TRANSACTIONS OF SECTION RB. 511 
were obtained ; they are colourless, and doubtless possess a lactonic constitution. 
Only when the neutral sodium salts of the two phthaleins are treated two new 
compounds are formed, in addition to the well-known di-ethers. These substances 
proved to be the mono-ethers, C,,H,,0,,0CH, and C,,H,,0,OCH,, and are not 
carboxylic but hydroxylic ethers; they could not be saponified, and on further 
treatment with alkyl salts yielded the lactonic ethers, They do not decompose 
sodium carbonate, and hence do not contain a free carboxyl group; moreover, 
they are colourless, and are doubtless of lactonic constitution, just as are the 
di-ethers. They form, however, red salts, the constitution of which is open to 
discussion. 
The quinonoid formulz of the phthaleins indicate the presence of one carboxyl 
and one phenolic hydroxyl group in the molecule, whilst, according to the lactonic 
formula, two phenolic hydroxyl groups are present. The etherification conditions 
of carboxylic acids and phenols were therefore studied, as it appeared of prime 
importance to ascertain whether the carboxyl group can be esterified under the 
conditions prevailing in the present experiments—namely, in neutral or alkaline 
solution. The following facts were established as the result of numerous experi- 
ments, carried out under a great variety of conditions. Phenol is always converted 
into its ethers by means of alkyl halogen salts and by methyl sulphate, whether 
the solution be alkaline or neutral, or even acid; the only point of difference is in 
the yield obtained. Benzoic acid, however, can only be esterified in acid or 
neutral solutions, but not in alkaline ones, whether alkyl halogen salts or methyl 
sulphate is used. 
It would seem difficult to reconcile the above results with the quinonoid 
formula of the phthalein salts; the difticulty involved in the assumption of the 
quinonoid theory is also felt by A. G. Green and A. G. Perkin, and they attempt 
to overcome it by assuming the intermediate formation of the carbinol salt. This 
view would indicate that the red solution contains, in addition to the quinonoid 
salt, a certain proportion of carbinol salt, from which latter the lactonic ethers 
are produced; and that during the course of the reaction the quinonoid salt is 
progressively converted into carbinol salt, in accordance with the law of mass 
action, until the change has become complete. The carbinol salt could only be 
formed by opening the ring, and this could only take place whilst working in 
presence of excess of alkali; since, however, the author has obtained the same 
Jactonic di-ethers in neutral solution, the opening of the lactonic ring in this case 
would appear to be impossible. 
The advocates of the quinonoid theory point to analogies between phenol- 
phthalein and fluorescein, but the author is of opinion that it would be very difficult 
to find, in one group of chemically related compounds, two substances more dis- 
similar than are phenolphthalein and fluorescein. Thus, for instance, R. Nietzki 
and P. Schroeter obtained one lactonic and three quinonoid ethers by the 
* alkylation of fluorescein, whilst the salts of phenol- and quinol-phthalein never 
yielded quinonoid derivatives under the most varied conditions of working. The 
quinonoid ethers of tetrabromophenolphthalein, discovered by R. Nietzki and E. 
Burckhardt, have no bearing on this question, because they have not been pre- 
pared from the phthalein salts. It would be preferable to try to express the 
different behaviour of fluorescein and phenolphthalein by the aid of chemical 
formule rather than to insist on a similarity which is not warranted by the facts. 
One serious difficulty arises in connection with the colour of the alkali salts: 
Ostwald assumes that the red colour is due to the phthalein ions, whilst the 
undissociated molecules are colourless. If, however, the ions are coloured, they 
should contain a chromophoric group, such as is present in undissociated coloured 
molecules; the lactonic formula does not indicate the presence in the molecule of 
such a chromophoric group. At the same time, it must be agreed that, however 
valuable the theory of chromophors has proved as a means of characterisation and 
classification of colouring matters, it is not sufficiently comprehensive to include 
all coloured organic compounds. It does not include the quinolphthaleins (and 
orcinphthalein), dibenzalacetone, and other colourless substances which form deeply 
coloured addition compounds with mineral acids. Adolf Baeyer introduced the 
