PROFESSOR GRAHAM ON OSMOTIC FORCE. 
205 
These three chlorides, possessing- about double the diffusibility of sugar and 
sulphate of magnesia, should be replaced by half as much water as the latter 
substances. Some approach to this ratio may be perceived amid much irregularity 
in the observed osmose of the chlorides. 
Proceeding now to the salts in which the osmose appearing to depend upon chemical 
properties preponderates greatly over osmose from diffusion, I may introduce these 
substances under the metals which they contain for the sake of their relations in 
composition. 
Potassium and Sodium. 
Hydrate of Potash. — A highly intense osmose appears to be determined by caustic 
alkali, but it is necessary to apply the smallest proportions of alkali to avoid the 
rapid dissolution of the membrane. In double membrane O'Ol per cent, of hydrate 
of potash, or 1 alkali in 10,000 water, gave an osmose of 81 and 58 ms. By four 
times as much alkali, or 0 025 per cent., an osmose of 49 and 6/ ms. was produced. 
These are the greatest effects. 
On increasing the proportion of hydrate of potash to 0‘5 per cent, the osmose sunk 
to 22 and 26 ms. ; with 1 per cent, of hydrate of potash to 13 ms. The permeability to 
hydrostatic pressure was always very great, being never less than one drop in a minute. 
By the action of the alkali in the last experiment the permeability was increased 
from three to nine drops, and the membrane entirely ruined. 
A similar experiment with hydrate of potash was made in albuminated calico with 
similar osmotic results. In the 0'01 per cent, solution an osmose of 76 and 58 ms. 
was observed; in 0'025 per cent, solution 87 and 126 ms. ; in 0‘5 per cent, solution 
15 and 12 ms., and in 1 per cent, solution — 10 ins., or a small negative osmose. The 
permeability both before and after the last experiment was represented by one drop 
in one minute ; in both the half per cent, experiments the permeability was one drop 
in three minutes; in the preceding 0’025 per cent, solutions one drop in 2^ minutes, 
and at the beginning one drop in ten and five minutes with the 0‘01 per cent, solu- 
tions. The alkali first became sensible to the test-paper in the water-jar, in the 
diffusion of the 0'025 per cent, solutions. During both series of experiments the 
temperature ranged from 58° to 62°. 
Carbonate of Potash . — -The high osmose of this salt has already been often referred 
to in illustration of the influence of alkaline salts. The following experiments may 
be compared with those upon the neutral substances lately discussed, particularly in 
regard to their diffusates. They show also the comparative influence of membrane 
applied single and double to an osmometer. 
