240 PHOTOGRAPHIC FACTS AND FORMULAS 
print and cause blisters. A stock solution that will keep 
(Blake-Smith) can be made as follows: 
Sodium sulphide 330 g 5 oz. 
Sodium sulphite, dry 50to65¢gr. %toloz. 
Water 1000 ccm 15 oz. 
For use dilute with 9 volumes of water. The bath should 
not be used too long. 
Ammonium or barium sulphide may be used instead of 
the sodium compound: 
Ammonium sulphide 10to20ccm 77 to 154 min. 
Water 1000 ccm 16 oz. 
Or: 
Barium sulphide 552 25 gr. 
Water 1000 ccm 16/02; 
Shake the latter solution for a few minutes and allow to 
stand for any precipitate to settle, and then filter. The 
barium salt is more stable than the sodium and therefore 
preferable in practice. 
For chlorising or bromising the image, quinone has been 
recommended (Lumiére & Seyewetz) : 
Quinone 5g 38%4 gr. 
Sodium chloride (salt) 6g 46 gr. 
Sulphuric acid 3.ccm 23 min. 
Water 1000 ccm 16 oz. 
Potassium bromide 11 g (85 gr.) may be used instead of the 
sodium chloride. The bleached images are amenable to 
exactly the same treatment as all other bleached images. 
Molybdenum and tin sulphur compounds, called sulpho- or 
thiomolybdates and stannates have been proposed (Smith) ; 
the former was introduced commercially as ‘“(Cubrome” and 
gives excellent results. This solution can be made as fol- 
lows: 
Ammonium molybdate 100 g 770 gr. 
