COLOUR PHOTOGRAPHY 345 
The green filter is always difficult to adjust, and it is advis- 
able to make four or five of different depths, increasing the 
quantity of dye by one-fifth each time. 
Red filter : 
Tartrazine 2.03 g 20.17 gr. 
Rose Bengal 772; 7 NSZ ot, 
In order to prevent the double reflection from the back of the 
plain mirrors in the chromoscope, under the red filter should 
be placed a plain glass coated on the back with: 
Patent blue 0.0285 g 0.284 gr. 
Under the blue filter, should be placed a plain mirror coated 
with: 
) @artrazine 0.0142 g 0.142 er. 
Naphthol green 0.023 ¢ O227 ier 
Patent blue 0.0345 g 0.340 er. 
AUTOCHROME PLATES.—Primary developer: 
A. Pyrogallol 30 g 230 gr. 
Potassium bromide 30g 230 gr. 
Sodium bisulphite lye 2 drops 1 drop 
Water to 1000 ccm 16 oz. 
B. Sodium sulphite, dry 100 g Th hs 
Ammonia, sp. gr. 0.92 150 ccm 2 oz., 252 min. 
Water to 1000 ccm 16 oz. 
For use this stock solution should be diluted with 3 times its 
volume of water. The actual developer is: 
Solution A 100 parts 
Solution B, diluted 100 parts 
Water to 1000 parts 
To compensate for errors in exposure and variations in 
temperature, the following system was devised: Have ready 
in a small measure 45 ccm (345 min.) of dilute B solution 
to be added wholly or partly to the bath during development. 
if necessary. As soon as the plate is in the developer, count 
