Observations on Squamosis and Exanthema of the Citrus. 123 
QUALITATIVE REACTIONS OF PRUNUS AND C/TRUS GUMS. 
Reagent. _ Lemon gum. Cherry gum. Plum gum. 
Hydrochloric acid and) |, sontred.t saci wt 
: eae an bright red, then dark pp.|bright red, then dark pp.|bright red, then dark pp, 
Alcohol 9 per cent. excess .. white pp. white curdy pp. white pp. 
Acetic acid, dil... . —- . —— ——-. 
Glacial acetic acid, excess white pp. . -white pp. white pp. 
Nitricacid . . solution coloured yellow|solution coloured yellow/solution coloured yellow! 
»  », and ammonia §| colour heightened tea colour heightened 
Millon’s reagent . . . solution deep red solution yellowish solution reddened 
yellow pp. 
Tannic and acetic acids . ——_— 
Sodium molybdate. . . 
Potassium-mercuric iodide —_— SSS —_——-. 
P prion aaa sul- cloudy white pp. large curdy pp. liquid cloudy 
Sodium phosphomolybdate a solution thickened — 
Sodium phosphotungstate —_——- white pp. trace of reaction 
Mercuric nitrate and ni- ) | fine pp. remaining in fine pp. remaining in |. 
tric acid suspension suspension 
Adamkiewicz reaction . ———— a ome 
Biuret test . . 1... 
Lead acetate and sodium 
ee bright yell then | bright yellow, tl bright yellow then dark 
: é rig. ellow, en right yellow, then right yellow then dar 
Hydrochloric acid, . siege amber dark brown pen slight pp. 
Ferric chloride . . . .| red gelatinous pp. es —— 
Fehling solution . . . ——— = reaction doubtful 
Lead acetate. . . .. milky, slight pp. See Ss milky 
Ammoniacal lead acetate |abundantgelatinous pp.|abundant gelatinous pp.|abundant gelatinous pp.) 
Basic lead acetate,. . .| fine curdy pp. = fine gelatinous pp. 
Calcium hydrate . . . — ete —- 
Potassium hydrate. . . ——— sol, slightly thickened |. oa 
Sodium hydrate. . . . sol. thickened sol. thickened | sol. thickened 
very slight fine pp. very slight fine pp. very slight fine pp. 
Barium hydrate . . remaining in sol. as | temaining in sol. as | remaining in sol. as . 
a faint cloud. , rie ier i ‘ a faint cloud 
ss sol. thickened, faint | S04. thickened, sig sol. thickened, faint 
Aluminium hydrate . . aloud indefinite pp. pres 
Sodium borate . . . sol. thickened sol. thickened sol. thickened 
Copper sulphate . } very slight fine pp. 
remaining in suspension 
The gums of Prunus and Citrus I have found to be soluble in water, 
A 6 per cent. solution of cherry gum is very thick, but the gum dissolves 
with shaking within twelve hours at this concentration. The lemon and 
plum gums dissolve much more readily than the cherry gum, and at the same 
concentration as the latter form a less viscous solution. All the gums 
contain nitrogenous matter, probably in variable amount. 
4. TECHNIQUE. 
In our study of the gums of Prunus and Citrus we found that they 
are soluble in water, from which they are precipitated out by strong alcohol, 
or an excess of glacial acetic acid, In preserving material for examination 
it was, therefore, quite evident that alcohol and acetic acid mixtures, or 
