INVESTIGATION OF 1905. 11 



of tannin as the average adulterated samples that is, approximately 

 27 per cent. The figures, therefore, indicate an average adulteration 

 of 30 per cent of lentiscus, which is possibly below the actual practice, 

 as high-grade sumacs are more likely to be adulterated than the lower 

 grades. Several of the samples, however, contain so little tannin 

 that it is evident that either an exceptionally low grade of sumac was 

 used or that lentiscus was almost entirely substituted. 



Ten samples were marked as containing lentiscus. In two cases the 

 examination proved the sample to be pure sumac. In no case was 

 more than a 25 per cent adulteration admitted. The average tannin 

 content of the six admittedly adulterated samples is 27.5 per cent, 

 practically identical with the average of all the adulterated samples. 



If the general statement that the "feminella" sumac contains less 

 than 25 per cent of tannin is accepted, it would appear that none of 

 the adulterated samples was plain-grown sumac. As this classifica- 

 tion seems to be based solely on the tannin content, it may be ignored 

 except in so far as it is an expression of the agricultural fact that 

 sumac grown on the high ground contains more tannin than that 

 grown in the valleys. 



Leather tanned with sumacs adulterated with lentiscus is darker 

 than that tanned with pure Sicilian sumac, and the determination of 

 the color of the extracts from these samples is in harmony with this 

 fact. The darkest extract from a pure sumac contains less red color- 

 ing matter than the lightest-colored extract from an adulterated 

 sample, while the extracts from the samples of lentiscus contained 

 several times as much coloring matter as the darkest pure sumac 

 extract. 



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