180 
Book IV. 
Distillation 
of gum. 
Its compo 
nent parts. 
VEGETABLE SUBSTANCES. 
but does not melt ; it emits air bubbles, blackens, and 
at last, when nearly reduced to charcoal, emits a low 
blue flame. This flame appears sooner if a flaming 
substance be held just above the gum. After the gum 
is consumed, there remains a small quantity of wbite 
ashes, composed chiefly of the carbonats of lime and 
potass. 
When gum is distilled in a retort, the products are 
water impregnated with a considerable quantity of py 
ro-mucous acid or acetous acid combined with oil, a little 
empyreumatic oil, carbonic acid gas, and carbonated 
hydrogen gas. When the pyromucous acid obtained by 
this process is saturated with lime, a quantity of ammo 
nia is disengaged with which that acid had been com 
bined. The charcoal which remained in the retort leaves 
behind it, after incineration, a little lime, and phosphat 
of lime *. 
These experiments shew us that gum is composed 
chiefly of hydrogen, carbon, and oxygen, and that it 
contains also azot, lime, and phosphorus. Mr Cruick 
shank has rendered it probable that the quantity of car 
bon is greater, and the quantity of oxygen less, in gum 
than in sugar t. Fourcroy and Vauquelin inform us, 
that their experiments 
give the component parts of 
65.38 oxygen 
gum as follows.. 
23.08 carbon 
11.54 hydrogen 
100.00f 
Gum, or mucilage, 
exists most abundantly in young 
plants, and gradually disappears as they arrive at perfec 
* Cruickshank, Rollo on Diabetes.  Ibid. f Fourcroy, vii. 153.