530 On the Psychrometer and Chemical Hygrometer 



Table IV. 



Experiment. 



Chemical 

 method. 



Psychrometer. 



Glaisher. 



Haeghens. 



Guyot. 



Wild. 



1 



millim. 



743 



915 



8-99 



8-78 



10-70 



7-63 



12-15 



9-9L 



8-90 



10-00 



11-82 



10-23 



millim. 

 7-76 

 9-55 

 9-00 

 8-99 



10-72 

 7-78 



11-72 

 965 

 8-68 

 952 



11-84 

 9-67 



millim. 

 7-37 

 9 54 

 8-88 

 8-74 



10-75 

 7-39 



11-78 

 957 

 8-45 

 9-38 



1193 

 9-55 



millim. 

 731 



9-51 



8-87 

 8-77 



10-76 

 734 



11-80 

 9-57 

 8-43 

 9*41 



11-93 

 9-57 



millim. 

 74 

 95 

 8-9 

 88 



10-7 

 7-4 



117 

 96 

 8-5 

 94 



119 

 9-5 



2 



3 



4 



5 



6 , 



7 



8 



9 



10 



11 



12 





Mean 



964 



9-57 



9-44 



9-44 



944 





Regnault*, during his comparative experiments with the 

 psychrometer and his chemical hygrometer, made a series of 

 determinations in which the temperature of the air was below 

 the freezing-point. The experiments were made in December 

 1846 and January 1847. The lowest temperatures during 

 the sixteen determinations were — 6°"89C. for the dry-bulb 

 and -7°-74 for the wet-bulb ; the highest -0°'13 and -0°*69 

 respectively. The chemical determination lasted from three- 

 quarters of an hour to one hour ; readings of the psychrometer 

 were taken every five minutes. 



The results showed variations of the psychrometer over 

 the chemical method ranging from +11 per cent, to —3 per 

 cent., the mean being about +4 per cent. 



In conclusion I must express my hearty thanks to Mr. 

 Stone, the Radcliffe Observer, who has given me every facility 

 to make these and the previous experiments, and has always 

 aided me with his advice. I must also thank his assistants, 

 Messrs. Wickham, Robinson, and Maclean. 



Annates de Chimie et de Physique, t. xxxvii. 1853, p. 274. 



