Part IV.] Pusan Singh: Preparation of Tannin Extracts. 15 
of the rotting of the wood (or for matter of that of the bark), is to render 
insoluble a large proportion of the bodies originally soluble. They give the 
following analysis of the sound and the rotten chestnut wood which speaks 
for itself : — 
I 
II 
Sound wood. 
Rotten wood. 
Sound wood. 
Rotten wood. 
Soluble tannin 
7*40 
2*80 
610 
3*40 
Non-tannin 
1-90 
1*10 
1-50 
100 
M oisture .... 
54*25 
6328 
53-20 
64-24 
(2) 11 te quality of water . It is well known that mineral matters 
present in natural waters, when used for extraction of tanning materials, 
have an injurious effect on the colour and percentage of tannin in the 
resulting extract, on the colour more so, when the water is alkaline or 
when it has traces of iron in it. The loss of tannin is due to the forma¬ 
tion of non-tannins and in some cases alkaline tannates. This process of 
decomposition of tannin set up bv the mineral matter does not cease after 
the extracts have been prepared in the solid form. The saline matters 
even after extraction accentuate still further the loss already incurred 
during preparation, either by actually precipitating out the tannin 
by their contact or by inducing its conversion into non-tannin. In 
any case, the consequence is that the tannin extract prepared by saline 
waters will not only show loss of tannin during the process of manufacture, 
but will continue to do so even on storing. 1 
Besides this chemical decomposition, if the concentrated water remain¬ 
ing after evaporation is at all alkaline, it will darken and deepen the red 
colour of the extract made from mangrove barks. It may be pointed 
1 See note on The transformations which are produced in the infusions of the tanning 
.material” (when extracted by saline solutions) by Ed. Nihoul and L. van de Butte 
.quoted by Messrs. Dumsney and Noyer (loc. cit., page 141) and also on “The effect of 
'the chlorides and sulphates of natural waters on the extraction of tanning substances, ” 
Bull- Assoc. Bel. des Chimistes, 1904, pages 115 to 1£3, 
332 
