442 
UKTOllT OF CHEMICAL LAHOUATOKY 
Sugar in 
gums 
Hashab 
gum 
It may be mentioned that all the gums examined contained a small quantity of reducing 
sugar, varying in Hashab gum from a mere trace up to about 0-15 per cent. This does not 
form an essential part of the gum, and may be readily removed by dialysis. The sugar is 
most probably derived from the sap of the tree, some of which would adhere to the gum 
on drying. The nitrogenous matter in the gums examined is also very small in quantity, 
and quite independent of the strength of the gum. It also is probably derived from the sap. 
Ex.4min.\tion of H.\sh.\b Gun 
The pentoses were estimated in one gramme of gum by distilling with 12 per cent, 
hydrochloric acid, and precipitating the furfurol produced with phloroglucin. The method 
followed was that described by Krober and Rimbach.^ From the precipitate the pentoses 
were calculated as arabinose. I found that this method was more convenient, and gave 
more concordant results wuth the same sample of gum, than the method of precipitating the 
furfurol with phenylhydraziue. 
I at first attempted to estimate the galactan portion of the gum molecule by oxidising 
the gum with dilute nitric acid, filtering and weighing the mucic acid.- It was very 
difficult, however, to get two determinations of galactan in the same sample of gum to 
give results sufficiently nearly equal, though I found this method very useful in giving an 
approximate idea of the relative proportions of pentoses and hexoses produced on 
hydrolysis. 
The total amount of reducing sugars was estimated by boiling a four per cent, solution 
of gum in five per cent, sulphuric acid for five hours under a reflux condenser. The 
reduction was then determined in five cubic centimetres after neutralisation, by boiling 
wuth a slight excess of Fehling’s solution. The cuprous oxide was filtered off, washed and 
ignited. It w'as found that hydrolysis was complete in nearly every case after four hours’ 
boiling. 
The most important results obtained by this method of examination are shown 
below :— 
Source of Gum 
Phloroglucide 
from I gramme 
gum 
Per cent, 
of 
arabinose 
Grammes CuO 
from I gramme 
gum after 
hydrolysis 
Per cent, 
of 
hexoses 
3b trees. Ist cullectiou 
0-3184 grms. 
3,5-37 
2-005 
52-22 
„ . 
0-.3191 
35- 45 
2-025 
53-04 
3rd „ . 
(i-siya „ 
35-48 
2-024 
52-94 
„ 4tli „ . 
U-31.03 „ 
35-02 
2-004 
52-54 
,. .'rtli „ . 
6-3175 ,, 
35-27 
1-973 
50-88 
,, 6th „ . 
0.3176 „ 
35-29 
1-966 
50-52 
Kordofan, Decicmbor, 1'JII7 ... ... . 
0-3148 ,, 
34-97 
1-980 
51-.54 
Senegal, <jrossc blanch' 
0-3113 „ 
34-59 
1-975 
51-72 
Souogiil, has dll fleuoc, 1908 ... . 
0-3030 
33-GG 
1-985 
53-17 
Kordufan hard glassy guni ... 
0..3U94 ,, 
34.-37 
1-955 
51-04 
Kordofan ‘'bleached” gum 
0..30-20 
33-52 
1-965 
52-35 
Kordofan ropy gum... 
0-319,5 
3.5-49 
1-985 
.51-18 
rjt ii,d. j . iiinftit. fti nilty v |J. 
- Allau, “ Cuuimercial Organic Analysis 
