STEAM AND BRINES. 539 



calculate the amount of steam required to warm another apparatus of the same type on 

 the basis of its weight. 



In order to determine more carefully the amount of steam required to keep the 

 apparatus at a temperature of 100° C. during some time, two experiments were made, 

 the apparatus being dry and cold to begin with. In the first, steam was passed through 

 for 12 minutes, when 22 - 2 grms. were condensed ; in the second, the steam was passed 

 for 32 minutes, when 50*8 grms. were condensed. Allowing that in each case 9 grms. 

 of steam were condensed in the first two minutes, we have 13*2 grms. condensed in 10 

 minutes, and 41 # 8 grms. in 30 minutes. The first is at the rate of 1*32 grms. per 

 minute, and the second at the rate of 1*39 grms. per minute, or a mean of 1'35 grms. 

 per minute. 



Experiments of a similar kind were made with \ NaCl, or 117 grms. of this salt in 

 the tube to begin with. Two minutes were sufficient for heating up to 100° C. In two 

 experiments the amounts of steam condensed were 9*8 and 9*6 respectively, giving a 

 mean of 9 '7 grms. In a similar experiment, where the passage of steam was not 

 stopped until the salt was all dissolved, which took 163- minutes, the steam condensed was 

 31*5 grms. Deducting 97 grms. we have 21*8 grms. condensed in 14^- minutes, or 1*5 

 grms. per minute. The rate of condensation is naturally higher, because salt is being dis- 

 solved. With the apparatus empty at the start, 9*0 grms. steam are condensed in the 

 first two minutes; with a charge of 117 grms. chloride of sodium, 97 grms. of steam 

 are required; the excess, or 07 grm., may be taken as the steam condensed by the 

 NaCl in the two minutes, and as constant for the same amount of NaCl in other 

 apparatus. 



The boiling tube used in all the experiments up to 26th October 1897 weighed, 

 with thermometer, 157*3 grms. This would require 5*5 grms. of steam in order to raise 

 it to 100° C, and the heating would be complete in one minute instead of in one and a half 

 minutes as with the apparatus weighing 239 grms. Allowing 1*0 grm. for the amount 

 of steam condensed in the next minute, we should have, after two minutes, 6*5 grms. steam 

 condensed. Where A NaCl was used, we should have to add 07, and the amount thus 

 condensed at the end of the first two minutes would be 7*2 grms. The rate of con- 

 densation per minute, after the first two minutes, would be § 1*35 or 0'9 grm., and 

 adding 0'15 for the chloride of sodium, we have 1'05 grms. per minute, taking 30*4 

 grms. as the amount of steam required to be condensed for -^ NaCl. 



Localities where Experiments ivere Made. — The lowest station, and the one 

 representing the sea level, was my laboratory in Edinburgh : its elevation is about 

 85 metres, or 279 feet, above the sea. Although a large number of experiments 

 in this field had been made in the course of previous years, those utilised for this paper 

 were all made after my return from Switzerland, with the same apparatus and the 

 same thermometers that were used there, and with the experiments arranged on the 

 same plan. Being the last series, it is also the most symmetrical. 



