112 



DRS. J. A. BARKER AND P. CHAPPUIS ON A 



APPENDIX I. 



With a view to facilitating the calculations involved in platinum thermometry, we 

 give, as an appendix, several tables calculated by Mdlle. DE BAULLER and M. MAUDET, 

 of the Bureau International, which have proved of great utility during our work. 



Krp \ j T "1 



Too) ~~ 100 r and the P roduct 



of this quantity into a number of different values of 8. It is used for deducing pt from 

 given values of T. 



Table II. is for the resolution of the converse problem, and gives T corresponding 

 to different values of pt for thermometers having a 8 between 1'54 and 1'57. At the 

 side are given differences for interpolation between the whole degrees. 



Table III. is for the reduction of the steam points, and is extracted from the table 

 calculated by M. BROCH from the results of REGNAULT for the boiling-point of water- 

 under different pressures. 



Table IV. is for reducing to its equivalent in mercury pressure the excess of 

 pressure of the steam in a boiling-point determination, as measured in millimetres 

 of water. 



Table V. is for converting to the platinum scale the temperature of the steam as 

 obtained from Table III. 



As an example of the use of some of these tables, we give the following : 



Let the resistance in ice of a certain platinum thermometer whose 8=1 '500 be 

 2'57827 ohms, and let its resistance in steam be 3'57298 ohms, the barometric height 

 at the time, corrected for temperature and reduced to sea level and latitude 45, being 

 749 '96 millims., and the excess of the steam pressure over that of the atmosphere 

 being 1'8 millim. of water. Find the resistance corresponding to 100. 



From Table IV. the mercury pressure corresponding to 1'8 millim. of water = 0'13 

 millim. Adding this to the barometric height we obtain 750'09 millims. as the total 

 pressure of the steam. Then from Table III. we obtain, as the temperature of the 

 steam at this pressure, 99'6343. 



For 8=1 "500 we find from Table V. that the platinum temperature corresponding 

 to 99'6343 is 99'6343 + 0'0055 = 99'6398. 



