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XXVIII. Experiments on Carbon at High Temperatures and 

 under Great Pressures, and in Contact with other Sub- 

 stances. By the Hon. Charles A. Parsons*. 



THE primary object of these experiments was to obtain a 

 dense form of carbon which should be more durable 

 than the ordinary carbon when used in arc-lamps, and at the 

 same time to obtain a material better suited for the formation 

 of the burners of incandescent lamps. 



There were a considerable number of experiments made in 

 which the conditions were somewhat alike, and many were 

 almost repetitions with slightly varying pressures and tempe- 

 ratures. They may, however, be divided into two distinct 

 classes : the first, in which a carbon rod surrounded by a fluid 

 under great pressure is electrically heated by passing a large 

 current through it; the second, in which the liquid is replaced 

 by various substances such as alumina, silica, lime, &c. 



The arrangement of the experiment was as follows : — A 

 massive cylindrical steel mould of about 3 inches internal 

 diameter and 6 inches high was placed under an hydraulic 

 press ; the bottom of the mould was closed by a spigot and 

 asbestos-rubber packing — similar to the gas-check in guns ; 

 the top was closed by a plunger similarly packed ; this pack- 

 ing was perfectly tight at all pressures. In the spigot was a 

 centrally bored hole into which the bottom end of the carbon 

 rod to be treated fitted ; the top end of the carbon rod was 

 connected electrically to the mould by a copper cap which 

 also helped to support the carbon rod in a central position. 

 The bottom block and spigot were insulated electrically from 

 the mould by asbestos, and the leading wires from the dynamo 

 being connected to the block and mould respectively, the 

 current passed along the carbon rod in the interior of the 

 mould. 



The fluid was run in so as to cover the rod completely. 

 The plunger was then free to exert its pressure on the liquid 

 without injuring the carbon. The pressure in the mould was 

 indicated by the gauge on the press. 



Experiments. Class I. 



Among the liquids tested were benzene, paraffin, treacle, 

 chloride and bisuphide of carbon. 



The pressures in the mould during the several experiments 

 were maintained at from 5 to 15 tons per square inch ; the 



* From the Proceedings of the Royal Society, vol. xliv. Communicated, 

 with an additional note on Diamond Manufacture, by the Author. 



