226 
Transactions of the Royal Society of South Africa. 
orthochlorophenol, or by cautious chlorination of phenolphthalein in cold 
dilute alcohol. The 2-6 derivative is obtained either from 2>-oxybenzoyl- 
benzoic acid and 2-6 dichlorophenol, or from phenol with 3-5 dichloro- 
4-oxybenzoylbenzoic acid,* the latter substance being obtained by splitting 
tetrachloro-phenolphthaleiu with hydroxylamine in the same way as 
oxybenzoylbenzoic acid is obtained from phenolphthalein (see Part II). 
Only one o-trichloro-phenolphthalein can exist ; this has not been made 
but its absorption-band is predicted to be at a 576. 
Table A. 
Spectrum 
JSTame of coloured substance. i 
centre of 
absorption 
band. 
Value 
of m. 
Value 
of N. 
Calculated 
frequency. 
Calcu- 
lated \. 
Tetrachloro-phenolphthalein . 
A 583 
17 
1715 
583 
Tetrabromo- 
X584 
4 
35 
1711 
584i 
Tetriodo- „ 
A 586 
4 
53 
1707 
5851 
Tetrachloro-fluorescein . 
A 519 
4 
17 
19-26 
519 
Tetrabromo- (eosin) . 
X521 
4 
35 
19-21 
520-.} 
Tetriodo- „ (erythrosin) 
A 523 
4 
53 
1916 
522 
o-dibromo-phenolphthalein 
(A 569 (a)] 
1a 570 (b) \ 
2 
35 
17-60 
569 
2-2^ dibromo-fluorescein . 
A 508 
2 
35 
19-73 
506i 
o-Monochloro-phenolphthalein. 
A 560 
1 
17 
17-84 
561 
o-Dichloro-phenolphthalein 
(A 570 (a)] 
(A 569 (h)\ 
2 
17 
17-62 
568 
2-6 dibromo-2' methyl deriva- 
tive ..... 
A 573 
2 
35 
17-35t 
576 
2-6 dibromo-3' methyl deriva- 
tive ..... 
A 584 
2 
35 
1712; 
584 
[Tetriodo - tetrachloro - fluores- 
a548§ 
(4 
17 plus) 
53 I 
18-16 
cein ..... 
14 
550] 
Of the isomeric dihalogen derivatives it may be noted that the 2-6 variety 
is easily bleached by excess alkali, whereas the 2-2^ variety resists alkali to 
some extent. 
On perchlorination of phenolphthalein in warm chloroform solution a 
small quantity of a product giving an emerald- green solution in alkali was 
obtained. The central wave-length of the band was X 642, from which it 
may be inferred that it is probably decachloro-phenolphthalein. The 
* This substance gives an orange-coloured solution in strong sulphuric acid, with 
an absorption-band at X 472. 
t Calculated from lY'SO, the frequency of phenolortho-cresolphthalein. 
X „ „ 17-57 „ „ phenolmeta-cresolphthalein. 
§ Taken from ' Chemiker Kalender ' ; not personally observed. 
