388 A New and Curious variety of Combustion. 



plunging a piece of this sponge in a mixture of two parts 

 hydrogen and one oxygen, explosion of course ensues; but 

 if the proportions of the mixture be very different from that 

 which forms water, or if a gas, foreign to the combination, 

 be present, such as azote, the combination takes place slow- 

 ly, the temperature rises a little, and water is soon conden- 

 sed upon the glass. 



Platina sponge strongly calcined, loses the property of be- 

 coming incandescent, but in this case it produces slowly and 

 without any sensible elevation of temperature, the combina- 

 tion of the two gases. Platina reduced to fine powder, has 

 no action at common temperatures, nor has it in the form of 

 wire or plates. But the French chemists, state, that 

 when reduced to leaves as thin as the metal will admit, 

 it acts at common temperature, and acts upon the mixed 

 gases, with a rapidity proportionate to its thinness, in 

 some insstauces causing detonation. But one thing is re- 

 markable, viz, that a very thin leaf of platina, rolled upon a 

 glass cylinder, or suspended freely in a detonating mixture, 

 produces no sensible effect, though exposed during several 

 days ; but the same leaf compressed into a wad, acts instant- 

 ly, and produces detonation. 



Leaves and wire too thick to produce any action, 

 when cold, will nevertheless, as Sir H. Davy had before 

 determined, act at the temperature of 2 to 300°, according 

 to their thickness. Palladium acts as well as Platina at 

 the same temperature, and thickness. Rhodium occasion- 

 ed the formation of water at 240°. 



Gold and Silver in thin leaves act only at elevated tem- 

 peratures, but always below that of boiling mercury. Sil- 

 ver is less efficacious than Gold. 



Other gaseous mixtures were acted upon by the same 

 means, oxide of carbon and oxygen combined. Nitrous 

 •gas was decomposed by hydrogen, at common tempera- 

 tures, by platina sponge, forming water, and ammonia; 

 olefiant gas mixed with a proper quantity of oxygen, is 

 completely transformed into water and carbonic acid. 



It is well known that iron, copper, gold, silver and plati- 

 na have the property of decomposing ammonia at a certain 

 .temperature, without absorbing either of its principles, and 

 that this property appears inexhaustible. Iron is more effi- 

 cient than copper, and copper more than silver, gold orpla- 



