Attempts were made to prepare the calcium salt but without success. The S-fluoresceïn was boiled several hours with very finely powdered calcite, and some salt was formed as shown by the CO_{2} evolved but on evaporating the solution and recrystallizing the substance deposited it was found to be the unchanged S-fluoresceïn. Some Ca. salt was in the mother liquors but its extreme solubility prevented a separation being made. Acetyl derivative of S.fluoresceïn. S.fluoresceïn was boiled with an excess of acetic anhydride for about three hours. The solution became quite dark and when evaporated on the water bath left a black tarry residue. This was treated with water which dissolved a part leaving a dark flocculent precipitate. The solution was boiled with animal charcoal and evaporated nearly to dryness. On cooling there separated a light yellow flocculent precipitate very soluble in hot water and but slightly less so in cold. This was dissolved in a small quantity of alcohol from which it separated on evaporation in small radial crystals having a light lavender color & satiny luster. They also have a peculiar odor resembling slippery elm which is not removed by recrystallization. They show a tendency to decompose, becoming yellow on exposure to the air. The substance does not melt or change in appearance under 245°. With alkalis it gives a slight greenish fluorescence. From the method of its formation this was taken to be an acetyl derivative of S.fluoresceïn but whether the mono-or di-acetyl could not be determined without analysis for which the substance did not suffice. Bromine substitution products of S-fluoresceïn. It was especially interesting to see what influence the SO_{2} group would exert upon the introduction of Bromine into the compound. In the case of fluoresceïn four Bromine atoms enter easily and special precautions are necessary to obtain a product containing a smaller number. The case however is different with S.fluoresceïn. The latter was dissolved in glacial acetic acid in which it is soluble with some difficulty and to the solution was added a 20% solution of bromine in acetic acid, in sufficient quantity to make eight atoms of bromine to one molecule of S.fluoresceïn. This solution was evaporated on the water bath and while still having a considerable volume, small, red, sharply defined crystals began to separate. The solution was evaporated to a small volume and allowed to cool but nothing further separated. These crystals are difficultly soluble in water, alcohol and ether. The alkaline solution shows a green fluorescence and slight red color by transmitted light. These crystals were dissolved in a large quantity of alcohol which on evaporation gradually deposited very small yellow crystals, which were dried in the air and taken for analysis. The Br. was determined by Carius method. I. ·2345 gr sub. gave ·1718 gr AgBr = 31·17% Br. II. ·2786 gr ” ” ·1815 gr ” = 27·72% Br.