Intelligence and Miscellaneous Articles. 297 



The motion of diffusion has two properties in common with 

 wave-motion, which follow from the linear form of the differential 

 equations determining the laws of these motions. The first is the 

 superposition of the diffusion-currents which start from different 

 parts of the liquid ; the second is the complete reflection which 

 the diffusion-currents undergo at the boundaries of the liquid. 

 Both properties can with great advantage be made use of in the 

 calculation of Tables. The memoir contains also a formula, based 

 on them, which permits the diffusion-coefficient to be calculated in 

 a very simple way from a combination of the salt-contents of the 

 individual layers. 



As regards the amount of these coefficients Jc, inter alia there 

 were found : — 



For Caramel (temp. 10°) &=0-047 



Albumen (13°) &=0-063 



Cane-sugar (9°) &=0'312 



Chloride of sodium (5°) . . &=0-765 

 (9°) .. &= 0-910 

 Hydrochloric acid (5°) .... &=l-742 

 and these numbers have for base the centimetre as unit of length, 

 and the day as unit of time. 



In relation to the diffusion of quantities of salt, older experi- 

 ments of Graham, and Marignac's comprehensive experiments 

 especially, have taught us that the parts of the mixture essentially 

 effect one another, so that the more diffusible of the two salts in 

 the mixture diffuses still more quickly, and the other still more 

 slowly, than when it alone is present. Also, from the experiments 

 here discussed it follows, at the same time, that the distribution of 

 each of the two salts, especially of the more quickly diffusing one, 

 sensibly deviates from the laws of simple diffusion. So much more 

 remarkable is it that the distribution of the mixture as a whole, as 

 shown by the series under III., so closely conforms to those laws. 

 There are two experiments of this kind specially important. 

 The first refers to a mixture of chloride of potassium and sulphate 

 of soda, the second to a mixture of chloride of sodium and sulphate 

 of potass. Both proceed in almost the same way ; and although 

 Graham did not complete the analyses, it may yet be concluded 

 from his statements that the upper layers contained chloride of 

 potassium in the second experiment also. 



Such cases of decomposition by diffusion, as Graham calls them, 

 were already known from his older experiments. It is more correct 

 to assume that the decompositions take place in the mixture before 

 the diffusion, and that the latter only acts the part of a sieve which 

 lets through more readily the one product than the other. — Kaiser - 

 liche Akademie der Wissenschaften in Wien, math.-naturw . Classe, 

 1879, No. 3, pp. 24-27. 



ON THE SPECTRUM OF OXYGEN, AND ON THE ELECTRICAL LUMI- 

 NOUS PHENOMENA OF RAREFIED GASES IN TUBES WITH LIQUID 

 ELECTRODES. BY M. PAALZOW. 

 As a rule, in the examination of the electrical luminous pheno- 



Phil Mag. 8. 5. Vol. 7. No. 43. April 1879. 2 A 



