Colour and Chemical Constitution. 
311 
green to Doebner's violet, 619 ~- 561, showing that the colour-factor for four 
methyl-groups applies also in the thiophenazine series of dyes. 
Addendum, 15/9/20. — Since the diphenylcarbinol dyes can be calculated 
from the triphenylcarbinol series by dividing by 1 026, we can next calculate 
the indamine dyes by finding a factor for the substitution of — N = for 
— CH = in the centre. This factor is about 1*20. Thus to calculate 
Bindschedler's green from malachite -green, first divide by 1*026, giving 
Michler's hydrol, then multiply by 1*20, giving tetramethylindamine : next 
from the indamines the oxazines and thiazines can be calculated. The factor 
is similar for both, about 0*90 for the oxo-linkage (also occurring in fluores- 
cein) and 0*92 for — S — linkage in methylene -blue. Metliylene-blue cal- 
culated from malachite-green is 619 1*026 x 1*20 x '92 = 665. 
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