ON THE MANUFACTURE OP ARTIFICIAL GUM. 289 
phenomenon so often observed in evaporating viscous 
liquids, viz., their being quite still, and which I have ascer. 
tained is caused by the formation of a very thick sediment 
on the sides of the evaporating vessels. 
The liquor, when drawn off after settling, will mark 
about 10° B., and it is evaporated by raising it very slowly 
to the boiling-point ; which precaution is indispensable, for 
the perfect clarification is accelerated by checking the first 
boiling, as in refining sugar. This clarification is effected 
without any foreign agent, by the coagulation of the vege. 
table albumen contained in the malt and the linseed muci- 
lage. As scum will continue to rise to the top of the mu- 
cilaginous syrup daring the most of the time of baking, it will 
be necessary to remove it carefully ; and if the boiling is too 
much accelerated, the gum will first become thick, and 
afterwards will be coloured. When a solid pellicle of gum 
is formed at the surface of the syrup, the baking will be 
completed, at which time the syrup will mark about 35° B. 
If it be desired to keep the gum in a liquid form, the 
baking must be stopped at 30° while boiling; the syrup 
must then be poured into well-closed vessels, previously 
rubbed with oil of turpentine, and the surface of the gum 
covered with a thin layer of that oil. This method suc- 
ceeded pretty well for preventing the fermentation of the 
liquid gum. 
When it is desired to solidify the gum, the boiling syrup 
is poured into small flat tin vessels, placed upon a hot air 
stove, kept at a temperature of from 72° to 90° F. At the 
end of 24 hours the gum will acquire the consistency of 
jujube paste ; it is then cut up into small oblong pieces with a 
pair of shears, and these pieces are rolled out upon a polished 
table, with a wooden roller, dusted with pulverized artificial 
gum, and afterwards placed upon wooden frames, and left 
for three or four days to dry. The gum would be much 
better dried by letting the syrup run upon a cylinder heated 
to 110° or 120°; but the economy of this process is ques- 
26 
