PEA ING a Vie oon 
Sodium oxalate, 3% sol. 100 ccm 700 min. 
Glycerine 3.ccm 21 min. 
Potassium chlorate 0.5 g oo 20: 
Heat the sodium oxalate solution to 40° to 50° C. (104° to 
122° F.), add the iron salt, the chlorate, and the glycerine; 
pour on to the gum, rub until dissolved, and strain through 
linen. The chlorate can with advantage be replaced by about 
10 to 20 drops of 1 per cent solution of potassium chromate. 
C. Mercuric chloride, 5% sol. 20ccm 140 min. 
Sodium oxalate, 3% sol. 40 ccm 280 min. 
Gum arabic 20 ccm 140 min. 
Glycerine 1.8 ccm 12.5 min. 
This is prepared in the same way as B. For sensitising 
2000 qcm (310 sq. in.) use: 
Solution A 5 ccm 35 min. 
Solution B 4 ccm 28 min. 
Solution C 4 ccm 28 min. 
The following may also be used ( Watzek) : 
Sodium ferric oxalate 10 ccm 160 min. 
Potassium chloroplatinite 6 ccm 92 min. 
Mercuric chloride 5 drops 5 drops 
Add a few drops of 1 per cent solution of potassium bichro- 
mate to obtain contrasts. The other salts should be saturated 
solutions at 18° C. (64° F.). The paper should be sized 
with starch or arrowroot, two to three coats being used. 
Printing is continued until the desired depth is reached. 
RESTORING PLATINOTYPES.—Sometimes through insuff- 
cient washing the paper of platinotypes yellows with age, due 
to the action of the air on the residue of iron salts. This 
stain can be removed by treatment with a weak solution of 
chloride of lime or eau de Javelle. Make a saturated solu- 
tion of chloride of lime in water, filter, and add 1 part of the 
clear solution to 100 parts of water, then add dilute hydro- 
