Chemistry and Physics. 239 



steel. It may be prepared by heating the components to 3000° in 

 the electric furnace and pouring the mass into water. Diamonds 

 are formed where great pressure exists in the interior of the 

 regulus, and well crystallized Fe 3 C can be separated from the 

 product by dissolving the metallic iron in dilute acid. If the 

 product be slowly cooled, the greater part of the carbon sepa- 

 rates as graphite and ordinary cast-iron results. The carbides of 

 chromium, molybdenum, tungsten, vanadium, zirconium and tita- 

 nium are all well-crystallized substances produced by means of 

 the electric furnace, and in general they are very stable in their 

 behavior with acids, etc. 



The carbides which are decomposed by water are, Li a C 2 , K 2 C 2 , 

 Na 2 C 2 , CaC 2 , SrC 2 , BaC 2 , CeC 2 , LaC 2 , PrC 2 , NdC„, SaC 2 , YC 2 , 

 ThC 2 , A1 4 C 3 , Be 2 C, Mn 3 C and U 2 C 3 . Sodium and potassium car- 

 bides are prepared by the action of acetylene gas upon the 

 metals. They are decomposed at high temperatures, hence they 

 cannot be prepared by the electric furnace method. On the 

 other hand, the other alkali-metal, lithium, forms a carbide at 

 high temperatures. This is transparent and well crystallized. 

 The alkali-metal carbides and also those of calcium, strontium 

 and barium yield acetylene, C 2 H 2 , when they are treated with 

 water. It is calcium carbide which is extensively used for the 

 preparation of this gas. The commercial product is dark in 

 color from impurities, but when pure it is transparent and color- 

 less. Aluminum and beryllium carbides can be prepared by 

 means of the electric furnace ; both of these give methane, CH 4 , 

 with water, according to the following equations : 



A1 4 C 3 + 12H 2 = 3CH 4 + 4A1(0H) 3 

 Be 2 C + 4H 2 0= CH 4 + 2Be(OH) 2 . 



The carbides decomposable by water, that have been men- 

 tioned, give off a single gas, either acetylene or methane, when 

 thus decomposed, but the others produce more than one product. 

 Manganese carbide gives methane and hydrogen as follows : 



Mn 3 C + 6H 2 = CH 4 + H 2 + 3Mn(OH) 2 . 

 Uranium carbide gives a mixture of acetylene, ethylene, 

 methane and hydrogen ; cerium and lauthanum carbides give 

 mixtures of acetylene, ethylene, methane, and some liquid and 

 solid hydrocarbons ; yttrium, neodymium, praseodymium, sama- 

 rium, and thorium carbides give acetylene, methylene and 

 methane, and in some instances hydrogen also. 



Certain metals, such as gold, bismuth, and tin, dissolve no car- 

 bon in the electric furnace, while copper dissolves very little. 

 Silver dissolves some carbon at the temperature at which it 

 evaporates, but most of this separates upon cooling. The plati- 

 num metals dissolve carbon readily at high temperatures, but it 

 separates as graphite when the metals solidify. 



Moissan advances the theory, somewhat similar to one pro- 

 posed bv Mendeleeff many years ago, that petroleum, in some 

 has been produced from carbides. He believes that 



