(2,3-dihydro-4-nitro-2,3-dioxo-9,10- secosrychnidin-10-oic acid) [ 561-20-6] M 508.4, pK _Est(1) 4.4 (CO ₂H), pK _Est(2) 10.2 (N). Yellow crystals from H ₂O. It is then dried over H ₂SO ₄ which gives the dihydrate, and in a vacuum over H ₂SO ₄ at 105 to give the anhydrous compound. The hydrochloride separates as the hydrate (on heating in vacuum at 80 ) in orange-yellow prisms or plates, m 250 (dec), and forms a resorcinol complex which gives brown crystals from EtOH, m 325 , and a hydroquinone complex as dark red crystals from EtOH, m 319 . [ Chem Ber 43 1042 1910, 86 232, UV: 242 1953; complexes: Gatto Gazz Chim Ital 85 1441 1955.] Used in the titrimetric estimation of Sn ²⁺ ions [Szrvas and Lantos Talanta 10 477 1963].

Caffeic (3,4-dihydroxycinnamic) acid [ 331-39-5] M 180.2, m 195 , 223-225 , pK ²⁵ ₁ 4.62, pK ²⁵ ₂9.07 Crystd from water.

Caffeine [ 58-08-2] M 194.2, m 237 , pK ⁴⁰ ₁ -0.10, pK ⁵⁵ ₂ 1.22. Crystd from water or absolute EtOH.

(+)-Calarene (+ ?-gurjunen, 1,3,3,11-tetramethyltricyclo[5.4.0.0 ^2,4]undecan-7-ane, (1a R)-1,1,7c,7ac-tetramethyl-1a,2,3,5,6,7,7a,7b-octahydro-1H-cyclopropa[ ?]naphthalene, new name 1(10)aristolene) [ 17334-55-3] M 204.35, b 45-47 /0.008-0.01mm, 255-258 /atm, d ²⁰ ₄ 0.9340, n ²⁰ _D 1.55051, [ ?] ²⁰ _D