Chemistry and Physics. 469 



On adding oxygen, however, up to atmospheric pressure, a further 

 small quantity of the gas was absorbed and the heat simultane- 

 ously developed represented the true heat of occlusion of this 

 quantity of oxygen. The results obtained were in close agree- 

 ment with others obtained indirectly, giving as a mean 11 calories 

 for every gram of oxygen occluded. This value agrees well with 

 that given by Thomsen for the heat of formation of platinous 

 hydroxide. Possibly, therefore, the two phenomena may be iden- 

 tical, the water required being present in platinum black dried in 

 a vacuum. 



In a subsequent investigation, the authors studied the action of 

 palladium black in occluding gases. Prepared in the same way 

 as platinum black, it contains 1*65 per cent or 138 times its vol- 

 ume of oxygen. But this oxygen, unlike that in platinum black, 

 cannot be removed by heating to dull redness in a vacuum, but 

 must be heated in a current of hydrogen. When heated in 

 oxygen the palladium black absorbs it, up to a red heat, yielding 

 a brownish black substance, which does not lose its oxygen on 

 heating to redness in a vacuum. Nearly 1000 volumes are 

 absorbed, an amount about three-fourths of that required to form 

 the oxide PdO. Over 1000 volumes of hydrogen are absorbed by 

 palladium black, though only 873 volumes are occluded, the rest 

 having formed water with the oxygen present. About 92 per 

 cent is removed by the air pump at the ordinary temperature, the 

 rest at 444°. The palladium sponge from this experiment occluded 

 852 volumes of hydrogen, of which 98 per cent was extracted in a 

 vacuum at ordinary temperatures. The heat of occlusion for 

 hydrogen was found to be 46*4 calories for each gram of the gas ; 

 or 43 '1 if the work of the atmosphere be allowed for. The heat 

 developed per gram of oxygen occluded, determined indirectly, 

 was found to be 1T2 calories, a value intermediate between that 

 found by Thomsen for the heat of formation of palladious and 

 palladic hydroxides; favoring the idea that this occlusion of oxy- 

 gen is a true oxidation. The atomic ratio of palladium to 

 hydrogen in the fully charged metal varies between 1*37 and 1*47 ; 

 agreeing closely with the formula Pd 3 H (J as suggested by Dewar. 

 —Proc. Roy. Soc, lxii, 50-52, 290-293 ; J. Chem. Soc, lxxiv, 

 ii, 599, 600, December, 1898. G. f. b. 



3. On certain Derivatives of Acetylene. — It has been observed 

 by Erdman and Kothner that when acetylene is passed over 

 finely divided copper heated to 400°-500° it is decomposed into 

 hydrogen and carbon, the latter appearing in the graphitic condi- 

 tion. At temperatures below 250°, however, the copper unites 

 with the gas, forming a yellowish-brown compound which is not 

 explosive. This new substance may be more readily prepared by 

 heating finely divided cuprous oxide in a current of acetylene at 

 250°. It is very bulky, and has the composition C 44 H 64 Cu 3 . 

 When heated with zinc dust in excess it yields 20 per cent of an 

 oil having an odor like Caucasian naphtha and boiling between 

 190° and 250°. Well-defined acetylides of the alkali metals are 



