Colour and Chemical Constitution. 279 
Miscellaneous Observations on Azo-dyes and Azomethines. 
i. Ortho-hydroxyazobenzene (alkali) 
^. „ ' „ (acid) 
3. Para- „ ,, 
CHg-der. of (I) = benzeneazo-p-cresol (alkali) 
SOgK- ,, „ = p-phenolsulphonate 
2-4-6-tribromobenzeneazophenol (alkali) 
Benzeneazo-o-bromophenol „ 
2-nitrobenzeneazophenol 
4- 
4-nitrobenzeneazo-ot-naphthol 
Foregoing in alcoholic alkali 
No. 9 in „ . 
4-sulphobenzeneazophenol (alkaii) 
4-bromo- ,, ,, 
4-ethoxy- „ „ ,, 
4-sulphobenzeneazo-o-cresol ,, 
4- „ ,, -m- „ „ 
Benzeneazoguaiacol ,, 
Benzeneazothymol 
„ -a-naphthol 
4-sulphobenzeneazo-a-naphthol (alkali) 
Benzeneazo-tetrahydro-a- „ 
,, -catechol 
4-diphenylylazophenol ,, 
Diphenyltetrazo-^-phenolsulphonate (alkali) 
4-N0 2 C 6 H 4 CH : NC 6 H 4 OH 
4-N0 2 C 6 H 4 N : CHC fl H 4 OH 
4-N0 2 C 6 H 4 CH : NC 10 H c OHa 
4-N0 2 C 6 H 4 N : CHC 10 H 6 OHa ,, * 
4-diphenylylazonaphthionic acid (in HC1) . 
Congo-red (in HC1) ..... 
XX 441 and 390. 
X 480 broad single. 
X 475 broad = XX 491+460 in 
weaker acid. 
X 493 broad single. 
X 455 
XX 430+384. 
XX 436+390. 
XX 487+440. 
X 490 broad single. 
X 576 broad = XX 602 + 552, 
X 598 „ =XX 623+572. 
X 502 ,. =XX 540+490. 
X 440 and ? 400. 
XX 445 + 395. 
XX 447 + 390. 
X 463 single. 
I 475 „ 
X 460 broad single. 
XX 455+410. 
X 496 broad single. 
X 513 „ 
XX 470+430. 
XX 480+430. 
X 451. 
X 475 broad single. 
X 455 
X about 410. 
XX 560 + 505 in alcohol. 
XX 510 ( + 545 taint) in alcohol. 
X 575 broad single. 
X 580 
From these we infer (1) that the ordinary substitutions have about the 
same small effect as in the dicyclic series : paranitro and naphthyl have the 
largest factors = 1-16 and 1-19 respectively ; (2) the benzidine dyes are 
practically the same as the diphenylyl dyes, i.e. only half the molecule acts. 
* I have to thank Professor G. T. Morgan for this specimen (J.C.S., 1922, p. 5). 
