COPPER CHLORIDE AND CALCIUM CHLORIDE. 



215 



The freezing-point lowerings of the last three solutions of the series could 

 not be determined, since the salts separated out when the attempt was made 

 to freeze the solutions. 



The electrical conductivities, together with the corresponding concentra- 

 tions of some of the solutions containing copper chloride and calcium chloride, 

 are given in table 110. The conductivity data are expressed in reciprocal 

 ohms and reciprocal centimeters. 



TABLE 110. 



The data in the above table are plotted in fig. 75. The abscissae and 

 ordinates denote, respectively, concentration and conductivity. This curve 

 has a well-defined maximum, just like all the preceding curves. 



A peculiar difficulty presented itself when an attempt was made to deter- 

 mine the ohmic resistance of certain of the solutions containing copper chlo- 

 ride, and either calcium chloride or aluminium chloride. The resistance 

 (aside from the cell constant) was first large and then decreased to a defi- 

 nite fixed value. For illustration, the successive resistances of the second 

 solution recorded in the above table were 719.6, 706.9, 703.9, 704.3, 703.8. 

 In all cases the mean of three or more determinations, made after the solu- 

 tion seemed to have reached a steady state, was taken as representing the 

 true ohmic resistance of the solution under investigation. That this phenom- 

 enon could not be ascribed to changes in temperature, or to air-bubbles, or to 

 absorption by the electrode, or to variable resistance and contact in the 

 electrical circuit, was shown by repeated and careful tests of all of these 

 matters, as well as of such other causes for the trouble as were thought of 

 from time to time. It was not consistent with the investigation as a whole 

 to pursue this question further. 



COPPER CHLORIDE AND CALCIUM BROMIDE. [See plates 14 (a), 14 (6), 15 (a), 



15(6), 16(o), and 16 (fe).] 



The concentration of the copper chloride in all of the solutions was the 

 constant 0.398. The concentrations of the calcium bromide were 0.000, 

 0.254, 0.508, 0.763, 1.017, 1.271, 1.525, 2.033, 2.542, 3.050, 3.389, 3.804. 

 Each of the first six increments of concentration equals 0.2542; and each of 

 the next three equals 0.5084. The one next to the last has the value 0.339, 



