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ness, failed ; prepared from the common nitrate, it acted for a short 

 time ; reduced as an intensely black velvety substance from the purest 

 nitrate, then warmed but not made red-hot, it glowed and catalysed 

 with alcohol or ether. With pyroxylic spirit, it was left at the end 

 of the operation of a greenish drab, which I suspect to be a mixture 

 of Ni 2 O 3 with Ni.O, although it may be Ni 2 O 3 changed only in ap- 

 pearance, for when treated with nitric acid no nickel is dissolved. 



15. Mn O 2 is changed at red heat into Mn 2 O 3 , which, with alco- 

 hol, ether, and pyroxylic spirit, continues the slow combustion very 

 steadily. A specimen of very pure Mn 2 O 3 acted extremely well, as 

 did also a portion of " euchrome " (a hydrated sesquioxide of man- 

 ganese (impure) dug from the estate of Lord Audley), after being 

 heated in the air to drive away the carbonaceous matter with which 

 it was mingled. Mn 2 O 3 will, if sufficient care be taken, catalyse 

 the moist gas arising from a strong solution of ammonia. 



16. Fe 2 O 3 , when in the state of a light puffy powder, catalyses the 

 vapour of ether, alcohol, and pyroxylic spirit, only requiring to be 

 heated on the gauze before it is laid over the capsule. It is cheap, 

 easily employed, and of invariable action. I have kept up the com- 

 bustion for several hours on a surface of 120 square inches. 



By means of a catalytic lamp in which the liquid employed is con- 

 tinually supplied from a reservoir and maintained at a constant level 

 in the capsule, I have used 7 or 8 square inches continuously during 

 thirty-six hours. This lamp I have occasionally used for laboratory 

 purposes, where a gentle and equable heat was required for several 

 hours. 



Pursuing my experiments with the oxides of the metals, heated 

 on wire gauze, I tried as many aa I could procure or make, and by 

 a tolerably wide induction I found that the sesquioxides have the 

 strongest tendency to produce and maintain the catalytic glow, and 

 do produce it in every case in which they are not decomposed by the 

 amount of heat required to begin the operation. 



When hydrated Fe 2 O 3 is heated and placed over alcohol, its colour 

 is deepened towards black, but not uniformly, and when cold the 

 original colour returns. But if it be made red-hot and quenched in 

 boiling alcohol out of contact with air, it is converted into hydrated 

 Fe 3 O 4 , and remains permanently a deep black magnetic powder, 

 soluble in acids. A strong solution of ammonia may be substituted 



