3 E. W. Morley — Amount of Moisture in a Gas. 145 



out of the six-bulb apparatus while the pressure has increased 

 from a to b. For this purpose put 



iv = the weight of the air which would pass through the con- 

 striction in the unit of time, if a perfect vacuum were 

 maintained on one side, and the barometric pressure on 

 the other. 



x = the pressure in the reservoir. 



h =the height of the barometer, assumed constant. 



t =the time. 



u =the weight of air in the reservoir at the pressure x. 



c =the capacity of the reservoir. 



I =the weight of a liter of air at the temperature and pressure 

 of the air during the experiment. 



V=the volume of rarefied air passing out of the apparatus 

 while the pressure rises from a to b. 



The weight of air passing out of the six-bulb apparatus in 

 the unit of time, when the pressure in the vacuum is not zero, 

 but x, may be written wf{x). At normal pressure, its volume 



would be yf(x), but under the pressure x, its volume would be 

 - -jf{x), and we therefore have dV=-—f(x)dt. Also it is ob- 



XI XL 



vious that j-=-j, so that du=—dx ; and obviously du = wf(x)dt. 



fC C6 ft 



cl 

 From the last two equations, we find dt=- — - — dx: and substi- 



hwj(x) 



dx 

 tuting this value we get dV=c — . 



x 



Therefore V = c / — = clog-. 



Jx=a x a 



This is the volume of rarefied air which passes the constriction 

 while the pressure rises in the reservoir from a to b. Its vol- 

 ume on entering is computed in an obvious manner. 

 I have so far made three experiments, as follows: 



1. 2. 3. 



Air entering apparatus = n 27 1. 23 1. 58 1. 



Mean temperature = t 16° C. 15° C. 19° 0. 



Air leaving apparatus .... 286 1. 228 1. 757 1. 



Excess leaving ._ 259" 205" 699" 



Liters an hour 16" l - 4" 1-2" 



Dilute acid, specific gravity 1-707 1-707 1-566 



Vapor tension of water from such acid at 



temperature t -48mm .43mm ] -85 mm 



Milligrams water taken) . 7 ._„,„ ,.„„ , ._„„ 



up by n liters air, at t \ COm P uted 13 ° 1(,mg 106mS 



18° 

 Specific gravity strong acid at — — 1-8381 1-8381 1-8388 



4 

 Loss, decimilligrams 5i 4-J- 18 



