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Sandaracopi~naric acid has been shown to be 7-epipimara-8(14),18-dienoic acid (II), and Ukita's acid to be T-epi-13p-pin1ara-9(14),18-dienoic acid (VI). A hydroxyl-containing acid from Sandarac resin is described.Sandaracopimaric acid was isolated by Henry (1) and by Tschirch and Wolff (2) from the resin of the N. African sandarac tree (Callitris qz~adrivalvis). Recently an improved isolation procedure was described by Petru and Galilc ( 3 ) , who also demonstrated that the acid belonged to the pi~naric group. They claimed (4) that both pimaric acid and sandaracopilnaric acid gave the sanle partial dehydrogenatio~l product I and hence had the sanle configuration at C-7. Even if this conclusion had been correct their xvorlc left the location of the double bond and the stereoche~nistry a t the other a s y~n~n e t r i c centers unlcnown. I n continuance of our interest in the stereochemistry of the pi~naric acids3 we have examined sandaracopirnaric acid, and proved it to be the C-7 epi~ner (11) of pimaric acid (7-epipimara-8(14) ,18-dienoic acid) .4Using the ~nethocl of Petru and Galilc (3) we obtained an ether-soluble anlrnoniu~n salt fro111 the resin. This was co~lverted into the sodium salt, which was then precipitated from its aqueous solution by addition of concentrated sodium hydroxide solution. The precipitate did not crystallize readily, so the acids liberated from it were chromatographed on silica gel. In this way a 2.2% yield of sandaracopimaric acid and a 1.3% yield of a higher ~nelting acid were obtained. The latter had m.p. 270" and [a],, -11" in ethanol.\

A s+inaLl and Nicolson. 2503 505. The Catalytic Oxidation of European Larch E-Galactan?By G. 0. ASPINALL and A. NICOLSON.Catalytic oxidation of larch E-galactan results in selective oxidation of primary alcoholic groups with the formation of carboxylic acids. Graded hydrolysis of the oxidised polysaccharide gives two aldobiouronic acids, (6-~-galactose p-D-galactopyranosid)uronic and (6-n-galactose L-arabinofuranosid)uronic acid. The structural significance of these and other results is discussed.

The effects of oxygen concentration on the stability of methacrylic acid ( M A A ) have been examined using HQ, MeHQ and PTZ as inhibitors. The O2 has been found to have a dual effect so that an optimum concentration confers very high stability but increased [O,]s give significantly reduced induction periods, especially at higher temperatures. This behavior has been explained in terms of radical scavanging competing with peroxide formation and cleavage. The main parameters controlling the system have been examined. The rate of stabilizer consumption was found to be controlled mainly by temperature and [O,]. The rate of energy release on polymerization is dependent on temperature, [stabilizer] and 0, supply to the system and is rapid (violent in extreme cases) only when all three factors are favorable for efficient peroxide formation and cleavage. Preliminary experiments with n-butyl methacrylate indicate that the same principles and mechanism operate for the simple methacrylate esters. ~ ~~~~ ~~~~ ~ ~~ ~~ ~~~ _________ Plantloperations Progress (Vol.

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