COLLOIDS AT WORK. 
Colloids at Work.” 
Aids to Industry. 
Graham discovered that if parchment or parchment paper is stretched over 
a frame to make a diaphragm, that such a diaphragm or membrane will separate 
substances into two great classes: Those which can pass through in solution 
and those which cannot or only do so with great difficulty. The substances 
which can pass are usually capable of being crystallized, while the others are 
jelly-like and their solutions have properties which differ markedly from solutions 
of well-known crystals. A favorite experiment is to place a solution of salt 
and of glue in a membrane on the other side of which water flows slowly. The 
salt passes through into the water, and soon the glue only is to be found in the 
membrane-covered cell. 
This principle has been applied commercially in several industries, and is 
rariously styled dialysis, diffusion, osmosis, &e. Some erystalline substances 
diffuse more rapidly than others, so that certain separations can be made between 
crystalloids as they were originally called. Sometimes the vegetable cell itself 
becomes the membrane through which sugar, for example, is extracted by 
treating the sliced hect, in this instance, with suecessive changes of water. The 
temperature is made such that the albumins are first coagulated in the cell 
walls, thus facilitating the passage of the sugar solution, and then eight ‘or 
more changes of water are brought into contact with the pencil-size V-shaped 
slices upon the counter current principle. This allows fresh water to take the 
last of the sugar (all but about 0.5 per cent., for it is not economical to carry 
the extraction below that figure) from the nearly exhausted pulp, and the juice 
of highest sugar content to be drawn from the first cell for purification. 
In the beet sugar industry, we also find an example of osmosis using a 
membrane. A point is reached in crystallizing out the sugar when eyen impure 
crystals cannot be won from the residual molasses. This molasses contains above 
50 per cent. of sucrose, and is unlike molasses from cane in being unsuited for 
human use. The sugar is recovered by precipitation with strontium of lime, or 
by osmosis. In the latter method, the diluted molasses passes slowly along one 
side of a series of membranes, and water flows in the opposite direction on the 
other side. A large percentage of the sugar passes through. : 
Within comparatively recent years, colloids haye been studied more intently, 
and much work has been done in an effort to learn more of what actually takes 
place in reactions involving them. ‘Their aqueous solutions, when pure, have the 
same boiling and freezing points as the solvents themselves, so the conclusion 
is that they are not true solutions but excessively fine particles in suspension. 
These particles pass through the finest filter papers, and some are too small 
to be seen under the microscope. The ultra-microscope enables some studies to 
be carried on through the observation of the shadows cast by the particles and 
light reflected by them. Colloidal gold is responsible for the beautiful ruby 
glass, and colloidal copper was used for red signal glass until chemistry pointed 
the way for the employment of selenium to produce that colour. 
There are many who grow impatient awaiting some practical results from 
academie¢ research, which seems at times to move with the speed of a glacier, 
and yet progress is not made without such research. How often curative medicine 
has been compelled to wait until a way of communicating the disease under 
investigation to lower animals for study could be devised. We know now how 
to prepare colloidal suspensions, and that will lead to many commercial applica- 
tions. At least two may be mentioned as accomplished, and one of these has 
been developed as a result of the war. 
The importance of a concentrated, easily handled, efficient fuel for war and 
merchant vessels is obvious, and in times of emergency, when speed and space 
count for: most, this importance is greater than ever. <A colloidal chemist con- 
ceived the idea of fortifying fuel oil with colloidal coal so fine and in such a 
physical condition that it would be permanently in suspension, go where the oil 
would, and pass through the small orifices of valves and burners without clogging 
them. Experiments showed the idea to be sound, and its further development 
will be an efficiency and conservation measure, : 
* Extracted from Scientific American. 
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