QUEENSLAND NATIVE ASTRINGENT MEDICINES. 
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gravity of 138, is very hygroscopic, and contains between 15 and 20 
per cent, of water, according to the moisture of the air. Very tough 
in the damp state, it is easily powdered if thoroughly dry. It dissolves, 
nearly entirely in cold water, and a 10 per cent, solution has a specific 
gravity of 1029. Siderophloia gum freed of 15-20 per cent, of water 
consists of no less than 42 per cent, of Eucalyptus arabin, forming the 
bulk of the gum in which the other constituents are dissolved and 
suspended, 28 per cent, of a tannin, 1*5 per cent, of gallic acid, and 
an undetermined amount of a soluble phlobaphene acting as colouring 
matter. 
(1.) The Eucalyptus arabin is not identical with the arable acid 
of the arabic gum, being much more soluble in alcohol. Acacia arabin 
is suddenly and entirely thrown out of a watery solution by alcohol, 
if only some grains of chloride of sodium or a few drops of hvdro- 
chlbric acid are added. It is not altered by this reaction, and 
dissolves readily in water after the alcohol is poured off. 
Eucalyptus arabin, in opposition to this, suddenly falls out only by the 
addition of much strong hydrochloric acid to the alcoholic solution, 
and is thrown out by degrees, and in the lapse of some hours when 
salt or diluted hydrochloric acid is added. Its chemical composition is 
altered through this process ; it becomes insoluble in water as an 
anhydrite, which we may call ** Meta-eucalyptus arabin. Boiling with 
caustic potash restores its solubility. Eucalyptus arabin is so closely 
united to the tannin and the colouring matter, that, by throwing it out, 
those substances will go down united with it, and only anhydrite of 
the whole Eucalyptus gum will be obtained by the precipitation. In 
the same manner every reagent throwing out the tannin will take 
down the Eucalypto-arabin too. Eor instance, sulphate of cinchonine 
or strychnia precipitates the whole Eucalyptus^ gutnj acetate of 
copper throws it to the bottom very suddenly, leaving tli3 clear water 
in the bottle ; whereas in a mixture of acacia arabin and tannic acid by 
the action of acetate of copper only the tannin is precipitated, being 
kept suspended in the solution of the unaltered arabin. Gelatine 
unites with the whole siderophloia gum to a mass looking very much 
like unvulcanised caoutchouc, which can be drawn out in long 
threads, as long as it is not dried up. 
On addition of common salt, acetic ether takes the tannic acid and 
a lighter Eucalyptus arabin out of a watery solution of siderophloia 
gum. The arabin then is thrown out of that by alcohol, and it can be 
obtained in a pure state by this means. As the siderophloia gum contains 
28*5 per cent, of tannic acid (see below), and as a watery 10 per cent, 
solution of siderophloia gum has a specific gravity of 1 029, we have 
only to subtract from this Hammer’s specific gravity of a 2*8 per cent, 
solution of tannin to know the specific weight of the Eucalyptus arabin 
solution: 1029 - 1012 = *017, indicating 4*2 per cent, of gum for 
the liquid, and 42 per cent, for the dry siderophloia gum. Any quick 
drying of the gum, as well as repeated dissolving and concentrating of 
the gum, is liable to alter it into metarabin, and to make it insoluble. 
In this manner old gums, contained under the bark of the tree for 
years, become only soluble by boiling them in an alkaline solution. 
By boiling a solution of siderophloia gum with hydrochloric acid the 
meta-eucalypto-arabin after some standing falls out, together with 
the soluble colouring phlobaphene, which is turned more yellow. By 
