Colour and Chemical Constitution. 
125 
stituent instead of p-cresol. The heating must be carefully conducted so as 
to stop short of the evolution of COg from the carboxjlic acid. 
The new phthalein gives only a faint colour in ammonia, a stronger base 
being required to give the highly-coloured phenolic salt in which both the 
— COgH and the —Oil groups are combined with alkali. The colour is 
violet-pink, the absorption-band being at ?^ 562 in very weak alkali and at 
A 570 in strong alkali, and intermediate strengths give intermediate posi- 
tions. In cone. II0SO4 the colour is yellowish-salmon, and the absorption- 
band at X 502. 
An attempt to make its methyl-ester, starting with methyl |)-oxybenzoate, 
apparently gave the same product, the ester being too easily hydrolysed. 
The methyl- ether, however, was obtained in small quantity by condensing 
anisic acid with jj-oxybenzoylbenzoic acid. It is pink in alkali, bleaching on 
short standing. The absorption-band is at a 558 and the one in H2SO4 is at 
A 503. The close resemblance to oxydiphenylphthalide, of which it is a 
simple derivative, may be noted. 
A still simpler derivative of oxydiphenylphthalide, viz. its carboxylic 
acid, was made for comparison by condensing benzoylbenzoic acid with 
salicylic acid. The resulting oxydiphenylphthalide carhoxylic acid is colourless 
in ammonia and pink m caustic alkali (a 562 in weak and 566 in strong). 
It is yellow in HoSO^ with band at X 489. Oxydiphenylphthalide itself gives 
\ 560 in alkali and x 482 in H0SO4. The formulae of the last two substances 
are respectively : 
I J0CH3 ■ I J 
\y COoH \/ 
H0<^ \—C-<( and I10(^ \—^-\ ^ 
\ ^ I \ / \ / I \ / 
0/CO 0/CO 
The following other derivatives of o-j^-plienolphthalein were made for 
spectroscopic observation : 
(1) m-am.ino-o-^-phenolphthalein, from jj-aminophenol : colour in alkali 
bottle-green ; broad absorption -band with centre at about A 575. 
(2) m-methylamino-derivative, ivom " metol " base: colour in alkali as 
above ; absorption-band covers most of red, but centre is near \ 640. 
(3) i^- carhoxylic acid of foregoing, from " glycin " (developer) : colour 
olive with almost whole of red absorbed. 
(4) m-phenyl-derivative, from diphenylol (^^-phenylphenol) : colour blood- 
red with green fluorescence ; no definite absorption. 
(5) m-nitro-derivative, from j:)-nitrophenol : maroon in alkali with broad 
band at \ 558. 
By means of the corresponding m-iodo-o-j>phenolphthalein (made from 
