Colour and Chemical Constitution. 
73 
I hope that some one will examine the thioxanthhydrol dyes, and thus 
enable the thio-f actor also to be stated to three places of decimals. 
(3) The imino-linhage. — The acridine dyes are NH-derivatives of the 
benzhydrol dyes : similarly the phenazines are related to the indophenols. 
('0 Flavine (diaminoacridine) has A about 427, whilst diaminobenzhydrol 
has A 548. The NH ratio is here 0 780. 
(b) Benzoflavine A (substance No. 27 without the methyl-groups) has 
A about 450 (broad). The corresponding substance without the NH group 
is Doebner's violet, which has A 562. The NH ratio is here 0*80. This, 
being exceptional, is probably wrong. The acridine dyes analogous to 
thephthaleins and rhodamines appear to be little known, and are inaccessible 
here (' Beilstein,' iv, supplement, p. 879. Calculated A 438.) 
(c) Bisdimethylamino-phenazine has A about 565, and Bindschedler's 
green A 730. The NH ratio is here 07 74. 
(d) Dioxyphenazine lias A about 510 (broad), and indophenol A 650. 
The NH ratio is here 0785. 
(e) Safrai line (without methyl groups) has A 525 compared with indamine 
A 660, giving 0796 for the NPh ratio, whence NH is 0796 T026 = 0778. 
(4) The methylene-linlcage. — This is inferred from the acridine dyes, this 
time compared with the indophenols, on the principle that when two linkages 
are present it does not matter which is the oxidised one, i.e. (CH, + NOH) 
= (CHOH + NH). 
(a) Flavine / indamine — 427 / 660. Value of /CH 2 \ = 0'647. 
(b) Dioxyacridine / indophenol = 421 / 650. Value of /CH 2 \ = 0649. 
The oxidised factors. — Here the supposition is made that since a factorial 
scheme has been shown to be generally successful, and since Watson and 
Meek have established the factor f for the change of linkage from CHOH 
to CO, this factor f will also hold for any other oxidation of the linkage. 
Hence the value of /CHOH\ is f of /CH 2 \ = 0 39, and /NOH\ = 
f of 078, and so on. That this supposition is correct is proved by the 
consistency of the results given in this paper. 
The next step is to calculate the colour of the unobservable singly- 
linked dicyclic substances : 
(1) Dioxy -phenyl ether. — This is (1) dioxyxanthhydrol less CHOH: 
calculated A 479 -f- 0-39 = A 1229, (2) resorufine less NOH : calculated A 576 
~ 0 468 = A 1230. 
(2) The calculation for the sulphur-ether dioxyphenyl sulphide gives 
A 1258. 
(3) Dioxy-diphenylamine. — This from dioxyphenazine is calculated to 
have A 510 —■ 0 468 = A 1090 : from dioxyacridine the calculated value is 
A 421 . -T- 0-39 = A 1080 : from resorufin A 576 -f- (f of 0-891) = A 1077 and 
so on. 
(4) Dioxy-diphenylmethane. — This from dioxyacridine is calculated to 
