242 Messrs. L. Mond, W. Ramsay, and J. Shields. [June 20, 



These results are taken from a longer paper on panmixia and 

 regression, which ill-health has prevented my completing up to the 

 present date. 



VIII. " On the Occlusion of Oxygen and Hydrogen by Platinum 

 Black. (Part I.)" By LUDWIG MOND, F.R.S., WILLIAM 

 RAMSAY, Ph.D., F.R.S., and JOHN SHIELDS, D.Sc., Ph.D. 

 Received June 13, 1895. 



(Abstract.) 



The authors describe some preliminary experiments on the occlusion 

 of oxygen and hydrogen by platinum sponge and foil, which in general 

 confirm the results obtained by Graham. At most only a few volumes 

 of these gases are occluded by the more coherent forms of platinum. 



After giving details of what they consider the best method of pre- 

 paration of platinum black, they next describe some experiments 

 which had for their object the determination of the total quantity of 

 water retained by platinum black, dried at 100 C., and the amount 

 of water which can be removed from platinum black at various tem- 

 peratures in vacuo. As the result of these experiments they find that 

 platinum black dried at 100 retains in general 0'5 per cent, of water, 

 and this can only be removed in vacuo at a temperature (about 400) 

 at which the black no longer exists as such, but is converted at least 

 partially into sponge. At any given temperature the water retained 

 by platinum black seems to be constant. The density of platinum 

 black dried at 100 C. is 19'4, or allowing for the water retained by it 

 at this temperature, -21*5. 



The amount of oxygen given off by platinum black at various tem- 

 peratures was determined. Altogether it contains about 100 volumes 

 of oxygen ; the oxygen begins to come off in quantity at about 300 C. 

 in vacuo, and the bulk of it can be extracted at 400 C., but a red heat is 

 necessary for its complete removal. Small quantities of carbon dioxide 

 were also extracted, chiefly between 100 200 C. 



In determining the quantity of hydrogen occluded by platinum black 

 the authors have carefully distinguished between the hydrogen which 

 goes to form water with the oxygen always contained in platinum 

 black, and that which is really absorbed by the platinum per se. 

 Altogether about 310 volumes of hydrogen are absorbed per unit 

 volume of platinum black, but of this 200 volumes are converted into 

 water, or only 110 volumes are really occluded by the platinum. Part 

 of it can be again removed at the ordinary temperature in vacuo ; by 

 far the larger portion can be extracted at about 250 300 C., but a 

 red heat is necessary for its complete removal. The amount of hydro- 



