Part 7

On cooling, the product was powdered and treated with dilute alkali. It readily dissolved, without residue, forming a dark red solution. In concentrated solution the addition of acid produces a voluminous precipitate, dark brown in color, which when washed, and dried in paper forms an almost black powder. A dilute solution of this powder is dark red when alkaline, orange-yellow when acid.

From the way in which this powder was obtained, and owing to the fact that its solubility prevented repeated washing, it was evident that it would not give close analytical results for a calculated formula. It was thought, however, that analysis would give a general idea of the composition.

Analysis of different specimens gave results for sulphur which averaged about 5.5%. The percentage required for the formula

C[C₆H₃(OH)₂]₂ / \ / O / / C₆H₃——SO₂ \ NO₂

which represents the simplest sulphonfluoresceïn, is 7.43.

The compound could hardly have been so far from pure as to occasion such a discrepancy in results as this. It would appear, therefore, that more than two molecules of hydroquinone enter into the reaction with one molecule of the chloride. Should four molecules be involved in the reaction, leading to a compound of some such formula as

C[C₆H₃(OH)₂] / \ / O / / C₆H₃——SO[C₆H₃(OH)₂]₂ \ NO₂

the theoretical percentage of sulphur would be 6.00 which corresponds much more closely with the results obtained.

This is in accord with the observations of a number of workers in this laboratory—Lyman, Gilpin, Linn and others—who have worked on various sulphonfluoresceïns, and have found that in many cases four, six and even eight phenol residues condense with one molecule of the anhydrous acid. Lyman especially describes a tetra hydroquinone sulphonfluoresceïn derived from orthosulphoparatoluic acid. No etherial salt was observed.

Am. Chem. Journ. XVI-525

5. The Action of Resorcin upon the Symmetrical Chloride of Paranitroorthosulphobenzoic Acid.

The reaction of resorcin with the chloride is a much cleaner one and proceeds more easily than in the case just described, leading apparently to an individual compound which is well characterized.

During the reaction, which is complete at 125°, the mixture becomes almost perfectly solid, and when cool, it is quite brittle. It was reduced to a reddish powder in a mortar and dissolved in sodium hydroxide, there being no insoluble residue. By the addition of hydrochloric acid, the sulphonfluoresceïn was thrown down as a chocolate-brown precipitate, which was filtered off, washed to neutral reaction on a filter, and dried on paper. In this condition it is a light chocolate-brown powder. In dilute alkaline solution it possesses a slight fluorescence being pink by transmitted and yellow be reflected light, suggesting eosin in a general way. It is interesting to note that the sulphonfluoresceïn of orthosulphobenzoic acid possesses a fluorescence that can hardly be distinguished from ordinary fluoresceïn and that the introduction of a nitro group into the acid residue produces much of the same effect as do the four bromine atoms in eosin. In acid solution the color is reddish-orange.

Analysis of the compound, prepared as above described, gave the following results.

I. 0.1745 gram gave 0.3339 gram of CO₂ and 0.059 gram H₂O.

II. 0.1467 gram gave 0.2820 gram CO₂ and 0.0432 gram H₂O.

III. 0.1732 gram gave 0.3345 gram CO₂ and 0.0571 gram H₂O.

IV. 0.2000 gram gave 0.1104 gram BaSO₄.

V. 0.1505 gram gave 0.0820 gram BaSO₄.

OH ] / ] C[C₆H₃ ] / \ \ ] / O OH ]2 / / Cal. for C₆H₃——SO₂ \ NO₂ Found I II III IV V C = 52.66 52.18 52.42 52.67 —— —— H = 3.46 3.76 3.27 3.66 —— —— S = 7.39 —— —— —— 7.57 7.48

An effort to obtain the anhydride was unsuccessful. Some loss of weight was observed, but the compound underwent decomposition before this loss amounted to much.

6. The Action of Pyrogallol upon the Symmetrical Chloride of Paranitroorthosulphobenzoic Acid.

The product of this action dissolves readily in dilute sodium hydroxide without residue, producing a very deep purple-black color when concentrated, passing to grayish-violet as the solution is diluted. On adding hydrochloric acid, precipitation occurs, as in most of these reactions. On attempting to filter off this precipitate, it forms a sticky, black mass on the filter with which little can be done. It is best to evaporate to dryness before filtration and powder the residue. This powder can then be washed fairly clean from alkali salts and acid.

Nothing to suggest the formation of an etherial salt was observed.

Analysis of this product for sulphur showed that in this galleïn, as in the case of the hydroquinone phthaleïn more than two pyrogallol residues had entered the acid residue. The indications were that six had entered into one of the chloride. This also agrees with the observation of Lyman, who describes a hexapyrogallol galleïn of orthosulphoparatoluic acid.

Probably a mixture of varying composition was obtained, and little importance was attached to the results save as they showed that no etherial salt is formed in the reaction.

Am. Ch. Journ. XVI-527.

7. The Action of β-Naphthol upon the Symmetrical Chloride of Paranitroorthosulphobenzoic Acid.