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COLOUR AND CHEMICAL CONSTITUTION. 
Part XVI. — Further Miscellaneous Observations. 
By James Moir. 
The main lines of the theory of the colour of " cyclic " coloured sub- 
stances having been established in Parts X, XIII, and XIV, it only remains 
to put on record observations of the absorption wave-length of all the 
" monocyclic " and " di cyclic " colours which I have used in making the 
discovery, but have not published for fear of overloading these theoretical 
papers with unnecessary detail. 
A. Derivatives of the Prototype Colours. 
1. Orthopara- or (2-4')-dioxybenzhydrol, from salicylaldehyd (see 
Beilstein, ii, 1114). This has A 543 (broad) in alkali, A 486 in HC1, and 
A about 495 when in suspension in neutral water. The isomeric ^-^-corn- 
pound has A 539 in dilute alkali, but in HC1 has the same A as the o-p- 
compound. 
2. 2-oxy-4'-dimethylaminobenzhydrol, from salicylaldehyd and di- 
methylaniline, has A 561 (broad) in alkali, with A 500 in HC1. The isomeric 
4-4'-compound has A 572 in alkali and A 504 in acid. This was predicted 
(as A 571) in Part XII, top of p. 211. 
3. 2-4-4'-trioxybenzhydrol, from j9-oxybenzaldeliyd and resorcin, 
appears to have A 494, whereas A 550 was expected : possibly the reaction 
is abnormal. 
4. 2-4-dioxy-4 / -methoxybenzhydrol, from anisaldehyd and resorcin, has 
A about 380 in alkali. This substance appears to be monocyclic, since 
2-4-dioxybenzhydrol has a similar A. 
5. 2-4-dioxy-3'-4'-dimethoxybenzhydrol-2'-carboxylic acid, from opianic 
acid and resorcin, has A 390 in alkali. This is also monocyclic, being a 
derivative of monophenolphthalein (Part XIII, p. 38). 
6. Mono-a-naphtholphthalein, from phthalaldehydic acid and a-naphthol, 
has A 370, and is also monocyclic. 
