the water under moderate pressure. In this 

 way a solution was obtained free from any other acid, and 

 which, by boiling, gave off about two thirds of its volume of 

 carbonic acid gas. 



When this solution of carbonic acid was poured into a so- 

 lution of lead in distilled water, obtained as before (8.), a pre- 

 cipitate took place, which, however, was redissolved b} r consi- 

 derable excess of the solution of carbonic acid. In this, again, 

 solution of bicarbonate of potash caused a cloudiness. 



29. Into the reserved portion of the solution from the 3rd 

 experiment (par. 22.) = 2500 grains by measure, a current 

 of carbonic acid, evolved from dilute nitric acid and calcareous 

 spar, was passed : this immediately caused a cloudiness, and 

 when the precipitate had subsided, a portion of the clear 

 liquid was tested by sulphuretted hydrogen, which gave a very 



Third Scries. Vol. 5. No. 26. Aug. 1834. N 



