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IX. 
ON THE CONDITIONS OF EQUILIBRIUM OF DELIQUESCENT AND HYGRO- 
SCOPIC SALTS OF COPPER, COBALT, AND NICKEL, WITH RESPECT 
TO ATMOSPHERIC MOISTURE. By W. N. HARTLEY, F.R.S., Honorary 
Fellow of King’s College, London ; Professor of Chemistry, Royal College of Science, 
Dublin. (Piatrs XXIII., XXIV., anp XXYV.) 
[Read Marcu 20, 1901.} 
In two published papers I have described some remarkable changes in colour 
which are seen on dissolving pure and neutral crystallized salts in water, and on 
dilution of their saturated solutions with water.* The behaviour of cupric 
bromide was described ; and the conclusion was drawn that both the chloride and 
bromide, with two and five molecules of water, respectively undergo partial de- 
hydration when concentrated solutions are prepared at 60° F. 
These conclusions appear to have been justified and confirmed by the 
following experiments, which were made with the object of ascertaining the 
conditions of equilibrium under ordinary atmospheric changes which govern 
the formation of hydrates of the hygroscopic and deliquescent haloid salts of 
copper, cobalt, and nickel. 
Mernop or EXPERIMENTING. 
A large bell-jar was placed on three blocks of wood an inch in thickness, and 
within the jar were six beakers, one of which contained distilled water. The 
other five were each weighed empty, and weighed again after adding a small 
quantity of one of the salts to be examined. Inside the jar dry and wet bulb 
thermometers were placed to determine the tension of aqueous vapour, and 
outside was a Six’S maximum and minimum thermometer. 
Every day, at as nearly as could be the same hour, the thermometer readings 
were recorded in the following manner :— 
Time. 1899. Dry bulb. Wet bulb. Max. Min. At instant. Mean. 
10 a.m. Deer. 15th. 47°°5, 45°°5. 55°-5. 40°°25. 48°°0. 47°°9, 
The pressure of aqueous vapour was found from the difference between the 
wet and dry bulb thermometers by reference to Glaisher’s hygrometic tables. 
* Journ. Chem. Soc. of London, vol. xxviil., 1875, p. 206; Sci. Trans. Roy. Dublin Soe., vol. vii., 
ser. 11, 1900, pp. 2538-312. 
TRANS. ROY. DUB. SOC., N.S. VOL, VII., PART IX, 9X 
