1879.] Mr. G. Matthey. On the Platinum Series. 



4153 



other. They indicate the temperatures of the layers in which they 

 are placed. 



Now, if we know the difference of temperatures of two sides of a 

 stratum of a liquid during any time, and the quantity of heat con- 

 ducted across the stratum during that interval of time, we can 

 calculate the thermal conductivity of the liquid by means of a well- 

 known formula. 



The result arrived at by the experiments described, is- that the 

 thermal conductivity of water may be taken at from "0022. to '00245 

 in square centimetres per second. 



Some experiments have been made on the thermal conductivity of 

 solution of sulphate of zinc, a solution which happened to be con- 

 venient for preliminary trials. The specific heat of solution of 

 sulphate of zinc at different densities, which it is necessary to know 

 for comparison as to thermal conductivity of that liquid with water, 

 has been determined. 



Experiments are now being- carried on on this subject with the 

 assistance of a grant from the Government Fund of 4,000L 



II. "The Preparation in a State- of Purity of the Group of 

 Metals known as the Platinum Series, and Notes upon the 

 Manufacture of Iridio-Platinum." By George Matthey. 

 Communicated by F. A. Abel, C.B., F.R.S. Received 

 March 19, 1879. 



In this paper it is not nry intention, nor should I be able, to refer 

 generally to the results of work in the various branches- of platinum 

 metallurgy carried out by my firm, who, as is well known, have been 

 associated with the development of this special field of industry from 

 its earliest infancy ; but I shall confine myself simply to that section 

 of it upon which my personal attention has of late years been speci- 

 fically concentrated in order to meet and comply with the requisition 

 of the Bureau Internationale des Poids et Mesures, the Section 

 Francaises de la Commission Internationale du. Metre,, and of l'Asso- 

 ciation Geodesique Internationale (all of them important scientific 

 committees, formed with the object of arriving at an accurate and 

 definite solution of the long agitated question of standard weights 

 and measures), and also' at the demand of the French Minister of War, 

 for an alloy the best adapted for the manufacture of the international 

 metre and kilogram standard,, and the geodesique rule; and in my endea- 

 vour to solve this difficult problem I have had the great advantage of 

 being able to consult those distinguished men, M.M. Henri Sainte 

 Claire Deville and Henri Debray, of Paris, and have also had the 



2 m2 



