Part 5

These analyses show with but little doubt that the substance has the composition indicated above i.e. C{19}H{12}O{6}S+2H{2}O. The reaction therefore which takes place between ortho-sulpho benzoic acid and resorcin from its analogy to that taking place between phthalic anhydride and resorcin may be represented thus, as shown by Baeyer in his second paper (Ann. 202. S. 43)

Representing the formation of the anhydride as the first action.

COOH CO ╱ ╱ ╲ C{6}H{4} = C{6}H{4} O + H{2}O \ ╲ ╱ SO{2}OH(o) SO_{2}

and the action of resorcin on this anhydride thus.

CO OH ╱ ╲ ╱ C{6}H{4} O + 2C{6}H{4} ╲ ╱ ╲ SO_{2} OH (m)

O ╱ ╲ (HO)H{4}C{6} C{6}H{4}(OH) ╲ ╱ = C + 2H{2}O ╱ ╲ C{6}H{4} O ╲ ╱ SO{2}

The substance thus formed would naturally receive the name Sulphonfluoresceïn from its analogy with Fluoresceïn.

┌─ │ OH │ ╱ │ C{6}H{3} │ ╲ │ O │ ╱ C ─┤ C{6}H{3} │ ╲ │ OH │ │ C{6}H{4}SO_{2} │ ╱ │ O └─ Sulphonfluoresceïn.

┌─ │ OH │ ╱ │ C{6}H{3} │ ╲ │ O │ ╱ C ─┤ C{6}H{3} │ ╲ │ OH │ │ C{6}H{4}CO │ ╱ │ O └─ Fluoresceïn.

Properties of S.fluoresceïn.

This compound shows a marked similarity to the fluoresceïn described by Baeyer as would naturally be expected from its great similarity of composition and constitution, but it also shows decided differences which may be attributed to the replacement of CO by SO_{2}.

Dissolved in water it shows a weak green fluorescence which in alkaline solution becomes much deeper but not by any means so strong as that of fluoresceïn. The dilute alkaline solution by transmitted light is almost perfectly colorless and by reflected light a clear green. Unlike fluoresceïn it is extremely soluble in water, about one part in two or three of hot and five or six of cold water. It is also soluble in absolute alcohol forming a yellow solution with weak fluorescence. It is soluble with difficulty in ether but when in solution is deposited only on evaporating to a small volume.

It does not melt at 250° but if held at a lower temperature for a long time becomes red undergoing some decomposition. If quickly heated somewhat above 300° it melts to a deep red liquid and then solidifies. If the mass is treated with water it partly dissolves leaving a dark brown flocculent precipitate which dissolves on the addition of an alkali, the solution having an intense fluorescence, nearly if not quite equaling that of fluoresceïn. This change produced by heating was not further studied.

The crystals are very thin blades, apparently monoclinic, showing the clinopinacoid αΡὰ and a very narrow prism αΡ and clinodome Ρὰ. The angle β = 75° and the extinction angle against the ϲ axis = 20°. The axial ratio could not be accurately determined.

Salts of sulphonfluoresceïn.

The influence of the SO_{2} group is shown by the fact that the substance acts as an acid decomposing carbonates and forming salts which is not the case with fluoresceïn.

Barium salt.

The substance was boiled with an excess of carefully purified BaCO{3} for two hours. The filtrate from the BaCO{3} evaporated to a small volume deposited yellow crystals resembling the original substance but in shorter and thicker prisms. These were twice recrystallized and had then a light straw yellow color.

A determination of the Ba gave the following results. The salt was dried in the air.

All these calculations are wrong. J.R.]

I ·1078 gr salt gave ·0304 gr BaSO_{4} = 15·73% Ba. II ·1641 ” ” ” ·0457 ” ” = 15·53” ” III ·2425 ” ” ” ·0680 ” ” = 15·65” ” IV ·2860 ” ” ” ·0798 ” ” = 15·54” ” V ·1843 ” ” ” ·0498 ” ” = 15·08” ” VI ·2620 ” ” ” ·0708 ” ” = 15·08” ” VII ·3230 ” ” ” ·0906 ” ” = 15·65” ” VIII ·2875 ” ” ” ·0807 ” ” = 15·66” ”

Calculated for C{19}H{13}O_{7}SBa = 15·10% Ba.

In the above determinations the salt analysed was taken from specimens made at three different times and purified in slightly different ways, Nos 1, 2, & 3 being washed with absolute alcohol. Nos V and V were made by precipitating the Ba with H{2}SO{4} from a solution of the salt.

The water was determined by heating at 110° till constant weight was reached. Part only of the weight lost was regained on standing in the air.

·3943 gr salt lost at 110° ·0286 gr = 7.25%

Water calculated for C{19}H{13}O{7}SBa+2H{2}O = 7.35%

Although these analyses show a per cent. of Ba somewhat above that required by a compound having the formula C{19}H{13}O{7}SBa still this appears to be the most probable formula which can be assigned to the substance. If this is the true composition of the salt, then in sulphonfluoresceïn the anhydride condition must be broken up by boiling with BaCO{3} forming the salt thus.

┌── ──┐ ┌── ──┐ │ │ │ │ │ ┌─ OH │ │ ┌─ OH │ │ │ / │ │ │ / │ │ │ C{6}H{3} │ │ │ C{6}H{3} │ │ │ \ │ │ │ \ │ │ │ O │ │ │ O │ │ │ / │ │ │ / │ │ C ┤ C{6}H{3} │ │ │ C{6}H{3} │ │ │ \ │ + H{2}O = │ C ┤ \ │ │ │ OH │ │ │ OH │ │ │ │ │ │ │ │ │ C{6}H{4}SO{2} │ │ │ C{6}H{4}SO_{2}OH │ │ │ / │ │ │ │ │ └─ O │ │ └─ OH │ │ │ │ │ └── ──┘ └── ──┘