2S8 ON THE MANUFACTURE OF ARTIFICIAL GUM. 
be more rapid ; but a larger quantity of glucose would be 
formed, and the gum would be more coloured. With regard 
to the utility of the mucilage of linseed, it imparts tenacity 
to the gum. Instead of this substance I attempted to use 
lichen; but it did not answer, although the products were 
much whiter, by reason of the mucilage depositing itself 
upon the sides of the boiler, and preventing the liquid from 
boiling. It is, besides, not so strong as the linseed mucilage. 
The mixture must be kept at a temperature of about 122° 
or 140° until all the starch is again dissolved ; the tempera- 
ture should then be suddenly raised, taking care however 
not to exceed 167°, but keeping as near that temperature 
as possible, in order to cause the diastase to act as power- 
fully as possible. It will then be necessary to stir the mix- 
ture well until the decomposition is almost complete ; this 
may be ascertained by the deep blue tint the mixture 
assumes, and by the action of the solution of iodine, which 
in that case will colour the dextrine of a violet, approaching 
to red, without any mixture of blue. 
It is unnecessary to say, that, during the decomposition, 
the liquid must be kept constantly in motion. The opera- 
tion lasts about an hour and a quarter ; that is to say, a 
quarter of an hour for the formation of the paste, one for its 
dissolution, and the other three-quarters for rendering it 
soluble. 
I much prefer this method of forming the paste to adding 
the malt, as the reagent spreads much more uniformly 
throughout the mass, and does not at once fail to the bottom 
of the vessel in which the operation is performed. 
The liquor must now be removed from the decomposing 
vats, and left in pans to settle for from 6 to IS hours, 
according to the external temperature. During this time a 
slight fermentation will be perceptible, but it must be 
checked by adding alum in the proportion of 10 grms. for 
every 25 gallons of liquid. It is essential to allow this time 
for the mixture to settle, as it prevents two serious evils: 
viz, the colouring of the gum while baking, and a singular 
