Prof. Daniell on a New Qxy-hydrogen Jet. 59 



produced with the greatest convenience and safety ; and that 

 upon a scale which it would not be prudent to adopt with 

 that instrument. When coal-gas is used, the change in the 

 colour of the flame indicates with great precision the exact 

 amount of oxygen which is sufficient to insure perfect com- 

 bustion; and by these means I readily effected the fusion of 

 100 grains of clippings of platinum into a perfect button, 

 with an expense of less than three pints of oxygen gas. The 

 aperture of the jet did not become, during the process, hotter 

 than the hand could bear. The combustion of the gases is 

 thus rendered so extremely manageable and ceconomical, that 

 I have not the least doubt that by the proper arrangement 

 of three or four such jets, the waste cuttings of platinum which 

 are formed during the working of that metal, and which at 

 present can only be worked up by redissolving them in acici, 

 might be readily melted together, and applied to profitable use. 

 I have succeeded in melting together a considerable quantity 

 of the grains of crude platinum, after digestion in nitric acid ; 

 but the button was perfectly brittle under the hammer. 



By placing the end of the jet b h within a lantern provided 

 with a parabolic reflector, and exposing to the flame upon a 

 pin of platinum a small fragment of lime, I succeeded perfectly 

 in exhibiting the beautiful experiment of Lieut. Drummond's 

 light; and can produce a prismatic spectrum almost equal in 

 brilliancy to the solar. By concentrating the rays of light 

 from the same source by means of the lenses of a solar micro- 

 scope, phosphorus may be inflamed, and chloride of silver 

 blackened ; affording a beautiful illustration of the conversion 

 of heat, which will not pass through glass into heat which will 

 pass through glass, with all the properties of solar heat, by the 

 radiating power of a solid undergoing no chemical change 

 whatever. 



The same jet when supplied with common air from the 

 gas-holder, instead of oxygen gas, serves the purposes of a 

 very convenient blowpipe ; and I have taken the opportunity 

 which this apparatus has afforded me, of trying upon a small 

 scale the experiment of heating the current of air which sup- 

 plies the combustion, upon the principle which has lately been 

 applied with such great success at the blast-furnaces of the 

 Clyde Iron-works, according to Mr. Dunlop's patent. 



For this purpose I connected the jet ba with a brass tube, 

 seven inches long, which I heated nearly to redness ; but upon 

 passing a current of air through it, it issued at the orifice at 

 a temperature, I think, below 300°. When the flame of coal 

 gas was supplied with this current, the temperature of a piece 

 ofplatinum exposed to it visibly exceeded the temperature 



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