Colour and Chemical Constitution. 
13 
Table III. 
Spectra and Colours of Phthaleins in cone. HgSO^ Solution. 
A. Phthaleins : constant 4'55, 
No. 
Name. 
Frequency in 
Alkali = X. 
in H2SO4 
observed = y. 
Colour. 
Calculated 
Value of y. 
Jr nsnoipntnaiein 
18*05 
20'20 
feaimon-yeiiow 
-> 
Phenolphthalein me- 
\j<j 
90-1 ft 
thylether 
3 
4-oxyphenolphthalein . 
18-45 
20-80 
20-85 
4 
Phenoltetrabromoph - 
17-70 
19-95 
19-73 
thalein 
5 
0-cresolphthalein 
17-50 
19-65 
Pink 
19-43 
g 
Dibromo-o-cresolph- 
17-30 
18-85 
Xtj LO 
thalein 
1 
Tetrabromophenol- 
17-15 
18-90 
phthalein 
Thy molphthalein 
16-75 
18-25 
Purplish-pink 
XO o\j 
q 
Carvacrolphthalein 
16-65 
18-05 
1 ft-1 
Xo XO 
10 
Octobromophenol- 
16-45 
17-95 
Purple 
17-85 
phthalein 
±x 
Thymoltetrabromo- 
16-05 
17-40 
Bluish -purple 
17-25 
phthalein 
12 
a-naphtholphthalein . 
15-10 
15-80 
Bluish- green 
15-82 
13 
a-naphtholtetrabromo- 
14-75 
15-30 
Green 
15-30 
phthalein 
j _ 
B. Fluoresceins : constant 4"7. 
1 
3 oxyflnorescein . 
20-45 
23-8 
Yellow 
23-6 
2 
Phloroglucinph thalein 
20-15 
23-1 
23-2 
3 
Fluorescein 
20-05 
23-2 
23-0 
4 
Eesorcinbenzeine 
19-95 
22-6 
22-9 
5 
Iso eosine . 
19-90 
22-8 
Yellowish- 
22-8 
salmon 
6 
Eosine 
19-35 
21-9 
22-0 
^ 7 
Erythrosine 
1905 
21-35 
21-5 
! 8 
Gralleine 
18-4 
21-5 
20-6 
C. Some other Fuchsone-derivatives which do not follow the above law. 
Aurine 
18-90 
20-8 
Salmon 
^; 
Benzaurine . 
17 55 
21-7 
Yellow- salmon 
C. 
Diethylrhodamine 
18-10 
21-8 
D. 
Quinolphthalein . 
20-25 
20-1 
Salmon 
E. 
Eesorcinolphenyl- 
Violet only 
20-25 
phthalein 
The absorption bands in H2SO4 of the following substances are : Fluorane, 20"05 ; 
fuchsone, 22-0; benzophenone, 21-7; benz-naphthaurine and its — COgH derivative 
(from BBA and naphthol), both 17-6. 
and, what is remarkable, that the intensity of the colour is about five times 
as great as when they are dissolved in alkali. The colours obtained in the 
two cases are not identical ; thus, all the phthaleins giving a blue colour in 
alkali give a pink colour in H2S0^. In addition, many other substances of 
