412 Scientific Intelligence. 
SCIENTIFIC INTELLIGENCE. 
I, CHEMISTRY. 
tter. Gelatin may be considered the type of this class o 
The colloid condition is strongly contrasted with the crystalline, oF Rae 
Graham terms it, the crystalloid, the difference being not oli he 
loids ~~ become gelatinous or wile 
the 
fluid state. The soluble hydrates of silica, alumina and 
sossuertan metallic oxyds, starch, dextrin, gum, albumen, gelatin, case!™, 
&e., are colloids. Graham considers the colloidal _ to be the dynamic 
while ‘et erystalloidal is the statical form of matt 
ery simple method of separating bodies by “diffusion consists in 
phidiig the mixture in a cylindrical glass vessel, five or six inches in 
depth, and filling the vessel with water very carefully so.as not to disturb 
the matter at the bottom. After a few days the upper layers of water 
may be drawn off ‘by means of a pipette and contain the most diffusible 
+ sega im solution. 
f the vessel may ee from eight to tw diva inches, sie ita tps three 
inches. To illustrate the use of this apparatus, a mixed solution of gam 
and sugar may be introduced into the vessel so as to cover the bottom 
bis Graham explains this action s opines that the sugar takes UP ad 
, aeeaoag the colloidal membrane has absorbed, and ip this manne? 
—— by the membrane an consequently ¢8 
hor applies the method of Jalsa to the roe 
in a state of purity, ae even iD * jl 
