828 PROFESSOR PIAZZI SMYTH ON COLOUR, 
2. BICHROMATE OF POTASH—continued. 


Solution = strength of 3,. 

Intensity. vr Wave-number | Colour Region by 

in Brit. inch. Wave-number. 
Light begins. : : ; ; ; 0 25°29 34 495 | Crimson Rep 
Maximum Licutr e : ‘ 2 , 8 25:96 42 680 | AMBER 
End all .. é : : é , ‘ 0 26:28 45 851 CITRON 


Solution = strength of 74,, or close to saturation. 



Light begins. : : A : 0 25°28 34 364 | Crimson RED 
Maximum Licur : : : < : 6 25°94 42 481 | AMBER 
Endall . : : ‘ ; ‘ 0 26°23 45 331 | Crrron 


This solution better suited than any other yet tried for achromatising simple objectives, one 
colour, its own yellow, excepted. 
New and transparent orange bichromate solution for galvanic battery shows no black lines, 
only one broad band of light from red to yellow and citron. 
Old, dark, greenish-brown bichromate solution, nearly used up in a battery, shows one 
reddish band, placed thus :— 

Wave-number | Colour Region by 
in Brit. inch. | Wave-number. 
25°38 35 714 | Rep 
25°50 37 411 | SCARLET 
25°67 39 417 | ORANGE 

and in this band is a hazy attempt at a dark line in— 

Wave-number | Colour Region by 
in Brit. inch. | Wave-number. 

25°52 37 651 |-ScaRLer 

N.£.—This is not the clear sharp line seen in oxalate of chromium and potash. 
3. GAMBOGE. 
Primrose yellow in solution, but opaque. 
4. TEA. 
Tried in hot solution, gave one band in orange and citron, but dull ; 
and when cold was nearly opaque. 

