284 abstracts: physics 



PHYSICS. — High-temperature gas thermometry. Arthur L. Day and 

 Robert B. Sosman; with an investigation of the metals by E. T. 

 Allen, Geophysical Laboratorj r . Publication No. 157, Carnegie 

 Institution of Washington. 

 The errors which have heretofore been present in measurements with 

 the nitrogen thermometer have been reduced by the present investiga- 

 tion to about one-fourth their former magnitude, and the certainty of 

 their evaluation is at least proportionately increased. 



The particular points to which most attention has been given are the 

 following : 



(1) To provide a uniform temperature about the bulb by a suitable 

 arrangement of electric-heating coils and diaphragms. 



(2) To enclose the furnace in a gas-tight bomb in which the pressure 

 outside the bulb can be maintained equal to that within for all tempera- 

 tures. This offers three distinct advantages: (a) it provides against 

 the deformation of the bulb through differences of pressure within and 

 without in the region of highest temperatures, where the bulb material 

 becomes softer; (b) by using the same gas within and without, there is 

 no tendency for it to diffuse through the bulb wall; (c) it enables the 

 initial pressure to be varied within considerable limits, thereby increas- 

 ing both the scope and sensitiveness of the manometer. 



(3) The expansion of the bulb material was determined with great 

 care and is probably accurate within 0.5 per cent. 



(4) The unheated space between the bulb and manometer has been 

 reduced until the total correction in this hitherto uncertain region 

 amounts to less than 4° at 1100°. An error of 5 per cent in the deter- 

 mination of its volume or temperature distribution is, therefore, prac- 

 tically negligible. 



It is probable that these changes serve to reduce the uncertainty 

 hitherto prevailing in the correction factors which require to be applied 

 to the gas thermometer in the region of 1100° to less than one-tenth of 

 its former magnitude. Furthermore, these improvements are equally 

 applicable throughout the region above 1100° as far as the present 

 measurements have extended (to 1550°). The chief source of the present 

 uncertainty is the temperature distribution over the surface of the 

 bulb in an air-bath. 



No effort has been made to prepare metals of exceptional purity in our 

 own laboratory, for the reason that such metals would not be available 

 for general use and would therefore be of little service. We have accord- 

 ingly adopted metals which are carried permanently in stock by dealers. 



In order to facilitate as far as possible the application of these results 



