738 Proceedings of the Royal Society of Edinburgh. [Sess. 
amount of gas, appreciable in atomic weight work, might not be absorbed 
by platinum sponge cooled at atmosjDheric pressure. A great many 
experimenters have investigated this phenomenon. The work of Graham,* 
Smith, -j* Gladstone and Tribe, J Berthelot, § Traube, || Berliner, IT Neumann 
and Streintz,** Wilmf-j* and Mond, Ramsay and Shields JJ should be cited. 
The latter authors, Mond, Ramsay and Shields, concluded from a very 
careful piece of work, that platinum black upon being heated to a red heat 
in a vacuum gave up all of the occluded gases. In order to ascertain 
whether it would be necessary to heat and weigh the platinum sponge in 
a vacuum, the following experiments were carried out. 
A few grams of platinum sponge were placed in a platinum boat and 
carefully weighed. The boat and sponge were then placed in a hard glass 
tube, and this connected by means of a stopper and a mercury seal with a 
Topler pump. The tube was then evacuated to a few tenths of a mm. 
pressure, and the tube containing the boat and sponge heated until the glass 
began to soften. The pump was again evacuated while the tube was being 
heated, and all the gas which could be driven off was pumped away. The 
boat and sponge were now allowed to cool, and the tube sealed off at a 
point which had been drawn out. After desiccating a long while, the tube 
containing the boat and sponge was weighed, using as tare a tube of the 
same kind of glass, and of the same diameter, as the tube which had been 
heated, and sealed off under the same pressure. 
The first tube was now broken under conditions which ensured no loss 
of glass, at a scratch made on it before heating ; the platinum boat and 
sponge were withdrawn and the glass weighed. As the tube used as tare 
had been broken for this weighing, only a small buoyancy correction has 
to be applied if the two tubes have been carefully chosen. We have now 
all the data necessary for finding the difference in weight of the platinum 
when heated, cooled and weighed in air, and when the same operations are 
carried out in a vacuum. Several such experiments were carried out, and 
they all gave negative results, showing that the difference in weight of 
the platinum under these different conditions was not larger than the 
experimental error of the determination. 
* Proc. Roy. Soc., xvi. 422 (1868). 
t Ghem. News, xxxi. 55 (1875). 
j. Jour. Ghem. Soc., xxxv. 172 (1879). 
§ G . R., xciv. 1377 (1882). 
|| Ber. Deutscli. Ghem. Gesell., xv. 2854 (1882). 
1 Ann. der. Phys. (Pogg.), [2] xxxiii. 289 (1888). 
** Monatsh. Ghem., xii. 642 (1891). 
tt Jour. Russ. Ghem. Soc., xxiv. I. 241 (1892). 
f l Proc. Roy. Soc., lviii. 242 (1895). 
