94? Capt. P. Yorke on the Action of Water and Air on Lead. 



following results, which probably also show the relative quan- 

 tities of electricity evolved. 



1. Liquid distilled water: lead and iron gave -^th of the 

 force of similar plates of zinc and copper. 



2. Liquid spring water used (4. and 5.) T Vth. The lead as 

 zinc in both these experiments. 



3. Sulphuric acid ^ a drachm, spring water 4 ounces, 

 ^Vth; the lead being as zinc. In a few minutes the 

 order was reversed ; in one instance it was reversed in 

 one minute : the lead became as copper, and the force 

 T Vth that given by copper and zinc. 



In this state lead was found to be negative even to copper. 



With a solution of potash, the lead as zinc, the force was 

 double that given by copper and zinc ; and though it di- 

 minished rapidly, no reversal took place. 



With a solution of carbonic acid in distilled water, no di- 

 vergence of the needle took place on immersion of the plates 

 of iron and lead. 



Conclusion, 



The following seem to be the principal conclusions that 

 may be derived from the preceding experiments, and from 

 some facts mentioned by other inquirers. 



When lead is immersed in distilled water containing air, 

 the lead combining with oxygen as derived from the air gives 

 rise to the formation of a hyd rated oxide, a portion of which, 

 equal to about , t \ 00 th of the weight of the water, or a little 

 more, is dissolved (8.), (22.), (25.), (28.); — that besides the lead 

 dissolved, there are formed by the same agency two solid 

 products ; the first, in order of time, a very light crystalline 

 substance, which is either a mixture of (18.), or perhaps a 

 compound of (19.), equal proportionals of hydrate and carbo- 

 nate of lead ; the second an anhydrous oxide in grey la- 

 mellar crystals, and small white dodecahedrons (8.) That this 

 second substance has crystallized from its aqueous solution 

 is shown by its deposition on the iron (12.). 



When small but variable proportions of saline substances 

 are dissolved in the water in which the lead is immersed, the 

 action just mentioned is prevented (Christison) ; the affinity of 

 water for the oxide of lead appears to be so weakened that 

 no hydrate is formed, and no solution takes place, but the 

 lead is slowly invested by oxide. 



But it appears that when exposed to a confined atmosphere 

 loaded with aqueous vapour, and especially if in contact with 

 organic hygrometric substances, it becomes encrusted by car- 

 bonate, as in the case of bullets from cartridges, mentioned 



