444 MESSRS. R. S. HUTTON AND J. E. PETAVEL ON ELECTRIC 



ON THE FUSION or SILICA. 



When quartz is subjected to a high temperature it attains the vitreous condition 

 and becomes sufficiently plastic to be moulded and shaped. 



It was shown some years ago that silica can be heated in direct contact with carbon 

 and brought to a plastic state without marked reduction occurring. 



The heating was effected either by radiation from an electric arc or by placing the 

 material around a carbon core* through which the current was passed. 



At ordinary pressures it is, however, impossible to maintain any considerable 

 quantity of silica in a really liquid state. 



When the power expenditure in the core is increased a rapid volatilisation sets in 

 which effectually puts a limit to the temperature. 



It seemed probable that more satisfactory results could be attained by carrying out 

 the fusion under a considerable pressure in the enclosure described above. 



Details of the principal experiments will be found in Table V. A resistance 

 furnace of construction similar to that shown in fig. 11, B, was first employed, the 

 central core of granular carbon being replaced by a carbon tube held in two massive 

 graphite terminal pieces to which the current was led. This core was arranged 

 centrally and surrounded by pure quartz sand, the experiments being carried out in 

 air at 50 and 100 atmospheres. 



Thick-walled hollow cylinders, 25 centims. long and 15 or 20 centims. external 

 diameter, were in this way easily obtained. 



At first sight more complete liquefaction seemed to have occurred. Upon fracture, 

 however, the material was found still to contain innumerable small gas bubbles, 

 giving it a translucent appearance and tending to show that the fluidity had not been 

 much increased. 



Proof of the diminished volatilisation of the material was, however, given by 

 the absence of a deposit of condensed silica vapour, as also by the very small 

 formation upon the core of carborundum, both of which are evident at atmospheric 

 pressure. 



It was then decided to study two modifications of the regime, either of which 

 seemed likely to give improved results. 



The well-known ease with which hydrogen passes through heated silica led us to 

 believe that if a compressed atmosphere of this gas were employed any bubbles 

 imprisoned at the moment of fusion would disappear, leaving the glass clear. None 

 of our experiments, however, verified this assumption. Not only is the occlusion of 

 the gas apparently unaffected, but from the nearly explosive violence with which the 



* HUTTOX, 'Mem. Manch. Lit. and Phil. Soc.,' 1901, vol. 46, No. 6, pp. 1-5; also 'Trans. Amer. 

 Electrochem. Soc.,' 1902, vol. 2, pp. 105-111. 



