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Gums
Gum Arabic, or Gum Acacia, comes mainly through Aden and Bombay.It is a true gum, derived from several of the acacias. It is known on the market under various names, sometimes indicative of quality or merely of origin.
Thus. there are;
Picked Turkey,
White Sennaar,
Gum Senegal,
Soudan or Suakim gum (second quality),
Mogador gum,
Brown Barbary,
Cape gum,
Indian gum,
Wattle gum (from Australia).
These vary partly as regards their adhesive qualities, more especially as regards colour.
(Clear or cloudy, water white to light brown.)
All dissolve in water, the best qualities taking up one and a half times their weight of water, forming a thick mucilage.
They are not soluble in alcohol; if this be added to a water solution precipitation takes place; if subacetate of lead is added a white opaque jelly results.
Alumina sulphate thickens the mucilage and adds to its adhesive properties.
Acacia spinosa produces the gum Siris of India.
Gum Ghatti is also from an acacia, but unlike the others is only formed into a jelly on being soaked in water.
Gum Tragacanth, or Gum Dragon, is an exudation from the astragalus shrubs of Asia Minor. It is transparent, soluble in water, and used both to produce water gums and for mixing in translucent colourless varnishes. It comes on the market in: ( I) leaf form, (2) vermicelli.
Dextrine, or British Gum, is manufactured by heating starch for several hours to between 2120 to 27SoC., and adding an acid.
"White" dextrine is of a pale yellow; " Canary" a bright to dark yellow;
inferior qualities brown.
It has a sweetish taste, is soluble in water, and has excellent adhesive qualities.
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