SALTS OF NICKEL. 43 



one-fourth as long as that for the spark spectrum in the strips, the former 

 has about the same intensity as the latter. Also the extreme ultra-violet 

 lines shown by the comparison strip do not appear in the spark spec- 

 trum transmitted through the solutions; which indicates the presence of 

 a band in the region below A 2350. 



The A 3960 band has exactly the same width in all the strips, corre- 

 sponding to the solutions of either A or B, showing that Beer's law holds 

 exactly. The limits of transmission in A are A 3600 and A 4320, and in B 

 A 3700 and A 4250, which gives the center of the band in A at A 3960 and 

 in B at A 3975. 



In the red A shows complete absorption beyond A 6400, and very 

 strong shading from A 6400 to A 5900. Indications are that the absorption 

 in this region decreases very slightly with dilution. B shows faint trans- 

 mission to A 7400, with rather strong shading from A 6100. No appre- 

 ciable change in the absorption with dilution can be noted from the spec- 

 trogram. A comparison of the seventh strip of B with the seventh strip 

 of A, Plate 25, shows that the width of the A 3960 band, as shown by the 

 two, is almost exactly the same. The depth of cell in both cases was 24 

 mm., but the concentration of the chloride solution was 0.33, while that 

 of the sulphate was only 0.20. This indicates a greater absorbing power 

 for the sulphate in this region of the spectrum. A comparison of the 

 red ends of the same strips shows that the sulphate solution absorbs the 

 red much more intensely than the chloride. 



NICKEL ACETATE IN WATER BEER'S LAW. (See Plate 29.) 



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 0.50, 0.40, 0.31, 0.25, 0.20, 0.15, and 0.13; the corresponding 

 depths of cell were 6, 7.5, 9.5, 12, 15, 19, and 24 mm. For B the con- 

 centrations were 0.20, 0.16, 0.13, 0.10, 0.08, 0.06, and 0.05; the depths of 

 cell were the same as in A. The exposures to the Nernst lamp and spark 

 lasted for 1 and 2 minutes, respectively, the slit having a width of 0.01 cm. 



There is evidence of a band in the extreme ultra-violet, the limit of 

 transmission in A being A 2400. The general absorption in the region 

 between this and the A 3960 band is not very strong, clue to the compara- 

 tively small concentration of the solutions used. 



The A 3960 band narrows somewhat with dilution in A, the fifth, sixth, 

 and seventh strips showing slight transmission even at its center. In B 

 the band has become faint, though still showing distinctly. It remains 

 of sensibly the same intensity with dilution. In the red A shows some 

 transmission as far as A 7400, with shading from about A 6600. In B 

 the red absorption was too faint and diffuse to be registered on the 

 photographic plate. 



A comparison of the seventh strip of A with the seventh strip of Plate 

 26 B shows that although the absorption of the acetate is somewhat 

 greater it is not very much so. The depth of absorbing layer used in mak- 

 ing the two strips was the same, namely 24 mm., but the concentration of 

 the chloride was 0.16 while that of the acetate was only 0.13. Hence, the 



