Nitrogen Thermometer from Zinc to Palladium. 109 



This was calculated from the dimensions of the capillary. 

 The figures are given in Table I. This volume was reduced in 

 April, 1909, by bringing the manometer closer to the furnace, 

 since the water jacket of the furnace cut off the heat so com- 

 pletely that there was no risk in bringing the manometer as 

 close as possible (35 cm ). The volume v 1 was thereby reduced 



from 0-39 cc to 0*31 cc , and the ratio— from 0-00187 to 0-00150. 







The volume, "V, which enters into the correction term (see 

 page 102) was determined by weighing the bulb empty, and 

 filled with distilled water at a known temperature. A very 

 accurate determination of this volume was not necessary, the 

 important requirement being that the volume should not change 

 during a run. A check on change of volume was obtained in 

 the measurement of the value of p . The volume of the bulb 

 at 0°, up to the base of the capillary stem, was found to be : 



On 13 June, 1908 (new). 205-74 cc 



On 18 " " (after 1450°) 205'75 cc 



On 20 Apr., 1909 205*82 cc 



The volume of the unheated space, t\, was arbitrarily divided 

 into three portions for the convenient determination of its 

 average temperature, t x . The first portion, v/, extended from 

 the base of the stem to the top of the upper brick of the fur- 

 nace (see fig. 2) ; the second portion, y/', included the capillary 

 stem as far as the outside of the furnace ; the third portion, 

 v"\ extended to the surface of the mercury in the manometer 

 and included all of that portion of the unheated space which 

 remained at room temperature. 



The temperatures of the portions v{ and v/' were deter- 

 mined by placing a thermoelement at different points along the 

 stem during several of the runs. As this temperature does not 

 need to be known accurately, a few measurements gave a 

 sufficient indication of the distribution of temperature in the 

 portion of the "unheated space" within the furnace. 



A liberal estimate of the degree of uncertainty in the values 

 of v 1 and t l has been made and is included in Table I, together 

 with the effect which such errors would have on the calculated 

 temperature, t, at the copper point. 



Errors and Corrections inp \ — The same instrumental cor- 

 rections apply to p ' as toj/, but their proportional magnitude 

 is, of course, larger. The values of the uncertainty in t due 

 to these small errors will be found in Table IV. 



Changes in the value of p (the ice point) after heating to 

 high temperatures have always been disturbing factors in gas 

 thermometer measurements and have introduced uncertainties 

 of a very intangible kind. This was especially true of the 



Am. Jour. Sci. — Fourth Series, Vol. XXIX, No. 170. — February, 1910. 



