The Origin of Thermal Ionisation from Carbon

O. W. Richardson
1914 Proceedings of the Royal Society A  
In the ' Proceedings'* Dr. J. N. Pring describes interesting experiments designed to throw light on the origin of thermal ionisation from carbon. These experiments form a continuation of earlier experiments along similar lines by J. N. Pring and A. Parker.! In commenting on the results of the earlier work, Dr. Pring says:-" It has been shown by the present writer, in conjunction with A. Parker, that the ionisation which is produced by carbon at high temperatures, and in presence of gases at low
more » ... pressures, is reduced to a much smaller order of magnitude by eliminating impurities from the carbon, and by exhausting to a high degree the containing vessel. " The results throvj considerable doubt on the whole basis of the theory of electronic emission from incandescent solids. " According to this theory,! the ionisation produced by elements at high temperatures is due to the escape of free electrons, which pass into the surrounding space on account of the kinetic energy acquired at the high temperature. " It was shown, however, in the above work that in the case of carbon this ionisation is probably related to some chemical action or some inter mediate effect exerted by the gas in contact with the solid." In the summary and conclusions at the end of the later paper Dr. Pring states:-" It is clear from these results that the thermal ionisation ordinarily observed with carbon is to be attributed to chemical reaction betiveen the carbon and the surrounding gas. " While it is difficult to prove definitely that there is no electronic emission from the heated carbon itself, it is obvious that it is exceedingly small compared with ionisation which can be attributed to ordinary chemical change." The object of the present note is to point out certain conditions affecting the arrangement of apparatus used by these authors which make it quite certain, in the opinion of the present writer, that none of the statements
doi:10.1098/rspa.1914.0041 fatcat:hfsxym7lr5eelbgoahvs37ochu