ON THE DIFFUSION OF LIQUIDS. 
171 
water, so that the solution in the phial communicated freely 
with the latter. Phials cast in a mould of the capacity of 
four ounces of water, or more nearly 2,000 grains, were gen- 
erally employed, which were ground down to a uniform 
height of 3.S inches. The neck was 0.5 inch in depth, and 
the aperture or mouth of the phial 1.25 inch in diam- 
eter. The phial was filled up with the solution to be diffused 
till it reached the point of a pin, dipping exactly 0.5 inch 
into the mouth of the bottle. This being the solutiori cell 
or bottle, and the external jar the " water jar," the pair 
together forma "diffusion cell." The diffusion was stopped 
generally after seven or eight days, by closing the mouth of 
the phial with a plate of glass, and then raising it out of the 
water jar. The quantity of salt which had found its way 
into the water jar — the diffusion product as it was called — 
was then determined by evaporating to dryness. 
The characters of liquid diffusion were first examined in 
detail with reference to common salt. 
It was found, first, that with solutions containing 1, 2, 3, 
and 4 per cent, of salt, the quantities which diffused out of 
the phials into the water of the jars, and were obtained by 
evaporating the latter, in a constant period of eight days, 
were as nearly in proportion to these numbers, as 1, 1.99, 
3.01, and 4.00 ; and that in repetitions of the experiments, 
the results did not vary more than l-40th part. The pro- 
portion of salt which diffused out in such experiments 
amounted to about 1-Sth of the whole. 
Secondly, that the proportion of the salt diffused increases 
with the temperature ; an elevation of 80° Fahr. doubling 
the quantity of chloride of sodium diffused in the same 
time. 
The diffusibility of a variety of substances was next com- 
pared, a solution of 20 parts of the substance in 100 water 
being always used. Some of the results were as follows, 
the quantities diffused being expressed in grains : — Chloride 
of sodium 58. 6S, sulphate of magnesia 27.42, sulphate of 
