No. 614] THE USES OF INSECT GALLS 



163 



other astringent than an infusion of gall-nuts could be 

 used in the dyeing bath, as too large a quantity of any 

 other material would be necessary to obtain the same 

 results. 



Bancroft, however, in his 4 'Philosophy of Permanent 

 Color," 1813, opposed the idea that the astri Mgency was 

 the important property of the gall-nut and set forth the 

 idea that it should be considered merely as a coloring 

 matter. In defense of his theory he showed that tannin 

 procured from different vegetable matter and combined 

 with iron will not produce black, and gallic acid alone will 

 not blacken solutions of iron, while either tannin or gallic 

 acid from galls combined with iron forms a black dye 

 or ink. 



At the present time both these theories are known to be 

 true for the Aleppo gall may be used as a fixing agent in 

 dyeing or may be used as the basis of a good black dye. 

 As a dye its use appears to be confined to the dyeing of 

 leather and of sealskin fur. 



In the dyeing of leathers and skins the Aleppo gall is 

 used in small quantities with other dyeing materials to 

 obtain the best and most permanent black. That the suc- 

 cessful dyeing of leathers, however, is not dependent en- 

 tirely upon a good dye is evident from the following state- 

 ment on leather dyeing by Bennett, ' 1 Manufacture of 

 Leather," 1909: 



The absorption of the dye by the fiber has been considered a ease of 

 ehemiea] action, of physical action and even as a case of "solid solu- 

 tion," but it is highly probable that more than one type of action comes 

 into play and that possibly all these theories may be true to a certain 



determining factor is the formation of color lakes with the tanniifon the 

 fiber. The tannins are of an acid nature and fix the basic dyes with 



much less readily than the acid dyes, so it is clear that the nature of "the 

 tannage has considerable influence in the matter. 



For the dressing and dyeing of sealskin furs, large 

 quantities of the Aleppo galls were formerly shipped to 



