lOG DENSITIES OF OXYGEN AND HYDROGEN 



after exliaustion .and befoie the measurement of the vai-uum, so as to make sure of 

 an equilibriiiiii of jiressure. Once sucli a leak was detected ; when the apparatus 

 was dismounted, and the globes weighed again. A leakage during the second 

 weighing ought to be detected by the slow change of weight which it produces. 

 It was not detected during an \ of the experiments of the present series. It may 

 be said that the stopcocks of five of my globes were of large size so as to make the 

 distance which air must travel around the key, fiom the entrance to the exit, as 

 nuich as four centimetres. These were often found to be tight for some days when 

 freshly lul)ricated and turned but a few times. 



It was to avoid both these eri'oj-s that, in the last thi'ee experiments, the globes 

 holding oxygen wei'e closed in the same way as the tube containing the palladium 



Two sources of error in the determination of the weight of water pioduced 

 were known to exist. The platinum wires foi- the passage of the spark might be- 

 come loosened by the heat, so as to admit some water or aii-. On the other hand, 

 the exhaustion by means of a Toepler [)uiiip. unless regulated by opening the stop- 

 cock but partly, may sometimes diaw the gas through the drying tubes fastei' than 

 it can be dried. Piobaldy this happened, to a slight extent, in some of the experi- 

 ments, but the amount was not very large. The manipulation which might have 

 easily and completely prevented this was not thought of till the second ( untinislied ) 

 series of experiments was begun. 



13. — SYNTHESIS OF WATER. COMPLETENESS OF DRYING OF GASES WUTI PlIOSPHORDS 



PENTOXIDE. 



In a i)aper describing some of the earliest of my experiments lelating to oxygen 

 and hydrogen, it is shown that the amount of moisture left by pliosplioius pentoxide 

 in even a thousand litres of a gas is negligible. My experiments proveil that a cur- 

 rent at the rate of three litres an hour was made absolutely dry by a rightly tilled 

 tul)e whose capacity was twenty-live cubic centimetres; it was therefore thoiiLrht 

 safe to pass a curient of twelve litres an hour through a tube containing one hun- 

 (iifd cubic centimetres. 



14. SYNTHESIS OK WATER. IS MVDROfiEN GIVEN ol I l!V I' \I,I. ADIIM FREE 



I'KOM WATER? 



A source of error would exist if, as has been thought, water should accompany 

 the hydrogen delivered from palladium. This would imply that oxygen in some 

 way found access to the palladium, and that tlie water produced was not removed 

 with any nitrogen which might have accompanied the hydrogen. Keiser considered 

 his experiments as proving that water is given off from palladium together with 



