ORs wid a Physics. a 107 
It, su ur 
men under diffusion, diffused away fa the latter as readil 
, dees solutions. Urea itself is as highly diffusible as ‘chignid . 
<> -.O * 
ee. In comparing the diffusion of salts dissolved in 10 times s their weight ~ 
i ® of water, it was found tha at isomorphous compounds generally bad an 
“is. equal diffusibility, chlorid of potassium corresponding with chlorid of 
<= amm monium, nitrate of potash with nitrate of ammonia, and sulphate of 
2 . ae 
cies 
rochloric acids appearing to be equally diffusive ; so cetic and 
sulphuric acids, Soluble sub-salts mmoni of the 
metals present a surprisingly low diffusibility ; the ib scot diffused i 
-Sitilar circumstances of the three salts, sulphate of ammonia, sulphate 
of copper, and the blue ammonio- sulphate of So iper being very nearly 
as 
o salts are mixed in the solution- ite they diffuse out into 
the water sew osphere separately and indepe ently of each other, ac- 
cording to shai individual diffusibilities. This i is quite analogous to what 
appens when mixed gases are diffused into air. An important con- 
Sequence is, that in liquid diffusion we have a new method of separation 
or analysis for many soluble bodies, quite analogous in principle to the 
_ Separation of unequally volatile substances in the process of distillation. 
“Aa it was shown that chlorids diffuse out coven sulphates and — 
Salts diffusing up into the sheet of fresh water, with which the lake is 
Periodically covered, with unequal velocity. 
t was further shown that chemical decompositions may be produced 
by — patie the constituents of a double salt of so much sta- 
bility as common alum being separated, and the hella of potash 
difasing i in be largest proportion. In fact the diffusive force is one of 
great energy, and quite as capable of breaking up compounds as the 
unequal volatility of their constituents. Many empirical operations in the 
chemical . = 
ter; the salts appearing mutually diffusible, as gases are known to be. 
Lastly, the diffusibilities of the salts into water, like those of the 
geses into air, appear to be connected by simple numerical relations. 
