222 
MESSES. W. DE LA EUE AND H. W. MtJLLER ON THE 
The two tubes about to be described present some very remarkable phenomena, 
which show that the terminals in some cases are able to absorb the gases of the 
vacuum tubes and to give them off again under the influence of the current. 
Tube 48, length 7 inches , between the terminals 2f inches, diameter 1-| inch. 
228. — The residual gas is hydrogen, the negative terminal a spiral, the positive a 
straight wire, both of palladium 0'05 inch diameter; with 1200 cells, 
C. 0'01331 W, with 2400 cells, C. 0'0237l W ; in the latter case the deflection 
of the galvanometer was reproduced by 40,000 ohms inserted in the circuit 
in lieu of the tube. 
Both wires before the experiment were bright and metallic ; there were 
produced six strata at the positive and a glow around the negative, a copious 
mirror-like translucent deposit forming on the tube about the negative, which, 
examined by the microscope with a power of 260-570 linear, appeared to 
consist of cubes or four-sided prisms T 2 oFo inch across. If the current was 
continued for about a minute a central zone was cleared by the heat and 
the deposit carried further along the tube. Gradually there was formed a 
similar deposit, but not so dense, on the tube round the positive terminal. 
The curious part of the phenomenon is that the negative and positive 
terminals, having become mat and black as if covered with a deposit of 
spongy palladium, resume their metallic appearance on laying the tube 
aside for a week or two ; in the mean time the deposit is entirely 
re-absorbed by the terminals, which become white like frosted silver, and 
the glass is left quite clear. This experiment has been repeated very many 
times with the same result. Is the deposit a definite compound of palladium 
and hydrogen ? * 
Tube 49, length 9 inches, between the terminals 3| inches, diameter If inch. 
229. — The residual gas hydrogen, the negative terminal a spiral of palladium, the 
positive an aluminium wire; 2400 cells, C. 0 '01982 W; the resistance 
reproduced by 70,000 ohms. Similar phenomena were produced, except that 
around the positive terminal, the aluminium wire, there was no deposit. 
We have made several experiments with tubes containing other gases besides those 
already mentioned, for example : — hydrochloric, HC1, hydrobromic, HBr, and hydro- 
fluosilic, 4HF,SiF 4 , acids; carbonic oxide, CO, olefiant gas, C 2 H 4 ; phosphoretted 
hydrogen, PH 3 ; arsenetted hydrogen, AsH 3 ; dioxide of nitrogen, N 3 0 2 . But we 
have nothing special to mention at present with respect to them, and they all require 
a more extended study. 
* Graham, 1 Chemical and Physical Researches,’ collected by Angus Smith, 1876, pp. 281-299. 
Troost and Hautefeuille, ‘ Comptes Rendus,’ lxxviii. pp. 686-690, describe a compound Pd 2 H. 
