222 ANNUAL OF SCIENTIFIC DISCOVERY. 



ing action latent heat becomes sensible heat, and the contiguous parti- 

 cles must therefore be raised in temperature while the freezing water 

 is between them. It follows from this that, by virtue of the solidifying 

 power at the points of contact, the same mass may be freezing and thaw- 

 ing at the same moment, and even that the freezing process on the in- 

 side may be a thawing one on the outside. London Athcnczum, June. 



ON THE DIFFUSION OF LIQUIDS. 



A SALT or other soluble substance, once liquefied and in a state of 

 solution, is. evidently spread or diffused uniformly through the mass of 

 the solvent by a spontaneous process. It has often been asked whether 

 this process is of the nature of the diffusion of gases ; but no satisfac- 

 tory answer to the question appears to have been obtained, owing to 

 the subject having been studied chiefly in the operations of endosmo- 

 sis, where the action of diffusion is complicated and obscured by the 

 imbibing power of the membrane, which appears to be peculiar for 

 each soluble substance, but not to be necessarily connected with the 

 diffusion of the substance in water. In order to avoid this source of 

 fallacy, Prof. Graham has studied the phenomena with an apparatus 

 constructed as follows. It consisted of an open phial, to contain the 

 solution of the salt to be diffused, which he calls the " solution cell " ; 

 which was entirely immersed in a large jar of pure water, so that the 

 solution in the ; phial communicated freely with the latter, the two 

 together forming a " diffusion cell." The diffusion was stopped gen- 

 erally 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 " dif- 

 fusion 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, 1.29, 3.01, and 

 4.00; and that, in repetition of the experiments, the results did not 

 vary more than one fortieth part. The proportion of salt which diffused 

 out in such experiments amounted to about one eighth of the whole. 

 Secondly, that the proportion of salt diffused increased with the tem- 

 perature ; an elevation of 80 F. doubling the quantity of chloride of 

 sodium diffused in the same time. 



The diffusibility of a variety of substances was next compared, a 

 solution of 20 parts ot the substance in 100 of water being always 

 used. Some of the results were as follows, the quantities diffused 

 being expressed in grains: Chloride of sodium, 58.68 ; sulphate of 

 magnesia, 27.42 ; crystallized cane-sugar, 26.74 ; starch-sugar, 26.94 ; 

 gum Arabic, 13.24 ; albumen, 3.08. The low diffusibility of albumen 

 is very remarkable, and the value of this property in retaining the 

 serous fluids within the blood-vessels at once suggests itself. It was 

 further observed, that common salt, sugar, and urea, added to the albu- 



