SULPHIDE, TONING 247 
GENERAL Notes oN SuLPHUR ToninGc.—R. Bullock of 
the Kodak Research Laboratory, finds that the character of 
the emulsion has considerable influence on the resulting 
colour; the faster the emulsion the more purple the colour, 
while slow papers tend to give yellowish tones. Also, with a 
given paper, the degree of development exerts some action, 
although this may be masked by the character of the emulsion. 
With a given paper and method of making the black and 
white print, the hypo-alum and liver of sulphur (potassa 
sulphurata) toning processes give practically identical results, 
while the indirect methods, that is, those in which the image 
is bleached first, tend to give yellowish prints. The effect of 
a preliminary treatment of the black and white print with 
sulphide, prior to bleaching, is to give mixed direct and 
indirect sulphide toning; the results depending on the exact 
procedure followed, and, therefore, varying in colour. In 
the indirect process there is no advantage in increasing the 
ratio of the bromide to more than one-third of the ferri- 
cyanide. With 10 per cent of ferricyanide, the colour is more 
yellowish and the bleaching very rapid; with from 3 to 1 per 
cent, the bleaching is practically no longer and the colours 
normal: with much less than 1 per cent, bleaching is much 
slower but the colour just as good. The most advisable 
strength would thus appear to be 3 per cent, or 30¢ ferri- 
cyanide per liter (230 gr. to 160z.) with 10g (77 gr.) am- 
monium bromide respectively. No advantage is to be found 
by the use of chlorides, while with iodides the tones are more 
yellowish. For the sulphide bath, a strength of 3 per cent 
is the best, and the bath should be unsparingly used so as not 
to exhaust it. Dipping the prints for about 10 seconds into 
a 1 per cent solution of sodium carbonate, immediately before 
the sulphide bath, tends to give more purplish tones, particu- 
larly with development papers, and when a chloride bleach is 
