146 REPORT — 1893. 



actinometer. "Whilst the disc in the actinometer was exposed to the solar 

 radiations, one of the thermo-junctions was heated, and when the galvano- 

 meter indicated that no current was flowing the thermometers were read. 

 In one case, in which a deflection of 172 divisions was obtained, the 

 current was balanced by a difference of temperature of the two junctions 

 of 8°-27 C. 



If an instrument of this kind could be made photographically self- 

 recording it would constitute an excellent sunshine-recorder, giving not. 

 only the time of the shining of the sun, but also a measure of its intensity. 

 An ordinary reflecting galvanometer would not be very suitable for this 

 purpose, for variations of the earth's magnetism and the possible movement 

 of magnetic bodies in its neighbourhood would vitiate the results. An 

 instrument on the principle of the D'Arsonval galvanometer would be 

 more appropriate, but a few experiments made with such an instrument 

 have not given satisfactory results. Another source of error must be 

 mentioned, namely, the variation of the resistance of the long conducting 

 wires by changes of temperature. 'No doubt all these difficulties might 

 be overcome in. a properly appointed observatory. 



On the Present State of our Knowledge of Electrolysis and Electro- 

 chemistry. Report by W. N. Shaw and T. C. Fitzpatrick. 



Table of Electro-chemical Properties of Aqueous Solutions, compiled bij 



T. C. Fitzpatrick. 



The comparison of the numerical results of electrolytic observations 

 is rendered difficult from the fact that the data are scattered in various 

 periodicals and expressed by different observers in units that are not com- 

 parable without considerable labour. The following table has been 

 compiled with the object of facilitating the comparison. 



In the table are included all the observations, as far as they are known 

 to the compiler, for the metallic salts and mineral acids ; but amongst the 

 solutions of organic substances ai'e not given all those for which Ostwald 

 has made observations, as it was thought that they would add unneces- 

 sarily to the size of the table. Observations for a number of additional 

 substances will be found in Ostwald's papers in ' Journal fiir Chemie,' 

 vols, xxxi., xxxii., and xxxiii., and in the ' Zeitschrift fiir physikalische 

 Chemie,' vol. i. With this restriction it is hoped that no important 

 observations have been omitted, and that in the reduction of results, 

 expressed in such varied units, the table is sufficiently free from mistakes 

 for it to be of service. The data included refer to the strength and 

 specific gravity of solutions, with the corresponding conductivities, 

 migration constants, and fluidities. The several columns are as follows : — 



I. Percentage composition, i.e. the number of parts by weight of the 

 salt (as represented by the chemical formula) in 100 parts of the solution. 



II. The number of gramme molecules per litre, i.e. the number of 

 grammes of the salt per litre divided by the chemical equivalent in 

 grammes, as given for each salt. 



III. The specific gravities of the solutions : in most cases the specific 

 gravities of the solutions are not given by the observers, and the numbers 



