CCCCII1.-Oxidation of Ethyl Ether to Oxalic Acid in Presence of Uranyl Nitrate. By SYDNEY WILLLAM ROWELL and ALEXANDER SMITH RUSSELL. WHEN uratnyl nitrate dissolved in ether is exposed to sunlight in presence of water a yellow precipibte sometimes forms in the aqueous layer especially after the solution has been standing in tJhe light for some days; at other times a black slimy mass forms in the aqueous layer. These compounds are the subject of the present investigation. There is only one reference in the literature to the composition of the yellow compound (Soddy “Chemistry of the Radioelements,” 1911 p. 32). Soddy found that a yellow powder of empirical formula UCH40 remained after distilling the ether from an ethereal solution of uranyl nitrate. On decomposition, this compound formed a basic carbonate which lost carbon dioxide and water at 200-300”.E x P E R I M E N T A L . Preparation of the Yellow Compound.-In a typical experiment a mixture of 60 g. of ethyl ether 60 g. of uranyl nitrate and 20-60 g. of water after being shaken until the nitrate dissolved was exposed ta bright sunlight for periods up to 24 hours. The ether was then removed by distillation at as low a temperature as possible, and the aqueous solution evaporated. On cooling there separated a yellow compound mixed with uranyl nitrate which was freed from the latter by washing with cold water in which the former was comparatively insoluble. The yield was poor and rarely exceeded 12 g. The yellow compound was found to be identical in properties with the normal hydrated oxalate of uranium, U0,C,04,2&0 (Found U 60.5 ; C,O, 22.2 ; H,O 9-7 ; C 6.1 ; H 1.2.Calc. U 604; C,O, 22.3; H20 9.1 C 6.1 ; H l-Oy&) ETHER TO OXALIC ACID IN PRESENCE OF URANYL NITRATE. 2901 Uranium was determined gravimetrically as U,O, and oxdafe volumetrically . Formation of a New Basic Omlute of Uranium-In a few of the above experiments the compound which resulted appeared different -from the normal oxalate ; it had a lighter yellow colour. It gave the u d reactions of an oxalate (Found U 68-0; C,O, 1200%). The basic oxalates which comeqond with the normal oxalates would be U( OH),,U0,C20,,2~0 and UO,( OH),,U0,C,04,2~0, depending whether the uranium in the hydroxide is quradri- or sexa-valent. The former of these contains U 68.0; C204 12.6% and the latter U 68.2; C,O, 12.6%.Either of these might be the compound analysed above. Since the compound U(OH) is stabler than UO,(OH), we are inclined to prefer the first formula. It may be written UCH40, which is identical with that of Soddy’s product. The formula of the other product so h t t e n , differs however only by a single hydrogen atom. There is no doubt that a basic oxalate is formed by the interaction of uranyl nitrate and ether in the presence of sunlight and it is probable that Soddy’s product was this oxalate. Fopmation of Uranous Eydroxide.-We find that when uranyl nitrate in solution in ether is neutralised so that a precipitate is just not formed and exposed to sunlight for periods of a few hours, there settles from solution a black or greenish-black slimy preci-pitate which accompanies the basic and normal oxalates.. It is not formed in solutions of uranyl nitrate containing free nitric acid. It resembles the product obtained by adding ammonia to a solution of a uranous.salt namely U(OH), and this composition waa con-h e d by analysis (Found U 78.0. Calc. U 77.8%). These observations are in agreement with the work of Aloy and Rodier (Bull. Soc. chim. 1920 27 101; 1922 31 246) and of Aloy and Valdiguid (ibid. 1925 37 1135) who found that in neutral solution uranium salts on exposure to sunlight in the presence of certain organic compounds yield a black or a violet precipitate the former being manous hydroxide and the latter of composition U30,,2Q0, through partial reduction of the uranyl salt.It is evident from these results that the composition of these lower oxides like that of the oxalates varies with the conditions in which they are formed. Suggested Mechanism of the Reaction.-In the absence of sunlight, none of the products described above is formed. Exposure to sunlight is therefore essential to the reactions. The oxalates formed are not oxidation products of an impurity in the ether for the most carefully purified ether gave the oxalate and addition of alcohol the most likely impurity did not increase the yield. More-over no oxalate resulted when alcohol replaced ether in the solutio 2902 OXIDATION OF ETHPI; ETHER TO OXALIC ACID ETC. of uranyl nitrate although we found atii Aloy and his co-workers did that it favours the formation of a hydroxide of uranium in neutral solution.No oxalate was obtained when other uranyl salts replaced the nitrate. Ebelman (Ann. Chim. Phys. 1842,5,198) first pointed out that solutions of the uranyl salts of strong acids were changed by sunlight in presence of an oxidisable compound acquiring a green colour which we now know to be due to uranous salts and this work has been greatly extended by Aloy and co-workers (Zoc. cit.). On their view if A be an acceptor of oxygen e.g. alcohol and uranyl nitrate the salt considered the reaction proceeds in sunlight as U02(N0,) + 2HN0 + A = U(NO,) + H,O + A 0 in presence of a sufliciency of nitric acid. If suflicient acid be not present it is to be expected that some uranous hydroxide would be formed and this is what we have found.When ether is the acceptor it is oxidised finally we find to oxalic acid. In presence of uranyl ion and free nitric acid this would be expected to form the normal oxalate as it does; in presence of insufficient acid a mixture of the normal oxalate and uranous hydroxide or a compound of these would be expected to form. The manner of oxidation of ether to oxalic acid has not been previously considered in the literature. We suggest the following. Ether is oxidised to diglycol when the uranyl is reduced to the uranous ion by sunlight. Part of the diglycol is oxidised by nitric acid to diglycollic acid and part hydrolysed to glycol which is then further oxidised by nitric acid to oxalic acid thus : / diglycollic acid. ‘ s glycol + oxalic acid. We find the latter. Ether + diglycol It is of course known that diglycol is oxidised by nitric acid partly to oxalic acid but mostly to diglycollic acid. It has not yet been possible to test this scheme by showing the presence of either diglycol or diglycollic acid. A generous grant from the Caird Fund of the British Association DR. LEE’S LABORATORY, provided the materials of this research. CHRIST CHURCH OXFORD. [Received hlovemher 23rd 1925.