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the liquid whose vapour is to be tried ; on a wire-gauze disc is 

 spread the oxide whose powers as a catalyser are to be tested, and 

 this being warmed (more or less) over the lamp, is set down upon 

 the upper rim of the capsule. Sometimes it is necessary to heat a 

 layer of the oxide in the middle of a small combustion-tube, and 

 pass over it the gas, or mixture of gases. 



I tried the following substances with pyroxylic spirit (hydrated 

 oxide of methyl) and alcohol separately. 



1. Co.O appeared to possess the power in some degree, but per- 

 haps the specimen was in too dense agglomeration, which is not 

 essentially reduced by trituration. 



2. Co 2 O 3 maintained the catalytic combustion very well. 



3. Ag.O, reduced to metallic silver, which shows a strong ten- 

 dency on gauze, and acts perfectly in the combustion- tube. 



4. U 2 O 3 , HO became, at red heat, anhydrous mixture of U O 

 and U 3 O 4 , showing strong tendency. A very pure specimen cata- 

 lysed the vapour as it changed from yellow to green, after which it 

 died away. Will not act below 570 (F.). 



5. Sn.O; strong tendency. 



6. Sn.O. 2 ; slight tendency. 



7. W. O 3 apparently produces the effect if placed while glowing, 

 over alcohol, but gradually dies away, as if very slowly cooling. 



8. Pb 3 O 4 changed to Pb . O, and showed a strong tendency, but 

 quickly faded and grew cold. 



9. Cd, O, placed while very warm over pyroxylic spirit, burst into 

 glow and catalysed, but always died off after the lapse of from half a 

 minute to two or three minutes, and then became incapable. 



10. Ca.O (on the gauze), no effect. 



11. Si. O 2 exhibited a tendency. 



12. Stourbridge clay ; no effect. 



13. ALjOg appeared to have no effect in maintaining catalytic 

 combustion on the gauze, but when made red-hot and quenched in 

 absolute alcohol, it changed from pure white to a black substance 

 and oxidized a portion of the alcohol. That this is not owing to 

 carbon in the alcohol is evident, because the same change occurs 

 when it is quenched in strong liquid ammonia. I suspect that it is 

 a new oxide of aluminium. 



14. Ni 2 O 3 , formed by heating carbonate of nickel nearly to red. 



