146 Prof. D. Mendeleeff. On the Weight of a Cubic [Dec. 5, 



+ 0*1° {verve dur franc.) to +0*25° (ordinary easily fusible glass). 

 Expressing the temperature on the hydrogen thermometer scale as T 

 and using the latest determinations of Messrs. Thiesen, Maly and 

 Marek, Scheel, and Chappuis for temperatures from 0° to T = 30°, 

 I obtained* the following relation, which well satisfies the best 

 determinations : — 



< T - 4 > a (id 



122420 + 1130-2 T 



But the specific gravities of water, S*, we have to take according 

 to formula I and not II, as Messrs. Kupffer and Chaney give the tem- 

 peratures on the mercurial thermometer scale without reduction to the 

 hydrogen thermometer. As an illustration we give the following 

 comparison : — 



Mercurial thermometer (I). 



t = 10° C. S t = 0-999738 



t = 15° = 0-999152 



t = 16f° C. = 62° F. = 0-998890 



t = 20° , = 0-998272 



Hydrogen thermometer (II) . 



T = 10° C. S T = 0-9997308 



T s= 15° = 0-9991319 



T = 16f° C. = 62° F. = 0-9988681 



T = 20° = 0-9982348 



5. The weight of a litre of dry air, freed from carbonic acid at 0° and 

 a pressure of 760 mm., according to my deductionsf from the corrected 

 data of Messrs. Regnault, v. Jolly, Leduc, and Lord Rayleigh, is equal 

 to e = g 0-131844 + 0*0001 gram, where g is the force of gravity 

 in metres (accepted 9*8126 for London, 9*8100 for Paris, and 9*8188 

 for St. Petersburg). Assuming 0'04 per cent, of carbonic acid we 

 have for St. Petersburg, e = 1*2948, and for London, e 9 = 1*2940, 

 or at the aqueous vapour pressure in the air = h mm., the barometric 

 pressure at 0° = H, and the temperature t, I have assumed that the 

 weight of a litre of air : — 



— H— 0-37 h 



6 ~~ € ° 760 (1 + 0-00367 t) ' 



In all of the above mentioned assumptions we have certainly some 

 errors, but all of them taken together in the extreme case cannot 



* ' Bulletin of the Central Chamber/ &c., Part I, 1894, p. 86. 

 t Ibid. S 



