Temperature on the Specific Heat of Aniline. 53 



Great care is required to accurately determine the fixed 

 points of such thermometers. For example, a difference of 1° 

 at 100° C. made a difference of '067835 ohm: thus a difference 

 of 1 millim. on the barometer caused a difference of '00244 

 ohm. Readings of the pressure were taken on a standardized 

 j-inch diameter mercury-barometer, and also on a compen- 

 sated sulphuric barometer suspended beside it. It was found 

 that the observations, if corrected to 100° 0. by the pressure 

 as deduced from a mercury-barometer, were not in close 

 agreement ; but if by the sulphuric-acid barometer, the 

 results were satisfactory. On examination it appeared that 

 the first observations of each series, when corrected for pres- 

 sure, were in harmony whichever barometer was used ; but 

 such was not the case with subsequent ones of the same series. 

 The cause is, I believe, to be found in the necessary handling 

 of the barometer that takes place when adjusting the mercury 

 to the ivory point. The temperature within the case under- 

 goes a change, and the indications of the thermometer usually 

 placed within the metal tube surrounding the barometer give 

 but little information as to the real temperature of the mer- 

 cury column, whereas the sulphuric-acid barometer requires 

 no manipulation and is independent of such temperature 

 changes. As an example of the consistency of the boiling- 

 point when corrected by the H 2 S0 4 barometer, I give the 

 following consecutive results :— - 



(Difference in R for 1° C. at 100° = '067835.) 



Date. 



K after 

 correction 

 for tempe- 

 rature of 

 box, plug 

 errors, &c. 



Barometer 

 corrected 

 to sea-level, 

 lat. 45° and 

 temp. 0° 0. 



Boiling- 

 point. 



Correction 

 to 100° C. 



(at 100° 0.). 



Thermometer AB. 



June 3 ... 



„ 5 ... 



July 7 ... 



24-58798 

 24-57187 

 24-58336 



761-10 

 754 67 

 759-25 



100 040 



99-802 

 99-972 



- -00271 

 + ■01342 

 + -00190 



24-58527 

 24-58529 

 24-58526 



Thermometer CD. 



June 3 ... 



„ 5 ... 



July 7 ... 



24-58306 

 24-56961 

 24-58163 



76110 

 754-52 

 759 34 



100040 

 99-796 

 99-975 



-00271 



+ -01383 

 + -00168 



24-58335 

 24-58344 

 24-58333 



