228 
BRITISH PHARMACEUTICAL CONFERENCE. 
tlie reactions are not so distinct as with 25 per cent., but I consider them 
usually sufficient to decide the case. 
I believe that when the adulteration of olive oil is so prevalent as at the pre¬ 
sent time it is the interest of members of the drug trade to use this test them¬ 
selves, and also, in many cases, to inform large consumers how easily it is applied. 
TANNIN IN BRITISH GALLS. 
BY WILLIAM JUDD, F.C.S. 
Having noticed for some three or four years past the large quantity of 
galls on the oaks in this neighbourhood, the question naturally occurred, 
Could not these galls be turned to some practical account ? Wlien, there¬ 
fore, this subject was proposed for investigation by the British Pharmaceu¬ 
tical Conference, I gladly undertook to do what I could to set the matter at 
rest. Great differences of opinion appear to exist as to the value of these 
galls, and those who have examined them have arrived at very various con¬ 
clusions, This may have been partly attributable to the different ages of the 
galls in which the tannin was estimated. 
The questions proposed are, “ What is the quantity of tannin in English 
galls (Cynijps Quercus-petioli) at different stages of their growth P Can they, 
at either ot these periods, be employed economically as a substitute for the 
nut-galls of commerce ?” 
p-'ke reply to the second question must obviously depend on the results ob¬ 
tained in investigating the first. 
M y fiist aim was to ascertain the most trustworthy and simple process for 
estimating the quantity of tannin present. The gelatine process being open 
to many objections, X endeavoured to substitute some other. The plan re- 
commended by Mr. Marriage in Pharmaceutical Journal, vol. iii. p. 509, 
with ammonio-sulphate of copper, was inadmissible on account of the dense 
colour of the fluid obtained by percolating or macerating the galls. The 
gallo-tannates of lead and antimony are said by Miller to be insoluble, and I 
attempted to found a process on this fact, but without success. These com¬ 
pounds are not so insoluble as stated. Many other plans were tried, but 
with them all there w r as some difficulty or obstacle that rendered the process 
useless. I was obliged, at last, to adopt the gelatine process, modified by the 
addition of alum, as suggested by Muller. 
It is unnecessary to detail all the experiments; suffice it to say, the fol¬ 
lowing results are the mean of several trials, the galls also being exhausted in 
various ways:— 
I. I fiist examined a sample of old galls, which had hung on the trees till 
Christmas, of course perforated by the escape of the fly. They were found 
to contain an average of 15*97 per cent, of tannin. 
II. Galls gathered when mature (in the month of August), not perforated. 
Ihese were found to contain 17‘65 per cent, of tannin. 
III. Galls gathered when about half developed and dried, producing a more 
dense and shrivelled gall, Iliese contained 13'4 per cent, of tannin. It 
appears from this that the mature galls, gathered before the escape of the fly, 
contain, as might have been expected, the largest quantity of tannin. 
V\ ith these data we may turn to the second question, “ Can they, at either 
of these periods, be empk^ed economically as a substitute for the nut-o-alls 
of commerce r 
lhe quantity of tannin contained in Aleppo galls, as stated by various 
authors, ranges from 30 to G5 per cent., which is obviously much more than 
