PROFESSOR GRAHAM ON OSMOTIC FORCE. 
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in l per cent, solutions of the substances, salicin 5 ms., tannin 3 ms., urea 4 ms., 
gelatin 9 ms., amygdalin 6 ms., lactine 7 ms., glucose 7 ms., gum-arabic 18 ms., and 
hydrochlorate of morphine 4 ms. 
The relations to osmose of alcohol and sugar were more fully examined. With 
these and other chemically inactive substances, the osmose, although small for 
1 per cent., increases progressively with larger proportions of the substance, and also 
bears a close relation to the proportion of substance diffused outwards, circumstances 
which give a mechanical character to the osmose. It is with such substances that the 
influence of diffusibility upon osmose is most likely to betray itself. They have a 
peculiar interest in the study of the phenomenon, as they present a certain small 
but remarkably uniform amount of osmose without the known intervention of any 
strong chemical affinities. 
Alcohol . — In describing an experiment I shall endeavour to put forward all the 
circumstances which can be supposed to influence in any way the result. 
In the table which follows, Column I. contains the proportion of absolute alcohol, 
by weight, which is dissolved in the water of the osmometer. 
A 10 per cent, solution is prepared by weighing 10 grammes of the substance, 
and then adding water to it so as to make up the liquid to the volume of 100 grammes 
of water. It is necessary to make up in this way solutions used in experiments of 
diffusion and osmose, in order to preserve a true relation in solutions containing the 
different proportions of substance, for it is a fixed volume (not weight) of these solu- 
tions which must be used in the osmometer. We come thus to have with a 20 per 
cent, solution of alcohol exactly twice as much alcohol in the osmometer as with a 
10 per cent, solution of alcohol, and so of other proportions. 
The membrane of the osmometer is always to be considered as fresh, or as used 
for the first time in the first experiment narrated, and the observations to be made 
successively as they stand in the table. The length of maceration in cold water to 
which the membrane has been exposed previous to the osmotic experiment, as before 
described, is given in Column V. By the most frequent time of one day is to be 
understood the space of eighteen hours, which intervened between experiments on 
successive days. 
The hydrostatic resistance of the membrane given in Column VI. is the length of 
time, in minutes, observed to elapse between the fall of two drops from the bulb of 
the osmometer filled with distilled water, and hung up in air as already described. 
The temperature of the water in the glass cylinder during the experiment is noted 
in Column VII.; the rise of fluid in the tube of the osmometer or osmose, in milli- 
meter divisions of the tube, appears in Column II., and the absolute amount of the 
same osmose is expressed in Column III. in grammes, or more strictly in gramme 
measures of water. Lastly, the weight of diffusate found in the water of the glass 
cylinder appears in Column IV. These last two data, the osmose and diffusate, 
both in grammes, afford the means of comparing the weight of substance which has 
2 c 
MDCCCLIV. 
