1885.] A. Pedler — Corrosion of Lead Linings of Indian Tea Chests. 173 



Evidently then the action which has taken place in the case of these 

 woods in contact with the tea-lead has been identical with that previous- 

 ly described as the Dutch method of making white lead. Acetic acid was 

 present in minute quantity, moist air and carbonic acid have also been 

 present at a comparatively high temperature, and thus all the conditions 

 were favourable for the production of white lead. 



The conclusion, then, at which I arrived was that the corrosion was 

 produced by the unseasoned, or moistened wood, and that acetic acid was 

 the active agent in the corrosion. In order to further test the point, I 

 made extracts from the various samples of wood numbered 1, 2, 3, 4, 5, 6, 

 7, 8, 9, and 10, and distilled these extracts with dilute sulphuric acid. In 

 all cases a distillate of distinctly acid and acetous smell was obtained, 

 evidently showing the presence of small quantities of acetic or some 

 analogous acid in combination in these woods. 



The final point which then remains to be cleared up is the origin of 

 the acetic acid from the wood, for, as previously pointed out, it evidently 

 does not exist in the first instance ready formed in the wood, but is pro- 

 duced by some secondary action. Dr. Wigner in the publication previ- 

 ously referred to put forward a very probable theory. He remarks 

 " The sap of wood invariably contains sugar. The quantity is small, but 

 still measurable. This sugar is in every case, which has come under my 

 knowledge, a fermentable sugar, and the first result of the fermentation 

 is in most cases alcohol. Fermentation being carried a step further free 

 acetic acid is the natural result. With the formation of acetic acid 

 carbonic acid is also formed ... Transferring this from a theoretical to a 

 practical case : A wood containing sap which was more than usually 

 saturated with sugar, and exposed to a moist heat, would ferment more 

 readily, would produce a larger quantity of alcohol, would consequently 

 produce a larger quantity of acetic acid, and would therefore, by infer- 

 ence, derived from practical work, produce a larger amount of carbonic 

 acid, and thence of white lead. These effects would be produced mainly, 

 if not entirely, upon the surface of the wood, and one of these surfaces 

 would be in contact with the metallic lead which forms the lining of the 

 case. Now let us see what would take place. The lead lining would be 

 exactly in the same condition as the lead in a leadstack which was being 

 worked by the Dutch process. Acetic acid, carbonic acid, and moisture 

 would all be present. There would be a reasonable and probably, in 

 accordance with practice, a very proper degree of heat, and the lead and 

 wood would be in contact ; and it seems the most natural thing in the 

 world to assume that, as the result, acetate of lead would be formed by 

 the direct action of the acetic acid. Carbonate and hydrate of lead 

 would be formed from this by the action of the carbonic acid and the 



