124 M. Deville on the production of high Temperatures. 



earthen crucible becomes as liquid as glass. This arises frotti the 

 impurities accompanying the clay, for the silicates of alumina, 

 especially those containing an excess of alumina, do not melt easily. 

 In one experiment, Deville found that platinum was melted at a 

 temperature at which topaz was not attacked. Deville used 

 crucibles of quicklime, which are simply cut with a knife from 

 pieces of lime well baked and slightly hydraulic. For certain 

 experiments he used crucibles and tubes of carbon, cut in a lathe 

 from the graphite of gas retorts. They may be purified by passing 

 a stream of chlorine over them while heated to redness. This 

 deprives the graphite of the sulphur, iron, sihca, and alumina, 

 which are converted into the chlorides and volatilized. Crucibles 

 of alumina are also used for certain operations. 



With this furnace Deville has succeeded in melting many 

 substances of the most infusible nature. Platinum melts in a 

 lime crucible, and has then properties very different to those of 

 the ordinary metal. Ordinary platinum may be shown to be full 

 of minute holes ; the melted platinum is quite free from these : 

 melted platinum does not determine very readily the union of 

 hydrogen and oxygen ; it has great malleability and ductility. 

 When the heat is raised a little above the melting-point of plati- 

 num, it volatilizes with great facilitj\ When the experiment is 

 made in two crucibles, both hermetically sealed, there is found 

 on the cover of the outer crucible a multitude of little globules 

 of platinum, some as large as a pin-head, others only to be seen 

 with the lens, and presenting very much the appearance of the 

 globules of mercury obtained in blowpipe analyhis. 



Metallic manganese is obtained by mixing pure peroxide with 

 a quantity of sugar-charcoal not quite sufficient for its complete 

 reduction, placing the mixture in a lime crucible which is enclosed 

 in another and heated under certain precautions. 



The metal is found united to a regulus, and surrounded by a 

 reddish-\ iolet crystalline mass, which may be a spinelle ef man- 

 ganese and lime, Mn^ 0^, CaO. The metal is pure ; it contains 

 no carbon, having been melted in an excess of oxide. It has 

 a rose-coloured reflexion like bismuth, and is brittle like that 

 metal, although it is very hard. Its powder decomposes water 

 at a point a little above the ordinary temperature. 



Chromium was obtained by melting pure oxide of chromium 

 with a quantity of carbon insufficient for complete reduction. 

 It was melted, but not to a regulus, although the heat employed 

 would have fused and volatilized platinum. Chromium cuts 

 glass like diamond; it is about as hard as corundum. It is 

 attacked by hydrochloric acid, but not by nitric acid, whether 

 dilute or concentrated. 



Nickel is obtained like manganese ; it melts to a very homo- 



