Section III., 188-4. [ 69 ] Trans. Roy. Soo. Canada. 



II. — On the Density and Thermal Expansion of Solutions of Copper Sulphate. 

 By J. a. MAcaREGOK, M.A., D.Sc, F.R.S.E. 



(Read May, 1884.) 



The experiments described in this paper were undertaken with the object of providing 

 data for the correction of direct measurements, made by Professor Ewiug and the author, of 

 the change of bulk produced in water by the addition of small quantities of anhydrous copper 

 sulphate. We had found by measurements of the density ' of solutions formed by adding 

 the crystallized salt to water, that the volume of certain solutions of this salt was less than 

 the volume of the water which the solution contained. It followed that if the result of the 

 solution of auhydro\is salt was the same as that of the solution of crystallized salt (the 

 respective solutions formed having the same constitution), the addition of anhydrous salt to 

 water in certain proportions must produce contraction. This we found to be the case, and 

 we were able to make, roughly, direct measïirements of the amount of the contraction. ' 

 Accurate measurements rec^uired a knowledge of the expansion of weak solutions of differ- 

 ent strengths with temperature, and this expansion it was my object to determine. Having 

 made the desired observations with weak solutions, it seemed worth while to continue the 

 investigation with stronger solutions as well. 



The expansion of the solutions was studied by measuring their density at different 

 temperatures. The density was measured by means of a specific-gravity bottle of the ordi- 

 nary form. It was made of thin glass, but the glass was not so thin as to have its volume 

 appreciably changed by any pressure to which its walls were subjected. It was provided 

 with a carefiilly ground stopper having a capillary perforation. The balance used was one 

 of Oertliug's, capable of indicating a difference of a tenth of a milligramme. The rough 

 measurements of density were of course corrected, so as to eliminate the errors due to the 

 expansion of water and of the bottle, and to the displacement of air. Special measurements 

 were made to determine the expansion of the bottle. For the expansion of water I used 

 Volkmann's ' table, obtained by a combination of the experimental results of Hao-en, 

 Matthiessen, Pierre, Kop]5 and Jolly. The densities given below are all expressed in 

 grammes per cubic centimetre, that is, they are specific gravities referred to water at 4° C. 

 as standard. 



The best thermometer at my disposal was one which could shew temperature differ- 

 ences of one-tenth of a degree centigrade. In the numbers by which temperatures are 

 described in the tables given below, the figures in the second place of decimals are the 

 result of corrections. The errors of the fixed points of the thermometer used were 



' Trans. Roy. Soe. Edin., vol. xxvii (1873), p. 51. 



^Report of British Association, 1877 ; Nature, vol. xvi (1877), p. 37G. 



nVied. Ann. Phys. Chom., Bd. xiv (1881), p. 277. 



