576 REPORT— 1902. 



The following Papers were read : — 



1. On the Corrosion of Copper hi/ Sea-vater, and on the Detection of 

 Traces of Impurity in the Commercial Metal. JJy Professor E. A. 

 Lktts, Ph.D. 



2. On Experiments to Ascertain the Amount of Carbotiic Anhi/dride 

 absorbed from the Sea-tcater by Air. Jhj Professor E. A. Letts, Ph.D., 

 and W. Caldwell, B.A. 



3. The Action of Distilled Water upon Ijcad. 

 P)y Professor Frank Clowes, D.Sc 



Wlien lead is placed in contact witli ordinary distilled water chemical action 

 hecnmes evident by the formation of a white deposit which contains lead, and 

 lead is also found in solution by chemical tests. 



The lead appears to exist in solution in the form of hydroxide, since it is 

 removed by passing the liquid through tilter-paper : this hxatiou by cellulose of 

 the dissolved hydroxide is one of the marked properties of the hydroxide. The 

 hydroxide is readily removed from the cellulose by dilute acetic acid. 



An examination of the white deposit proved that it was a hydroxycarbonate 

 coutaioiug three molecules of carbonate to one of hydroxide. 



It would be inferred from the above facts that tlie lead is probably converted 

 into hydroxide by the action of the dissolved oxygen, and that the subsequent 

 action of the dissolved carbon dioxide converts the hydroxide into hydroxy- 

 carbonate. 



It would appear improbable that even bright lead can decompose water with 

 formation of hydroxide. But the opinion has prevailed that the action of distilled 

 water on lead is promoted by the presence of carbonic acid. 



The nature of the action of distilled water upon lead was studied by exposing 

 bright lead, both in vacuo and in an atmosphere of hydrogen, to distilled water 

 which had been freed from its dissolved gases by boiling, and then introducing 

 either oxygen alone, carbon dioxide alone, or mixtures in varying proportions of 

 oxygen with carbon dioxide. 



Bright sheet lead of great purity when exposed to boiled distilled water in 

 vacuo or in an atmosphere of hydrogen was acted upon only to an infinitesimal 

 extent (0-3 part of lead to one million parts of water). This result was probably 

 due to the impossibility of removing the last traces of oxygen, and it negatives the 

 suggestion of any direct action of water upon lead. 



AVhen the lead was exposed to the water in the presence of the different 

 artificial atmospheres, the action reached its greatest extent (0-023 part of lead 

 per 100 of water) when oxygen alone was present; with carbon dioxide the action 

 was slight (0-008 per cent.) ; with equal volumes of oxygen and carbon dioxide 

 about an equal efiect was produced ; while with eight volumes of oxygen to one 

 of carbon dioxide the extent of the action approached that due to oxygen. 



It is evident, therefore, that dissolved oxygen is the cause of the action of 

 distilled water upon lead, the subsequent action of carbon dioxide leading to pro- 

 duction of hydroxycarbonate. It is further evident that the presence of carbon 

 dioxide in any large proportion exerts an inhibitory efiect upon the action. 



AVhen sheet lead is immersed in ordinary distilled water with free exposure to 

 air, it is found that the rate of action is diminished by entire immersion as com- 

 pared with partial immersion, but that in both cases the total result produced is 

 ultimately the same. 



In the earlier stage of the above inquiry the ordinary aerated distilled water 

 was freed from its dissolved gases by being boiled in glass vessels. When this 

 water was allowed to reaerate Itself by exposure to the air, it did not regain its 

 original power of acting upou lead. This was found to be due to the iuhibitive 

 power of silicates dissolved from the glass, and the inhibitory power varied with 



