COPPER CHLORIDE AND CALCIUM CHLORIDE. 213 



COPPER CHLORIDE AND CALCIUM CHLORIDE. [See plate 13.] 



The concentration of the copper chloride in all of the solutions had a 

 constant value 0.398. The concentrations of the calcium chloride were 0.000, 

 0.271, 0.541, 0.812, 1.082, 1.353, 1.624, 1.894, 2.165, 2.435, 2.706, 2.977, 

 3.247, 3.518, 3.788, 4.041. All the increments of concentration have the 

 value 0.2706, except the last one, and its value is 0.253. The concentration 

 of the mother-solution of calcium chloride was 4.51. The colors of the solu- 

 tions commenced with clear blue for the most dilute solutions, and passed 

 through the various shades of greenish-blue, bluish-green, clear green, and 

 yellowish-green, and the concentration of the calcium chloride increased until 

 a deep greenish-yellow color was reached. 



The photographic strip adjacent to the numbered scale corresponds to 

 the solution that did not contain any of the calcium salt. The second 

 strip corresponds to the solution of concentration 0.271, and so on, until 

 finally the strip next to the comparison spectrum pertains to the most con- 

 centrated solution in the series. The depth of the cell was 1.41 cm. 



The spark line of shortest wave-length recorded by the negative for the 

 most dilute solution was 3436.9 A.V., but the continuous background barely 

 extended to 0.347^. For the solution of concentration 4.041 transmission 

 is shown by the negative, and began at 0.506/<. Since the successive differ- 

 ences in concentration of the first fifteen solutions are all equal, the spectro- 

 gram shows at a glance the dependence of the limit of absorption of the 

 region which included the ultra-violet upon the concentration of the dehy- 

 drating agent. That the locus of the left-hand ends of the photographic 

 strips is, as would be expected, not a straight line, but a decided smooth 

 curve, is very apparent. In fact, the band increased in width at the only 

 measurable end by approximately 160 A. U. as the concentration changed 

 from 0.271 to 0.541; but this limit of absorption only moved by about 65 

 A. U. as the concentration passed from 3.518 to 3.788. In other words, 

 the less refrangible end of the ultra-violet band seems to tend towards a defi- 

 nite limit as the concentration of the calcium chloride increased. That this 

 absorption is primarily due to the copper chloride, and not to the ultra-violet 

 band of the calcium salt as such, follows at once from a consideration of 

 plates 3 (6), 5, and 11 (a), and the remarks on the corresponding pages. The 

 change in color of the solutions from blue to green, with increasing amount 

 of calcium chloride, simply means that the ultra-violet band, which did not 

 encroach upon the visible spectrum in the case of the blue solutions, had 

 advanced into the visible spectrum and absorbed the violet and blue to a 

 greater or less extent in the case of the green and greenish-yellow solutions. 



Eye observations of the solutions were made with the aid of the cell having 

 two compartments. The data thus obtained for the shorter wave-lengths 



