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composition of these bodies, and the manner in 
which they are procured. 
1. Gum is a substance which exudes from certain 
trees ; it appears in the form of a thick fluid, but 
soon hardens in the air, and becomes solid : when 
it is white, or yellowish white, more or less trans- 
parent, and somewhat brittle, its specific gravity 
varies from 1300 to 1490. 
There is a great variety of gums, but the best 
known are gum arabic, gum Senegal, gum traga- 
canth, and the gum of the plum or cherry tree. 
Gum is soluble in water, but not soluble in spirits 
of wine. If a solution of gum be made in water, 
and spirits of wine or alcohol be added to it, the 
gum separates in the form of white flakes. Gum 
can be made to inflame only with difficulty ; much 
moisture is given off in the process, which takes 
place with a dark smoke and feeble blue flame, 
and a coal remains. 
The characteristic properties of gum are its 
easy solubility in water, and its insolubility in alco- 
hol. Different chemical substances have been 
proposed for ascertaining the presence of gum, but 
there is reason to believe that few of them afford 
accurate results ; and most of them, (particularly 
the metallic salts,) which produce changes in 
solutions of gum, may be conceived to act rather 
upon some saline compounds existing in the gum, 
than upon the pure vegetable principle. 
Mucilage must be considered as a variety of 
gum ; it agrees with it in its most important pro- 
perties, but seems to have less attraction for water. 
— According to Hermbstadt, when gum and muci- 
