SALTS OF COPPER. 49 



remains constant, and hence deserves careful consideration. Jones and 

 Uhler found that they could not use solutions of copper bromide in acetone, 

 on account of the chemical action which takes place when the two sub- 

 stances are brought together. It is barely possible that some slight chem- 

 ical change was taking place in these solutions of copper chloride in ace- 

 tone, which might not have been sufficient to produce any precipitation, 

 and which might yet have increased with dilution in such a way as to 

 produce the effect observed in the absorption spectrum. The only other 

 case found in this work where this kind of a deviation from Beer's law 

 was observed was that of ferric chloride in acetone, and here the chemical 

 action was very noticeable indeed, the color of the solution deepening 

 very markedly in the course of a few hours. There is hence a reasonable 

 doubt that the effect here observed is real, and until this is decided it is 

 better not to draw any conclusions from the spectrogram just considered. 



COPPER CHLORIDE IN METHYL ALCOHOL WITH WATER. (See Plate 35.) 



The concentration of the copper salt was constant throughout; and 

 equal to 0.15 normal. The percentages of water in the solutions, beginning 

 with the one whose spectrum is adjacent to the numbered scale, were 0, 4, 8, 

 12 ; 16, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, and 40. The common depth of ab- 

 sorbing layer was 2.0 cm. The exposures to the light of the Nernst lamp and 

 spark lasted 1 and 3 minutes, respectively, the width of the slit being 0.01 cm. 



In the first solution transmission in the blue ceases at A 4500. From 

 this the limit of transmission moves towards the shorter wave-lengths, 

 fairly regularly with increase in the percentage of water in the solution. 

 It will be noticed that the increments in the percentages of water were 

 4 per cent from the first to the sixth solutions, whence they were 2 per cent 

 to the end of the series. The absorption in the region of short wave-lengths 

 also recedes more rapidly from the first to the sixth strips, then more 

 slowly, but with perfect regularity, until the last strip is reached, where 

 the limit of transmission is A 3750. The line formed by the edge of the 

 absorption band in the first six strips is curved somewhat, the concave 

 side facing the region of short wave-lengths. This is what we have always 

 found with the more concentrated solutions of copper chloride. From the 

 sixth to the sixteenth strips the line is nearly straight, the curvature, if 

 any, being in the opposite direction to what it is for the first six strips. 

 In the red the absorption band behaves in an unusual manner, as may 

 be seen from the plate, but which is more easily made out from the nega- 

 tives, of which the following is a description. 



The strip corresponding to the solution containing no water shows 

 complete absorption of all wave-lengths longer than A 6500. The absorp- 

 tion is very w r eak at A 6100, and quite weak even at A 6300, the absorption 

 band accordingly showing a fairly well-defined edge in the neighbor- 

 hood of A 6400. With addition of water up to 12 per cent the absorption 

 increases markedly, the limit of transmission for the fourth strip still 

 being at A 6500, but the shading has increased very much, the absorption 

 being now as great at A 6100 as it was at A 6300 in the first solution. Some 

 absorption is evident as far down as A 6000. From the fourth to the six- 

 4 



