200 



HYDRATES IN AQUEOUS SOLUTION. 



fiftieth normal aqueous solution of potassium chloride at 25, the conduc- 

 tivity in reciprocal Siemens units is 129.7; therefore, the conductivity in 

 reciprocal ohms and reciprocal centimeters equals 



129.7 X 1.063 

 1,000 X 50 = - 02757 = A " 



Since for a given cell, at a given temperature, the ratio of the specific 

 conductivities of any two solutions is by definition equal to the inverse ratio 

 of the ohmic resistance, it is only necessary to determine successively the 

 resistance in the same cell and at constant temperature of a standard solu- 

 tion and of a solution to be tested, and then to multiply the specific conduc- 

 tivity of the standard solution by the ratio of the ohmic resistance of the 

 standard solution to the ohmic resistance of the solution under investigation, 

 in order to find the value of the specific conductivity of the solution in ques- 

 tion. In obvious notation 



TABLE 103. 



Figure 72 shows graphically the functional relation between the electrical 

 conductivity and the concentration of the solutions under consideration. 

 The abscissae denote the concentrations of the calcium chloride, and the 

 ordinates give the corresponding conductivities in the units specified above. 

 The concentration of the cobalt chloride was constant =0.271. It is inter- 

 esting to notice that the conductivity rose to a maximum value, and then 

 decreased as the quantity of the dehydrating agent in the solutions increased. 



COBALT CHLORIDE AND CALCIUM BROMIDE. [See plate 10.] 



The cobalt chloride had the concentration 0.271 in all of the solutions 

 of the set now under consideration. The concentrations of the calcium 

 bromide were 0.000, 0.189, 0.379, 0.568, 0.757, 0.947, 1.136, 1.515, 1.893, 



