CARBON DIOXIDE AT DIFFERENT TEMPERATURES. 20 1 



altered to about half its original value, and if the electric current is adjusted so that 

 the rise in temperature of the gas is the same as before, 



C I E I = JSQ, 80+^80, ......... (2) 



where the letters with suffixes refer to the new values of the corresponding quantities 

 in (1). From (1) and (2) h may be eliminated, leaving an expression for S which 

 does not involve the heat loss. 



The rates of flow of the gas were obtained by passing it through sixteen fine metal 

 tubes arranged in parallel, and measuring the pressure difference between their ends, 

 the absolute pressure at one end, and their temperature. The expression giving the 

 rates of flow in terms of these quantities was obtained from the results of a separate 

 series of experiments. 



In the experiments on the specific heat of air the gas was pumped continually 

 through the apparatus by a bellows, worked by an adjustable crank driven by a 

 wheel which was connected to a motor. This part of the apparatus was placed at 

 the far end of the room, and the motor was turned in such a direction that it did 

 not affect the needle of the galvanometer which was used with the platinum ther- 

 mometers. The gas passed from the bellows to a sulphuric acid dryer, consisting of a 

 wide glass tube about 1 metre long, half filled with pure strong sulphuric acid, and 

 strapped to a board which was fixed to the floor by two brass springs, so that the 

 tube could rock parallel to its axis. The rocking caused a constant renewal of the 

 surface of the acid, and was brought about by connecting the board by means of a 

 steel wire to the top of the bellows. The acid was renewed daily during the experi- 

 ments. The gas passed from the sulphuric acid dryer into a Wolff's bottle, which 

 served to collect any sulphuric acid spray, and thence to the towers BB, fig. 2, 

 through a piece of composition tubing and the T-piece A, which was open to the 

 atmosphere through a piece of rubber tubing partially constricted by a clip. The 

 flow of the gas through the apparatus could be roughly adjusted by allowing some of 

 it to escape into the atmosphere. The first of the towers BB contained solid KOH 

 to remove any carbon dioxide, sulphuric acid, or water vapour remaining in the gas, 

 and the second contained calcium chloride. The gas passed from the towers through 

 a cotton wool dust filter C to an automatic pressure regulator D, to be presently 

 described ; from D it passed through the throttles E into a wide brass tube F, packed 

 with copper gauze, in which it accurately took up the temperature of the surrounding 

 bath before entering the fine metal tubes G, from which it passed through the 

 calorimeter H into the atmosphere. M represents the oil gauge, with which were 

 associated the glass taps T 1 T 2 T 3 , to which further reference will be made. The tank 

 N contained water, which in the experiments at the temperature of the room was 

 siphoned round the jacket of the calorimeter into the vessel W, from which it was 

 poured back again into N. 



VOL. OCX. A. 2 D 



