71 
1908-9.] A Question in Absorption Spectroscopy. 
The molecular extinction coefficients of the five salts were found to he 
as follows : — 
CuS0 4 
*5H 2 0. 
CoC1 2 *6H 2 0. 
NiS0 4 
•7H 2 0. 
K 2 Cr 2 0 7 . 
U0 2 (N0 3 ) 2 -6H 2 0. 
A 
A 
a 
A 
A 
A 
A 
A 
A 
A 
598 
•883 
633 
*514 
693 
2-112 
697 
•14 
630 
•035 
590 
•672 
620 
•518 
660 
1-951 
633 
•46 
567 
•039 
572 
•399 
598 
•527 
630 
1-493 
588 
•68 
521 
•044 
537 
•122 
591 
•552 
617 
1-092 
568 
1-10 
498 
•0605 
450 
•026 
584 
•620 
596 
•672 
552 
2-11 
491 
•181 
576 
•738 
586 
•445 
544 
3-69 
488 
•404 
568 
•970 
567 
•259 
537 
7-06 
485 
•413 
552 
1*817 
550 
•185 
529 
12-75 
483 
•355 
537 
3-120 
535 
•158 
521 
23-47 
480 
•361 
522 
4*561 
521 
•114 
510 
65-69 
475 
•421 
515 
4-827 
509 
•097 
499 
119-3 
470 
•902 
510 
5-238 
498 
•085 
489 
179-1 
466 
•941 
504 
5-509 
488 
•104 
480 
251-9 
455 
1-445 
499 
5*172 
479 
•186 
471 
322-6 
470 
•293 
463 
394-4 
462 
•381 
448 
•562 
In the case of uranyl nitrate with cobalt chloride and potassium dichro- 
mate and in the case of cobalt chloride with copper sulphate, potassium 
dichromate, and nickel sulphate, no change could be detected as a result of 
mixing. Different strengths were used, and about seven points in the 
spectrum were examined. An alteration of of the intensity transmitted 
could have been detected in the most favourable cases. 
It was different in the case of uranyl nitrate with copper sulphate and 
nickel sulphate. The spectrum of uranyl nitrate consists of bands in the 
violet, the first two of which at 486 and 473 are very easily seen with the 
eye although the table of molecular extinction coefficients does not show 
the second well. On mixing, in each of the above cases, both these bands 
were displaced towards the red. The shift varied with the strengths of 
the solutions used ; it seemed to be proportional to the quantity of sulphate 
present divided by the quantity of nitrate. As the first two bands of 
uranyl sulphate are at 491 and 477, as no shift was produced by mixing 
copper nitrate and uranyl nitrate and as the same shift was produced by 
adding sulphuric acid to uranyl nitrate, there seems no doubt that the shift 
is chemical. 
We next repeated Melde’s work with carmine. This was done only 
spectroscopically. A solution of carmine in ammonia which has bands at 
