FURNACE REACTIONS UNDKR Hlcil <:. \sEOUS PRESSURES. 437 



keep ln-|ci\v the explosive limit, a small air. l>eing maintained to effect the combination. 

 Under these conditions, however, the water vapour produced was rapidly converted 

 into carlxHi monoxide and hydrogen under the action of the arc. The method had, 

 therefore, no advantage over the direct combustion by carbon, and was al>andoned. 



In many of the cases in which a carbon arc was maintained after all the oxygen of 

 the air had been fixed, small traces of hydrocyanic acid were detected. In the above 

 experiment, in which hydrogen was present in considerable amount, the formation was 

 much increased.* 



| 



ON THK FORMATION OF CALCIUM CARBIDE. 



The production of calcium carbide, constituting a simple and typical example of 

 electric furnace reactions, was considered a suitable subject for the first series of 

 experiments. 



From previous experience we were impressed with the necessity of maintaining the 

 greatest possible uniformity in the conditions under which the furnace was operated. 



Above all it was desirable to avoid the variations introduced by the use of different 

 forms of furnace construction, and therefore for all the experiments dealt with in this 

 section we have employed the simple type represented in fig. 11, A, the dimensions 

 of the furnace, the size of the electrodes, the weight and constitution of the reacting 

 mixture l>eing kept the same and, as far as possible, the factors under consideration 

 varied only one at a time. 



The building up of the furnace entailed the use of the enclosure iu a vertical 

 position as shown in Plate 6, fig. 1. The furnace cover having been removed, by 

 means of a crane installed for the purpose, the cast-iron liner is raised and deposited 

 on a separate stand where it is prepared for the experiment. To protect the bottom 

 of this receptacle from the direct action of the arc, a layer of powdered retort carlxm 

 is first introduced, which thus constitutes the lower electrode. The mixture of lime 

 and carbon (about 10 kilogs.) is then filled up around a paper tube which serves to 

 keep a central passage free for the upper electrode. 



If there is any doubt as to the perfect desiccation of the raw materials, the cast- 

 iron pot with its contents must be maintained at a red heat for some hours before it 

 is placed in the enclosure. This not only ensures more consistent results, but renders 

 it possible to follow the progress of the reaction by a measurement and examination 

 of the gases generated. The cover of the enclosure is lowered carefully into position, 

 the carbon electrode sliding into the cylindrical space which has been reserved for it. 



After the bolts have been tightened up and the desired quantity of gas introduced, 

 the arc is started by lowering the upper electrode, which then comes in contact with 

 the carbon lied beneath it. 



* H. HOYKRMANN, ' Chcni. Zeitung,' 190:.', vol. 28, pp.70, 71 : .1. URTS/KIKWIC, '%. fur Klektrochwnie,' 

 1903, vol. 9, pp. 83-5 ; H. AuKR, ' Acad. Sci. Buda-Pesth,' 1904. 



