and on the Isomeric Modifications of Selenium. 499 



sodium. But it was necessary to determine the value in water 

 of the calorimeter thus arranged. With this view, I made on the 

 calorimeter the determination of the calorific capacity of lead 

 between the surrounding temperature and that of boiling water. 

 As the specific heat of lead is known within these limits of tem- 

 perature, it was easy to deduce from the experiment the calorific 

 value in water of the calorimeter filled with naphtha. The fol- 

 lowing are the results of the experiment : — 



Weight of lead . . . 636^^-45 636^-45 



Specific heat of lead . . 0^^-03140 0^^-03140 



T 96° 77 97°-076 



6' 14°-165 ' 15°-085 



A^' 10°-1691 10°-1691 



Log A 2-2071712 2-2104166 



Mean of log A = 2-2087939. 



I wished to verify this value by an experiment made on the 



same mass of lead cooled in the refrigerating mixture : I obtained 



hence— p 636g'--45 



T -28°-030 



6' -f 6°-31 



A(9' 4°-2795 



LogA . . . . 2-1994784 

 I have assumed that the specific heat of lead between —28 



degrees and the surrounding temperatures was 0-0310. I 



found, in fact, — 



Between +15° and 98° 0-03140 (1) 



-78° ... +30° 0-03065 (2) 



and the mean 0-310 may be admitted as applying to the tempe- 

 ratures comprised between —28 and -1-7 degrees. 



The value of log A given by this experiment is a little less 

 than that furnished by the two preceding. I have adopted the 

 mean of the three values, that is 2-2056887. 



Here are the results which I obtained with sodium : — 



Sodium of M. Liebig. Sodium of M. Rousseau. 



t ^ > , ^ ^ 



I. II. III. IV. 



Weight of sodium 58^^-918 58^^-918 56«'--580 56«>--580 

 Weight of tinfoil 2g'-152 2»'-'152 2^^-700 2«''700 



T -34^-573 -30°-126 -29°-276 -21°-628 



6' 4°-7121 5°-0756 7°-242 7°-041 



A^' .... 4°-2787 3°-9356 3°-7913 3°-0315 

 c 0-29480 0-30267 0-29205 029742 



Specific heat of tin . . 0-0562. 



The experiments Nos. II. and IV. were made with cylinders 



