THE SCIENTIFIC ASPECTS OF TANNING. 8^ 



quantity, yet owing to the inertness, not to say rapacity of the 

 Turkish Government, 30 to 35,000 tons is all that is raised on the 

 average of many years. A good sample of Valonia gives 34 P.C. 

 Tannin. It imparts great firmness and weight to the leather, and 

 in the process of tanning deposits a considerable amount of what 

 is technically known as " Bloom." This deposit was considered 

 essential to all good leather, and leather minus Bloom, stood but a 

 poor chance in the market. Its exact nomenclature is, we believe, 

 doubtful, though Parnell speaks of it as Ellagic acid, of which 

 according to Fownes, one molecule contains Ch, Hg, Og,. Light 

 and air are essential to its production, which would lead us to infer 

 that it was the result of a process of oxidation of the strong 

 liquors which contain tannic acid in excess: weak liquors yielding 

 no Bloom. 



Next in importance stands Myrabolans. The fruit of the 

 " Terminalia CherhuW^ closely allied to the Myrtle. Our 

 dependencies in" Bengal and Bombay furnish us with considerable 

 quantities. Comparatively a new arrival, as in 1867 we imported 

 3,000 tons J in 1874, 8,714 tons. The fruit contains a kernel or 

 stone possessing no tanning properties, Myrabolans give from 

 twenty to forty per cent, tannic acid. Leather tanned exclusively 

 with it has a yellow color, but is soft and mellow in working. It 

 deposits a large quantity of Bloom 3 also acetic acid is found in 

 the inferior parcels, some samples which we have analysed, having 

 apparently been heated on the voyage, gave us another kind of 

 tannic acid, giving similar results with all the reagents, as the 

 tannic acid of Oak Bark, but insoluble in cold water. We have 

 never had this fact previously noticed. Dr. Stenhouse has dis- 

 covered a large amount of gallic acid in Myrabolams. Notice here, 

 by the way, that Valonia, Mijraholans, and D. Diri, of which we 

 have next to speak, are prone to a chemical decomposition. During 

 the process, the tannic becomes changed into gallic acid. Tannic 

 acid, according to Fownes, when boiled with acids assimilates 

 water, and splits up into gallic acid and glucose ; 



C 7 H22 0„ + 4 OH^ = 3 C7 He O5 + Ce H,2 O 



