446 On the Action of various Coloured Bodies on the Spectrum. 



green and approaching to n. A faint band remains at m n. 

 Absorption then takes place at B, and C m or B m is the per- 

 sistent red. 



19. Carbazotic Acid is more intensely yellow than the carba- 

 zotate of potash. It begins to act upon the spectrum at the 

 violet, and then absorbs up to b. 



20. Ammoniuret of Nickel, a fine deep blue by daylight, 

 and pink by candle-light. It attacks the spectrum at D and D 2, 

 absorbing the space between them, the absorption advancing on 

 each side of D, but deepening the whole red space till it nearly 

 disappears, and leaving only the green and the blue with scarcely 

 any of the violet. 



21. Nitrate of Copper, greenish blue by daylight, and bluish 

 green by candle-light. It attacks the red space generally, be- 

 ginning chiefly at the extremity, and advancing to D, then to 

 D 2, leaving the yellowish green more yellow, and also all the blue 

 and almost all the violet. The blue is whiter, and the green 

 space is yellower, indicating that the red has been partially 

 absorbed throughout much of the spectrum. 



A weak solution first absorbs B C or Be sharply, and also 

 widens m. 



22. Nitrate of Nickel, a pale muddy green, but yellowish at 

 considerable thicknesses. It attacks the red space at its extremity, 

 and at the same time the other end of the spectrum up to D 4, 

 leaving the yellowish white band with green on one side and red 

 on the other. It absorbs blue at small thicknesses, leaving 

 violet in place of the blue. 



23. Ammoniuret of Copper, fine deep blue in day- and can- 

 dle-light. It attacks the red and green, generally beginning at 

 the red end, and absorbing up to F, leaving the blue and violet. 



24. Muriate of Copper, pale green. It attacks the red 

 space at its extremity, and absorbs the violet. 



25. Sulphate and Nitrate of Iron, orange-yellow. It attacks the 

 spectrum at the violet end, and advances gradually towards D 4. 



26. Chromate of Potash (not neutral), intense yellow. It be- 

 gins at the violet end, and advances gradually up to b. 



27. Oxalate of Chromium and Potash. I have fully described 

 the properties of this remarkable salt in the Philosophical 

 Transactions, 1835, p. 91. It has a specific action upon a red 

 ray between A and B, its place being such that BX= \ B a. It 

 is a sharp and narrow black band, forming a fixed line in all 

 artificial lights, and of great practical value in measuring refrac- 

 tive powers. 



28. Arsenite of Copper in Muriatic Acid, a fine green. It 

 absorbs the red and violet ends of the spectrum, leaving the red 

 from D to C a palish flesh or salmon-colour. 



