470 



Canadian Record of Science. 



date, and new experiments of the same sort are in progress. 

 As explained in the previous notice, the object of these 

 experiments is to determine the relative force with which 

 different soluble substances attract water. The process is 

 the reverse of that of evaporation, water vapour being very 

 slowly condensed from a nearly saturated atmosphere by 

 substances soluble in water. Of course, condensation goes 

 on more and more slowly as the solutions become dilute, so 

 that at length, in some cases, years are required for the 

 completion of the experiment. At present we are working 

 with three salts, viz. : sodium, potassium, and lithium chlor- 

 ides. In Series A, sodium and potassium chlorides are 

 put in molecular proportions into small glass tubes, which 

 are enclosed in a stoppered bottle along with a third small 

 tube containing a weighed quantity of water. The propor- 

 tion of water is varied for different experiments. The salts 

 soon deliquesce, the sodium chloride more rapidly than the 

 potassium chloride, and when the proportion of water is 

 small, the water-tube soon becomes dry. It will be interest- 

 ing to trace the progress of a few experiments of this series. 

 Experiment I., sodium chloride, 1.16*72 grm. ; potassium 

 chloride, 1.4882 grm. ; water, 1.44 grm. After 56 days, the 

 sodium chloride has gained 0.8058 grm. of water, the potas- 

 sium chloride 0.6292 grm. and the water-tube is dry. After 

 159 days the sodium chloride is found to have increased its 

 quantity of water at the expense of the potassium chloride, 

 and this process continues, until at the end of 314 days the 

 potassium chloride is very nearly dry. A glance at the 

 following statement will show the progress of invaporation 

 in this case : — 





..1.1672g 

 .1.4882g 





Is 



ft 











5 



ft 





Sodium Chloride. 

 Potassium " 



56 



0.8058 

 0.6292 



159 



1.1978 

 0.2332 



172 



1.2392 

 0.1900 



314 



1.4207 

 0.0072 



410 



1.4183 

 0.0076 



This experiment illustrates the decrease in the rate of in- 

 vaporation as the solution becomes diluter. 



