164 On Steam and Brines 



As above described, each experiment must be expected to 

 take from an hour and a half to two hjpurs. 



Steam Condensed in Heating the Apparatus. When the 

 thermometer is in its usual experimental position, that 

 is, with its bulb in the middle of the salt and so low down 

 that it will be immersed in the brine or water whenever 

 enough steam has condensed to make this possible, and 

 the whole of the working part of the stem is in the steam 

 space, it arrives at the maximum temperature almost simul- 

 taneously with the first exit of steam from the apparatus ; 

 but that part of the steam tube situated above the exit tube 

 is not yet thoroughly warmed through, and a little time must 

 be allowed during which the strength of the steam current 

 increases until it becomes steady. In ordinary circumstances 

 the apparatus cannot be held to be warmed through in less 

 than 90 seconds, and, for purposes of heat calculation, 

 we take the initial period of heating to be two minutes, 

 during which it may be said always to be complete. Experi- 

 ments made with boiling mixture tube, weighing with ther- 

 mometer 239-65 grms., showed the following results : 



Steam condensed ... grrns. 8'3 8'3 8'5 8'35 

 In time ... ... ... seconds 85 90 100 90 



From these we find the mean amount of steam condensed 

 in the first 90 seconds 8'25 grms. When the steam was passed 

 through for exactly two minutes before weighing, the following 

 weights of steam were condensed : 9*1, 8'9, and 9-0 grms., or 

 a mean of 9 - o grms. 



For vessels of the same pattern and nearly the same size 

 the quantity of steam required to heat them or to keep them 

 hot depends simply on the amount of glass. 



Thus, our apparatus weighs 239'65 grms., and may be 

 considered to be all glass. If the specific heat of the glass 

 be O'2, then the amount of water thermally equivalent to it 

 is 48 grms. In order to raise the temperature of 48 grms. 

 water from 15 C. to 100 C, we require 4080 g. C. (gramme- 

 degrees-Celsius), and this can be supplied by 7-61 grms. steam 

 saturated at ioo c C., and condensing at 100 C. But the 



