The principal results relating to s.fluoresceïn which have been reached in this work may be briefly summarized as follows. Orthosulphobenzoic acid acts on resorcin at a temperature of about 180° giving off water and forming a substance analogous to fluoresceïn but having the CO group replaced by SO_{2}. This substance sulphonfluoresceïn crystallizes from water in light yellow monoclinic crystals having the composition C_{19}H_{12}O_{6}S+2H_{2}O. It is very soluble in alcohol and water and with difficulty in ether. It does not melt under 250° but above 300° melts with decomposition. It shows in alkaline solution a clear green fluorescence. It acts as an acid, decomposing carbonates and forming salts, the Ba salt having the composition C_{19}H_{13}O_{7}SBa. It forms an acetyl compound when boiled with acetic anhydride. It forms substitution products with Br, probably the dibrom-product most easily. It forms a compound with H_{2}SO_{4}, probably a substitution product, whose composition was not determined. It is reduced by zinc dust and KOH to a colorless substance analogous to fluoresceïn. Finally in terms of the prevalent theory the substance itself may be represented thus-- H H ┌─ C O C │ ╱ ╲ ╱ ╲ ╱ ╲ │ OH (HO)C C C C(HO) │ ╱ │ │ │ │ │ C_{6}H_{3} HC C C CH │ ╲ ╲ ╱ ╲ ╱ ╲ ╱ │ O C C C = C ──┤ ╱ H ╱ ╲ H │ C_{6}H_{3} HC ╱ ╲ │ ╲ ╱ ╲ ╱ ╲ │ OH HC C O │ │ │ ╱ │ C_{6}H_{4}SO_{2} HC C ╱ │ ╱ ╲ ╱ ╲ ╱ │ O C SO_{2} │ H └─ End of the Project Gutenberg EBook of On Sulphonfluoresceïn and some of it Derivatives, by C. Willard Hayes