10 BULLETIN 706, U. S. DEPARTMENT OF AGRICULTURE. 
Examination of a number of unextracted sumac samples gave: Ash, 
4 to 7.5 per cent; potassium oxid, 1.18 to 2.15 per cent. The ash of 
these samples contained from 25 to 30 per cent of potassium oxid. 
Comparison of the percentage of potassium oxid (K 2 0) in the origi- 
nal material and in the water extract, as obtained for the tannin 
analysis, shows that although the unextracted sumac contains rather 
high percentages of potassium oxid, as is to be expected, this is almost 
entirely removed on extraction. These experiments were made on 
finely ground sumac leaves and leaf stems, whereas in commercial 
practice the extraction generally is made on the unground leaves 
and stalks, and consequently is not so thorough, especially in the 
case of the large stalks, This practice of making extraction on 
the unground leaves and stalks undoubtedly accounts for the com- 
paratively high percentages of potassium oxid in the samples of 
commercially extracted stalks, analyses of which are given in Table 5. 
Except for the organic matter which it contains, extracted sumac 
has comparatively little value for the farmer. However, in sections 
where sumac is gathered, where the land is usually deficient in organic 
matter, the extracted material can be profitably hauled a mile or two, 
especially if before scattering on the land it can be mixed and rotted 
with barnyard manure. 
CAUSES OF POOR QUALITY IN SUMAC. 
Lack of care and attention to details in gathering and curing 
results in sumac of inferior quality. Undue exposure to the sun 
or any exposure to dew or rain while green; and heating and molding 
resulting from too deep layers and insufficient turning during curing, 
cause a decided darkening of the leaves and materially reduce the 
percentage of tannin. The presence of stalks and red leaves in cured 
sumac is objectionable, because they produce an undesirable color 
on leather. Furthermore, since the stalks contain only about one- 
fourth as much tannin as the leaves, their presence gives the mixture 
a lower tannin content. The presence of dirt or sand in cured sumac 
also is objectionable, for it increases the weight without increasing 
the tannin content, and leathers tanned with such sumac will darken 
because of the iron present. 
COOPERATION FOR BETTER SUMAC. 
One of the objects of this bulletin is to point out the necessity for 
helpful cooperation between gatherers, dealers, and extract makers, 
with a view to the production of higher-grade sumac and sumac 
extracts and the payment of higher prices to the gatherers for better 
sumac. This cooperation can be successfully maintained only if it 
is mutually beneficial. The initiative and success rest with the final 
buyers, the extract makers, who, by offering a bonus for "extra" 
quality sumac, can encourage the gatherers to make special efforts 
