PROFESSOR GRAHAM ON THE DIFFUSION OF LIQUIDS. 
831 
perties, which was not the case with the equidifFusive group containing the hydrogen 
acids of the same salt-radicals (p. 807). 
35. Chloride of Ammonium. 
Time of diffusion 5 ‘716 days. The salt diffused was estimated by means of nitrate 
of silver. 
Solution 0-988 per cent. ; density r0036. Diffused at 53°^ in eight cells, 6-09, 6 07, 
5-67, 5-87 ; mean 5-92 grs., and 5-99 for one per cent, in two cells. This is somewhat 
more than 5-68, one-half of the diffusate of the 2 per cent, solution of iodide of 
potassium, at nearly the same temperature. The diffusion, however, of the small 
proportions of salts of ammonium, such as the 1 per cent, solution, is apt to be given 
in excess, from their low density. 
36. Dichloride of Copper. 
Time of diffusion seven days, or that of chloride of sodium. The salt diffused was 
obtained by evaporation to dryness, in an air-bath, after treating the liquid with an 
excess of chlorine, in the form of chloride, from which the dichloride was calculated. 
It was an object of interest to discover whether the dichloride of copper (Cu 2 Cl), 
which should be isomorphous with the chloride of sodium, may separate from the 
protochloride of copper and other magnesian salts, and assume the high diffusibility 
of the salts of alkaline metals. But the salt in question is entirely insoluble in water. 
A solution, however, vms obtained by dissolving an equivalent quantity of the red 
suboxide of copper recently precipitated, in hydrochloric acid, of density r033, so as 
to give one grain of dichloride in every hundred water-grain measures of the solution. 
This acid solution did not precipitate by dilution with water. The salt was diffused 
into pure water at a mean temperature of 53°-2. 
1. Dichloride of copper diffused, 6-66, 6'57, 7‘61 and 6'48 grs. ; mean 6-68 grs. in 
two cells. Chloride of sodium at 53°-4, nearly the same temperature, gave 5-90 grs. 
in the same time. Reducing the result to the temperature of 51° by an approxima- 
tive correction, we should have 6-48 grs. of dichloride of copper for that temperature, 
at which chloride of calcium gave 6-51 grs. in 1T43 days, and protochloride of copper 
(Cu Cl) 6*06 grs. at nearly the same temperature, also in 1T43 days. 
So far as we can judge from an experiment at a single temperature, it would ap- 
pear that the diffusion of dichloride of copper is more rapid than that of the chloride 
(Cu Cl), in a proportion which supposes the former compound to possess half the 
“solution-density” of the latter, the times of equal diffusion 7 and 11*43 days, being 
when squared as 1 to 2. 
With the view of discovering whether the large proportion of hydrochloric acid, 
amounting to 7 per cent., present in the preceding solution of dichloride of copper, 
modified the diffusion of the salt, a portion of the same acid solution was treated with 
chlorine gas, to convert the copper salt into chloride, and diffused into water, after 
