432 
KEl'OKT OF CHEMICAL LABOKATOKY 
gum from natural cracks or fissures in the bark (natural or wady gum), but the 
evidence is too limited to be anything more than suggestive. 
Viscosity of 
*20 per cent, 
solution 
Young 
Tiiees 
Old Trees 
Young Trees in 
Valley Geneina 
From tapped 
- Natural ” 
P'rom tapped 
Natural ” 
From tapped 
“ Natural ” 
trees 
exudation 
trees 
exudation 
trees 
exudation 
Dctcrmiiiod, March, ’07 
83-5° 
, 40*5^ 
77*5'’ 
31° 
i 122-.5° 
ropy 
Nuv. ’07 
33-0“ 
4U-U' 
4ir.T' 
(slightly 
; rupy) 
5.‘)“ 
sohiti(»ii 
35*3" 
(no trace of (no trace of 
ropiness) ropiness) 
Acidity (inilligranis KHO required ‘i'UO 
to neutralise one gramme) ! 
2‘00 2-8U 
2-85 23.5 ' 271 ) 
Ash 
3-85 
s-oo 
3*05 
3*15 
3*05 
3-25 
.Summary of 
results 
Tlie colour of the gum of tapped trees is almost invariably lighter than that of 
“natural” exudations. 
Up to the present the observations which have been made indicate that great 
reduction in viscosity, as the result of storage, takes place only in the case of the gum from 
early collections, and that a mift gum which yields a solution of high viscosity will alter 
materially and quickly on keeping. 
The results of the examination of the gums from the several geneinas in the vicinity of 
Taiara, which have been tabulated on ixiyea 4‘24 42S, may be summarised as follows :— 
1. Clum of the earliest exudations, after tajiping, is usually less soluble. This is 
especially the case with gum from old trees. 
2. Storage results in a change by which the above gum becomes quite soluble. 
3. Towards the end of the collecting season, the gum is found to become more hard 
and glassy, but in the case of the samples tested this year the hard gum did not yield a 
solution of high viscosity, as is usually the case with hard Kordofan gum. 
4. There was a fairly regular decrease iu “viscosity-strength” of the gum as the 
season advanced. 
5. Contrary to the statements made by the gum collectors, and which appeared to be 
supported by the results of examination of several samples, the gum from older trees 
usually exhibits a slightly higher strength than that from younger trees. At the same 
time no hard, strong gum was found in any of the above collections. 
The explanation of the absence of the stronger gum from these samples may be ;— 
{a) That by reason of the local conditions as to soil, height of water-table, etc., none 
of this variety is ever exuded near Taiara. 
(/)) That it is exuded only when tapping is jierformed immediately after the rains have 
ceased. ft was intended that this should be done in October, 1907, but, through a 
misunderstanding, the instructions were not carried out. 
(c) That it is exuded only in certain years under appropriate conditions of temperature 
and rainfall. 
Gum dealers state that hard, strong gum comes to them in far larger quantity during 
the months of November and December, and a sample obtained from one of them, known 
to have been collected towards the end of 1907, was found to consist largely of this 
variety of gum. 
This question will be studied in the collections which it has been arranged to have 
made during the coming season. 
