STEAM AND BRINES. 537 



removed from the T tube and the operation is interrupted. The receiver is then quickly 

 disconnected from the india-rubber tube, and suspended from the scale, which is within 

 arm's reach from the working bench, and the weight ascertained to the nearest deci- 

 gramme. The receiver is then immediately reconnected with the boiler, the cork 

 inserted, and boiling recommenced. Steam is passed until the temperature has fallen to 

 the first attainable whole number of degrees above the temperature of saturated steam , 

 when it is interrupted, the weight observed and the receiver reconnected, to be again 

 weighed when the next whole degree is reached, and so on until so much water has col- 

 lected in the receiver that the steam can no longer be passed through it at a suitable 

 rate without risk of throwing out some of its contents. The temperature of saturated 

 steam is now again determined with the thermometer used in the experiments. This 

 has been determined several times during the experiment in another apparatus and with 

 another thermometer. This enables the effect of any change in the barometric pressure 

 to be spread correctly over the time occupied by the experiment. This series of obser- 

 vations gives the concentration of solutions whose boiling points are higher than that 

 of pure water by certain definite amounts. The small uncertainty which attaches to 

 the determination of the concentration of the boiling saturated solution does not affect 

 that of the less concentrated solution. "When the saturated solution has been weighed 

 and reconnected with the steam generator, it often happens that, however expeditiously 

 the operation may be performed, some of the salt has crystallised out, and this generally 

 requires an extra amount of heat, or steam condensed, to redissolve it. Then the boiling 

 temperature of the solution when saturated is lowered very much by a small dilution, 

 an effect which diminishes rapidly with increasing dilution. 



As result of the series we have the temperature of the saturated boiling solution 

 and approximately its concentration, also the boiling temperature and exact concentra- 

 tion of a series of more dilute solutions. When the boiling tube has been emptied 

 and washed, steam is blown through it until the whole tube is heated up to the 

 temperature of the steam ; it is then quickly disconnected, the water ejected from it, 

 and air blown through it from the lungs, which in a few seconds dries the inside of the 

 receiver completely. This is the easiest way to dry the inside of all complicated 

 glass apparatus. The glass of the apparatus is always sufficiently massive that when it 

 has been heated to 100° C. it has more than sufficient immediately available heat to 

 evaporate all the water that will adhere to its surface, and still not fall to such a tem- 

 perature as to condense moisture from the air of the lungs. 



The receiver is immediately ready for another experiment. As above de- 

 scribed, each experiment must be expected to take from an hour and a half to two 



hours. 



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, 



VOL. XXXIX. PART III. (NO. 18). 4 M 



