1885.] A. Pedler — Corrosion of Lead Linings of Indian Tea Ohests, 169 



The action of these woods on lead was tested in another way by 

 macerating samples of the splintered wood in water, evaporating till a 

 fairly concentrated extract of the soluble principles of the wood was 

 obtained, and then painting the surface of some tea-lead with the extract, 

 and exposing the lead so prepared to the action of moist carbonic acid 

 and air. 



The lead scarcely acted on. 



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A small amount of lead carbonate formed. 

 Slight amount of lead carbonate formed. 



No. 1 sample, 



No. 2 



j> 



No. 3 



1) 



No. 4 



>> 



No. 5 



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No. 6 



ft 



No. 7 



»> 



No. 8 



>> 



No. 9 



j> 



No. 10 



1) 



Practically no action on the lead. 



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Slight amount of lead carbonate formed. 



The amount of action in this set of ten experiments, and also in the 

 previous set of ten experiments with the distillates in steam of these 

 woods, was in all cases comparatively slight, and it was not to be compar- 

 ed in extent or in nature, to the action which the same woods had pro- 

 duced originally on the tea-leads which had been packed between them ; 

 and the conclusion which naturally suggests itself from this is, that the 

 cause of corrosion does not pre-exist in the wood in the condition of a 

 volatile substance, and that it is not present to any large extent in the 

 solution obtained by extracting the wood with water. 



Taking these results then in connection with those previously detailed, 

 it is clear that the corroding substance, whatever it may be, must be 

 formed gradually in the wood, and that the formation is connected with 

 the continued presence of moisture, or with the wood being in a damp 

 and unseasoned state, and also that the active agent in the corrosion is a 

 volatile body. 



The next step in the investigation of the subject is clearly to trace 

 out the active agents which induce the corrosion of the tea-lead, and, in 

 order to do this, I thought it desirable to observe the action of tea- 

 lead when placed in contact with vapours of various classes of substances 

 which might induce corrosion, or which under certain circumstances 

 might be produced from wood, and in the presence of moist air and car- 

 bonic acid also induce corrosion. My reason of course for working only 

 with the vapours of these substances was that in all the cases of corro- 

 sion I had examined there were always parts of the corroded lead which 

 were not in actual contact with the wood, and which therefore could 



