450 DR. CHARLES H. LEES ON THE EFFECT OF TEMPERATURE ON THE 



Standardisation of tin- Measurement*. 



TemiM'ratni'1 1 Measurements. The No. 40 platinum wire of the spirals used in the 

 temperature measurements was obtained from Messrs. JOHNSON and MALLY specially 

 for platinum thermometer work. In order to determine whether the resistance of the 

 spirals was normal they were tested twice during the course of the work in steam 

 ice, and liquid air, and the " fundamental constants " of CALLENDAR* calculated. 



As stated on pp. 436, 437, one end of each spiral was soldered to 92 centims. of No. 20 

 copper wire, and both the other ends to a third copper wire of the same length and 

 diameter. The glass tubes carrying the coils were inserted in an ordinary boiling- 

 point apparatus as used for thermometers, and the copper leads brought to 

 the terminals of a standard resistance box. The connections could l>e made 

 to the ends AB, AC, or CB (see fig. 7). If RAB, RAC, and RC B are the three 

 resistances observed, the resistances of the coils themselves are R AB RCB 

 and RAB RAC respectively. The apparatus was then placed in crushed ice 

 and finally in liquid air contained in a Dewar tube and the measurements 

 repeated. The temperature of the liquid air was read on a petroleum 

 Fig- ^ ether thermometer which had been standardised at the Reichsanstalt. One 

 of the two tests which gave almost identical results is given below. 

 Determination of "fundamental constants" of platinum coils 03.12.9. 

 Resistances determined on standard box with ratio 1000 : 10 throughout. 

 Barometer, corrected 73 '60 centims., therefore boiling-point = 99'10 C., 

 In steam at this temperature, 



RAC = 1-9170, R CB = 1'9061, R AB = 37657 ohms. 



Hence coil in AC = 1'8596, coil in CB = 1-8487 ohms at 99'l C. = 372'l abs. 

 In ice at C., 



R AC = 1-4025, RCB = 1-3941, RAB = 27474 ohms. 



Hence coil in AC = 1'3533, coil in CB = 1-3449 ohms at C. = 273 abs. 

 In liquid air at 186'5 C. 



R AC = -3699, RCB = '3645, R AB = '6937 ohms. 



Hence coil in AC = '3292, coil in CB = '3238 ohms at -186'5 C. = 86'5 abs. 

 Hence we have, using CALENDAR'S nomenclature : 

 " Fundamental interval " 



1-8596-1-3533 



for AC coil = - = '5109, 



'99 1 



., 1-8487-1-3449 

 for CB coil = - = '5084. 



* ' Phil. Mag.,' XLVIL, p. 197, 1899. 



