172 
ON THE DIFFUSION OF LIQUIDS. 
water 69.32, crystallised cane sugar 26.74, starch sugar 
26.94, gum arabic 13.24, albumen 3.03. The low diffusi- 
bility of albumen is very remarkable, and the value of this 
property in retaining the serous fluids within the blood- 
vessels at once suggests itself. It was further observed* 
that common salt, sugar, and urea, added to the albumen 
under diffusion, diffused away from the latter as readily as 
from their aqueous solutions, leaving the albumen behind 
in the phial. Urea itself is as highly diffusible as chloride 
of sodium. 
In comparing the diffusion of salts dissolved in ten times 
their weight of water, it was found that isomorphous com- 
pounds generally had an equal diffusibility, chloride of pot- 
assium corresponding with the chloride of ammonium, ni- 
trate of potash with nitrate of ammonia, 'and sulphate of 
magnesia with sulphate of zinc. The most remarkable 
circumstance is, that these pairs are " equi-diffusive," not 
for chemically equivalent quantities, but for equal weights 
simply. The acids differed greatly in diffusibility, nitric 
acid being nearly four times more diffusive than phospho- 
ric acid; but these substances also fell into groups, nitric 
and hydrochloric acids appearing to be equally diffusive ; so 
also acetic and sulphuric acids. Soluble subsalts and the 
ammoniated salts of the metals present a surprisingly low 
diffusibility. The quantities diffused in similar circum- 
stances of the three salts, sulphate of ammonia, sulphate of 
copper, and the blue ammonia sulphate of copper being 
very nearly as 8, 4, and 1. 
When two saltsare mixed in the solution cell, they diffuse 
out into the water atmosphere separately and independently 
of each other according to their individual diffusibilities. 
This is quite analogous to what happens when mixed gases 
are diffused into air. An important consequence is, that 
in liquid diffusion we have a new method of separation or 
analysis fer many soluble bodies, quite analogous in princi- 
ple to the separation of unequally volatile substances in the 
