6 
PROFESSOR GRAHAM ON THE DIFFUSION OF LIQUIDS. 
I. CHARACTERS OF LIQUID DIFFUSION. 
1. Diffusion of Chloride of Sodium. 
The characters of liquid diffusion were first examined in detail in the case of this 
salt. 
(1.) Do different proportions of chloride of sodium in solution give corresponding 
amounts of diffusion ? 
Solutions were prepared of chloride of sodium in the proportion of 100 water with 
1, 2, 3 and 4 parts of the salt. 
The diffusion of all the solutions was continued for the same time, eight days, at 
the mean temperature of 52°'5 Fahr. 
Proportion of salt to 100 water. 
Diffusion product. 
In grains. 
Ratio. 
1 
2-78 
1- 
2 
5-54 
1*99 
3 
8*37 
3-01 
4 
IMl 
4-00 
The quantities diffused appear therefore to be closely in proportion (for this salt) 
to the quantity of salt in the diffusing solution. The density of the solutions con- 
taining 1, 2, 3 and 4 parts of chloride of sodium, was at 60°, T0067, T0142, T0213, 
T0285. The increase of density corresponds very nearly with the proportion of 
chloride of sodium in solution. A close approach to this direct relation is indeed 
observable in most salts, when dissolved in proportions not exceeding 4 or 5 per 
cent. 
The relation which appears in these results is also favourable to the accuracy of 
the method of experimenting pursued. The variation from the speculative result 
does not in any observation exceed 1 per cent. 
(2.) Is the quantity of salt diffused affected by temperature ? 
The diffusion of similar solutions of chloride of sodium was repeated at two new 
temperatures, 39°'6 and 67°, the one being above and the other below the preceding 
temperature. It was necessary to use artificial means to obtain the low temperature 
owing to the period of the season. A close box of double walls, namely, the ice-safe 
of the Wenham Ice Company, was employed, masses of ice being laid on the floor of 
the box, and the water-jars supported on a shelf above. The water and solution were 
first cooled separately for twenty-four hours in the ice-box, before the diffusion was 
commenced. It was found that the temperature could be maintained within a range 
of 2° or 3° for eight days. It was doubtful however whether the temperature was 
constantly the same to a degree or two in all the jars ; and the results obtained at 
an artificial temperature were always less concordant and sensibly inferior in preci- 
sion to observations made at the atmospheric temperature. 
