320 



Hon. Charles A. Parsons. Experiments on [June 14, 



VIII. "Experiments on Carbon at high Temperatures and under 

 great Pressures, and in contact with other Substances." 

 By the Hon. Charles A. Parsons. Communicated by the 

 Right Hon. the Earl of Rosse, F.R.S. Received June 13, 

 1888. 



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 temperatures. They may, how- 

 ever 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 a 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 packing 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 con- 

 nected 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 tbe 

 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 bisulphide of carbon. 



The pressures in the mould during the several experiments were 

 maintained at from 5 to 15 tons per square inch ; the initial size of the 

 rod was in all cases J-inch, and the current from 100 to 300 

 amperes. 



