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All the isomeric thionaphthencarboxylic acids, except thionaphthen-4carboxylic acid, have been synthesised. Most of these syntheses involve intermediate formation of bromothioindoxyls by ring closure from the appropriate orth-substituted (bromophenylthio) acetic acids. Ring closure was facilitated by the presence of a formyl group or its equivalent in the ortho-position to a carboxyl or cyano-group.

The thermal destruction of riboflavin in buffer solutions from pH 0.5 to 12.0 has been studied by ll'teans of fluorimetric analysis and the application of the first-order reaction and Arrhenius equations. The buffer solutions used were a modified universal buffer (phosphate, borate, acetate), McIlvaine's citric acidphosphate buffer, veronal-HCI, and glycine-NaOH.

The successful degradation and synthesis of the accessory food factor variously known as vitamin Be, L. casei factor, S. lactis R factor, folic acid and, finally, pteroylglutamic acid (Angier et al., 1946) has not only given rise to more exact work on the significance of this vitamin in anaemia of different kinds, hut has also enabled a more precise standardization of the microbiological assay of the factor to be made. Such assay, of course, involves the heat sterilization of the standard test solutions containing folic acid and, as little is known of the thermal stability of this vitamin, this study was undertaken. The first step was to establish the relation between pll and recovery ol" adiletl folic acid at temperatures of 100° and 121° C. (15 Ib. steam pressure), concurrently investigating the effect of various buffer solutions. The second step was to study the kinetics of the thermal destruction demonstrated. EXPERIMENTAL. MATERIALS. Folic acid 3torJ: solution.Synthetic pteroylglutamic acid ("Folvitc" ot Lederle Laljoratories) was used. 10 mg. were dissolved in distilled water by steaming and made up to 2 litres. Later a 50 p.c. water-alcohol mixture was used to dissolve Ihe "Folvite". 1 ml. ot atock solution contained 5jig. of *'Folvite". Buffer Solutions.(a) Sodium Acetate-Bydrochlori^; Acid. AIM sulution of sodium acetate was prepared in distilled water. For most experiments 10 ml. were diluted to about 40 ml. and the pH adjusted to the desired value with 6 N HCl. The volume was then miade up to 50 ml. In preparing larger volumes 50 ml. of acetate after pH adjustment were made up to 250 ml.(b) Sodium Phoaphatc-Cilric Acid. Solutions of 0*1 M citric acid and 0-2 M disodium hydrogen phosphate were prepared. Varying volumes of tho one were made up to 50 ml. with the other to yield the desired pH. Any final adjustment was made with 6 N HCl or 10 p.c. NaOH.(c) PhoNphate-Phthalatc. 10 ml. of a solution 0-5 M with respect to both potassium dihydrogen phosphate and potassium hydrogen phthalate were diluted to about 45 ml., the pH adjusted to the desired value with NnOII solution and the volume made up to 50 ml.(d) Glycine-Sadluvi Hydroxide. A solution of glycine (0-1 M) was prepared in 0-1 N NaCl solution and varying volumes as required were made up to 50 ml. with 0*1 N NaOH,