SALTS OF COPPER. 47 



spending depths of absorbing layer were 6, 7.5, 9.5, 12, 15, 19, and 24 mm. 

 For B the concentrations were 0.233, 0.186, 0.147, 0.116, 0.093, 0.073, and 

 0.058; the depths of absorbing layer were the same as in set A. 



The solutions were all green, the intensity of the color only chang- 

 ing with dilution. Exposures to the light of the Nernst lamp and spark 

 lasted for 1 and 3 minutes, respectively, the slit having the usual width 

 of 0.01 cm. 



As in the aqueous solutions we have two regions of absorption, one in 

 the blue, violet, and ultra-violet, the other in the red. Both regions con- 

 tract somewhat on decreasing the concentration of the solutions, but the 

 one in the violet region contracts much more than the one in the red. 



The limit of transmission for the first strip in A is at A 4800, while for 

 the seventh strip it is at A 4630. The edge of the band forms a line which 

 is slightly curved at first, the concave side being towards the violet. From 

 the third to the seventh strips the edge forms a line which is sensibly 

 straight. In B the limit of transmission for the first strip is A 4420, while 

 for the seventh it is A 4200, the edge forming a line which is very nearly 

 straight. From the fourth to the seventh a slight curvature may be noted, 

 the convex side turning towards the violet. On the whole this band be- 

 haves exactly like it does in aqueous solution, the only difference being 

 the greater deviation from Beer's law in that case. 



In the red, the first strip in A shows transmission to X 6500, with shad- 

 ing from A 6050; the seventh strip, transmission to X 6580, shading from 

 A 6100. The first strip in B shows transmission to A 6950, shading percep- 

 tibly from A 6550; while the seventh strip shows transmission as far as 

 A 7020, with shading from A 6600. In both sets, therefore, the band narrows 

 slightly with dilution, and in B quite uniformly with the decrease of con- 

 centration. In A, however, the narrowing is considerably more rapid at 

 first. Here, again, we find that the band behaves in a manner very similar 

 to what we found in the aqueous solution, only the change is somewhat 

 slower. The decrease in concentration from strip to strip, here, is, however, 

 only about half what it was in the aqueous solution; and taking this into 

 consideration the difference is not as great as it seems at first glance. 



COPPER CHLORIDE IN ETHYL ALCOHOL BEER'S LAW. (See Plate 33.) 



The concentrations of the solutions used in making the negative for 

 A, beginning with the one whose spectrum is adjacent to the numbered 

 scale, were 0.744, 0.595, 0.469, 0.372, 0.297, 0.233, and 0.186; the depths 

 of absorbing layer were 6, 7.5, 9.5, 12, 15, 19, and 24 mm. For set B the 

 concentrations were 0.233, 0.186, 0.147, 0.116, 0.093, 0.073, and 0.058; 

 the depths of cell were the same as for set A. 



All the solutions were green as seen in their bottles, the color being 

 somewhat more intense than was the case with the methyl alcohol solutions. 



The exposures were made only to the Nernst lamp, since it was shown 

 that all the solutions were opaque beyond the visible spectrum. The 

 exposure lasted for 1 J minutes, the width of the slit being as usual 0.01 cm. 



We have the same bands as in the methyl alcohol solutions, with the 

 difference that here they are somewhat wider. 



