272 REPORTS ON THE STATE OF SCIENCE. 



3 The flask or bottle containing liquid ether to be vaporised by the 

 current of air should be double, and provided with taps allowing the 

 air to be driven into the balance-case, through either bottle alone or 



If, instead of 1,000 c.c, the flask (or bulb) measures v c.c. 

 _ m 1000 

 P ~ 202 X ~" 

 If the temperature is T instead of 0° (273 aba.), 



m 1000 T 



F ~ 20 T 2 X ~v~ 273* 



If the barometer is B instead of 760 mm. Hg, 



to 1000 T 760 

 P_ 20 : 2^r X 273 X 3" 



log P = log to + log 1000 + log T + log 760 



- log 20-2 - log v - log 273 - log B 

 = log w + 3 + log T + 2-8808 



— 1-3054 — log v — 2-4362 — log B 



or 



log P = 2-1392 + log to — log v + log T - log B . . . (1) 



By means of this formula it is easy, if required, to correct readings for temperature 

 and pressure, or to calculate what volume v must be given to a bulb in order to 

 afford convenient scale readings at average temperature and pressure. Taking these 

 as being 18° and 760 mm., the formula becomes : — 



log P = 2-1392 + log m - log v + log (273 + 18) - log 760 



= 1-7223 + log to- log v (2) 



The application of this simplified formula is best illustrated by examples :— 



Question. What should be the capacity v of a bulb to indicate units per cent, of 



ether by centigramme increments of weight at normal temperature ( ] 8°) and pressure 

 (760 mm. Hg) ? 



Answer.— log 1 = 17223 + log 10 - log v 

 or log v = 2-7223 

 or v = 515 - 6 c.c. 



Question. What is the weight to indicating 8 per cent, of ether with a bulb of j> 



capacity = 230 c.c. at normal temperature (18°) and pressure (760 mm. Hg) ? 



Answer.— log 8 = 1'7223 + log to - log 230 



0-9031 = 1-7223 + log to - 2-3617 



log to = 15425 



to = 34-87 



The analogous formulae for chloroform — 1, for correction of readings ; 2, for 

 calculation ofv and to at average temperature and pressure— are 



log P = 1-8377 + log to - log v+ log T- log B ... (1) 



and 



log P = 1-4208 + log to — log v (2) 



The litre- weight difference between ether-and-air (2-020) is almost exactly half 

 that between chloroform-and-air (4-045). So that a given bulb graduated for 

 chloroform in units per cent, is graduated for ether in double units per cent., and 

 for all practical purposes the same bulb and balance can be used for ether and for 

 chloroform. 



