ACETYLENE. 789 



and production of high pressures and heat accounting for the 

 various volcanic disturbances and the large natural deposits of 

 petroleum and other carbonaceous material, which occur so abun- 

 dantly in some districts. 



Pure calcium carbide has a specific gravity of 2"262 ; in a dry 

 atmosphere it is odorless, but upon exposure to moisture evolves 

 the peculiar odor of acetylene. When exposed in lumps to the 

 action of ordinary air it becomes coated with a layer of hydrate 

 of lime, which protects the interior of the mass from further oxi- 

 dation. It is not inflammable, and can be exposed to the heat of 

 the ordinary blast furnace without decomposition. It is, in fact, 

 a very stable compound, its ready decomposition under the action 

 of water being quite at variance with its other chemical proper- 

 ties. It was first prepared by Woehler, in 1863, by fusing an alloy 

 of zinc and calcium with carbon. He called it acetylene carbide. 

 It forms a dark grayish or red dense mass, which upon fracture 

 shows a crystalline metallic surface. The whole process of manu- 

 facturing acetylene, from the preparation of the lime and coke 

 onward, is very simple, and the only reason why it is new as a 

 commercial product is the difficulty of causing a combination be- 

 tween the calcium of the lime and the carbon of the coke. Noth- 

 ing short of the temperature of the electric furnace (3500° to 

 4000° C.) will bring this about, and the comparative modernness 

 of this apparatus accounts for the lateness of the calcium carbide. 

 The chemistry of the process is as follows : Quicklime (CaO) and 

 coke, or any other substance whose main content is carbon (C), 

 are mixed and fused together in the electric furnace. The cal- 

 cium (Ca) of the lime combines with part of the carbon (C) of 

 the coke to form calcium carbide (CaC2) ; the oxygen (O) of the 

 quicklime combining with another portion of the carbon to form 

 carbonic oxide : 



CaO + 3C = CaCs + CO 



Quicklime. Coke. Calcium Carbonic 



carbide. oxide. 



Carbonic oxide is a gas and is driven off, leaving calcium car- 

 bide and the various impurities in the furnace. The further re- 

 action to form acetylene occurs when calcium carbide is subjected 

 to the action of water : 



The following description of the commercial manufacture of 

 calcium carbide as conducted at Spray is based on a paper by G. 

 de Chalmot, who for some time had personal supervision of the 

 works of the Wilson Aluminum Company at Spray, N. C, and 



