998 



manometer-tube is sun-oiiiided (see tig. 4) by a copper enclosure forming 

 the continuation of the chamber by piling up, as far as the mercury 

 reaches, a number of mutually fitting pieces of copper tubing 

 consisting of hinging halves. One of them carries a thermometer 

 in a copper tube soldered to the main piece. 



It is of special importance to know the noxious vohime with great 

 accuracy '). All its parts are calibrated in the manner detailed on 

 previous occasions '), whereas the spaces at the soldering places of 

 the steel capillar}- to the glass capillary are known by measuring 

 and estimating the various dimensions. Moreover a volumenometric 

 determination was made by sealing the steel capillary at the thermo- 

 meter-end, tilling the adjustment-space and capillary with dry air and 

 utilising the calibration-tap /v^A/ mentioned in note 1 p. 992. ') The two 

 results^ by the direct measui-ement and weighing and by this volu- 

 menometric determination of the volume of the adjustment-space 

 between a horizontal plane through the adjustment-point and the 

 sealing-place of the thermometric capillary agree within a few mm'. 



The measurements with the present thermometer") are carried out 

 in the same manner as before with the previous types of instrument 

 (see particularly Comm. N°. 141a). 



The correction for the capillaiy of the thermometer is obtained 

 by mounting the wider capillary of an auxiliary thermometer beside 

 the capillary in question, according to the method used by Chappuis. 

 (See fig. 1)' 



§ 3. Apparatus and method. Fig. 3 gives a general aspect of the 



1) It is possible in the manner followed by Hknnfng, Ann. d. Phys. (4) 40 

 1913) p. 635 to free the measurements of the temperature from an error which 

 (as in his measurements) remains in the determination of the noxious space, by 

 not using the real pressure-coefficient in calculating a certain range of tempera- 

 tures, but tliat one which is found by calculation with the incorrect value of the 

 noxious space, but it is very mucli preferable to prevent errors of that kind by 

 a careful determination of the noxious space, which as a matter of fact does not 

 involve any special difficulties. 



') In computing the space between a horizontal plane passing through the adjust- 

 ment-point and the surface of the mercury the formulae of Lohnstein and of 

 Scheel and Heuse were used. For the determination of the section of the tube at 

 the place of adjustment, a temporary glass tap was blown to the lower end of 

 the adjustment-tube. 



') In this measurement the steel capillary was surrounded by a copper tube to 

 make sure of the temperature. 



*) The data of the thermometer are as follows: Volume of thermometer-bulb 

 108-31 cm^ ; volume of glass capillary -040 cm^ ; noxious space -767 ± '003 cm' 

 diameter manometer-tube 1-473 cm.; change of volume of bulb for 1 atm. change 

 of pressure 0051 cm'. 



