Mr. E. Solly on a Chemical Lamp-Fur7iace. 1 93 



this causes the heated air to pass round the upper edges and 

 over the lid of the crucible, so as to bring the whole to the 

 same temperature. 



With this arrangement it is easy to keep a platinum cruci- 

 ble two inches high and an inch and a halt* across at a bright 

 red or yellow heat for any required time; the heat is perfectly 

 manageable, the gas may be turned off at any moment, and 

 as quickly lighted ; hence any operation is far more under 

 control than in a furnace. The heat obtained with a cru- 

 cible of the size just mentioned is rather above the melting- 

 point of silver, for a piece of that metal is easily fused in a 

 porcelain crucible placed in the interior of the platinum one. 

 It is of course equal to the fusion of mixtures of silicates with 

 carbonate of soda, three or four hundred grains of a mixture 

 of carbonate of soda and a siliceous compound being perfectly 

 fused in about eight minutes, whilst from the entire command 

 at all times had over the source of heat, it is easy to moderate 

 it when the evolution of carbonic acid is too rapid, and to 

 stop it as soon as the operation is complete ; in fact, the pro- 

 gress of the experiment may be watched from the commence- 

 ment to the end with the greatest facility. 



The object which I had originally in view in the construc- 

 tion of this lamp, was to obtain a cheap, simple and effica- 

 cious method of heating a platinum crucible to bright redness 

 without exposing it to the contact of solid fuel, and in this 

 the attempt was perfectly successful. The decomposition of 

 earthy silicates may, it is true, be very easily effected in an 

 ordinary furnace; the crucible being protected from contact 

 with the fuel by placing it in an earthen one, or by wrapping 

 it in a thin piece of platinum foil, which preserves the crucible 

 very perfectly from the action of the fuel in a cheap and very 

 convenient method ; but still, the above lamp-furnace is de- 

 cidedly superior to that or indeed any other mode I have 

 tried. Independent even of the question of oeconomy, I prefer 

 it to the Argand spirit-lamp. 



As the use of such a lamp must in part depend on its sim- 

 plicity, I was anxious not to complicate it more than was 

 absolutely necessary; but I have no doubt that its power 

 might be very greatly augmented ; in its present state, how- 

 ever, it is useful for several purposes besides the mere ignition 

 of a crucible, such as, for example, glass-blowing and bending 

 large or thick tubes ; in fact, in all cases where a bright red 

 or yellow heat is required, and where an ordinary furnace is 

 inapplicable. 



