WORSLEY AND ROBERTSON THE PEROXIDES OF BISMUTH. 63 IX.-The Peroxides of Bismuth. By RICHARD ROBERT LE GEYT WORSLEY and PHILIP l%71LFRED ROBERTSON. THE most comprehensive and recent work on the peroxides of bismuth is by Gutbier and Bunz (Zeitsch. anorg. Chem. 1906 48, 163 295; 49 433; 50 211). These observers from their experi-ments on the oxidation of bismuth hydroxide in the presence of alkali hydroxide drew the conclusion that chemical compounds could not be isolated from the mixtures thus obtained even after subsequent treatment with nitric acid. It seemed however prob-able that continuous grinding with dilute nitric or glacial acetic acid might bring about a separation of the lower oxide of bismuth from the peroxide. Accordingly preliminary experiments were carried out in which ( a ) bismuth hydroxide precipitated in the oxidising medium and ( 6 ) ordinary bismuth trioxide were treated with ammonium persulphate in boiling dilute sodium hydroxide solution.The first product was comparatively rich in bismuth peroxide but its composition altered only little after grinding with glacial acetic acid; the product in the second case contained less peroxide but after several grindings its composition approximated to that of bismuth tetroxide. Experiments were therefore mad 64 WORSLEY AND ROBERTSON THE PEROXIDES OF BISMUTH. in this manner with different oxidising agents in the presence of sodium or potassium hydroxide of different concentrations. In dilute solutions bismuth tetroxide was the only product; in more concentrated solutions higher oxides were also formed.These products were analysed in the following manner the peroxidic oxygen was estimated ( a ) by distillation with hydrochloric acid (Bunsen’s method) ( b ) when the substance was soluble by dis-solving in hot nitric acid (D 1.2) and measuring the liberated oxygen; the peroxidic oxygen plus water was determined by heat-ing t o redness. The compounds for which analytical results are given below were free from sodium or potassium. Action of Chlorine on Bismuth Trioxide suspended in Boiling A 1 kali Hydroxide. The product of the reaction in dilute solution (5-10 per cent.) was either BkO (brown) or Bi,O,,H,O (brown). The exact conditions determining the formation of the anhydrous oxide or the hydrate could not be ascertained.In concentrated alkali hydroxide (35-40 per cent.) there was formed a mixture of Bi205,H20 (red) and Bi,0,,2H20 (yellow) from which the lower oxide could be fractionally separated by the action of hot nitric acid (D 1.4). The following values were obtained in one typical experiment for a mixture ( A ) after two grindings with glacial acetic acid; ( B ) after three grindings with glacial acetic acid; (C) after one extraction with hot nitric acid; ( D ) after two extractions with hot nitric acid: A . B. C. D. Peroxidic-0 ........................ 5.20 6-05 3.94 3-47 Peroxidic-0 + H,O ............... 10.05 10.02 9.97 10.00 The duration of each experiment was about half an hour. Bi20,,2H,0 requires 0 = 3.10 ; 0 +H,O = 10.08 per cent. Bi,O,,H,O requires 0 = 8-22 ; 0 +H,O = 9.73 per cent.According to Deichler (Zeitsch. anwg. Chem. 1899 20 lll), the product of the reaction should be a mixture of Bi,O and Bi,0,,H20 and the Bi20,,2H,0 is produced by the action of nitric acid on the latter. The colour of the substance A (orange-red), the analytical results and its behaviour with nitrio acid all indicate that it was a mixture of Bi,O,,ZH,O (yellow) and Bi205,H,0 (red). Action of Ammonium Persulphate OT Potassium Ferricyani.de on Bismuth Trioxide suspended in Boiling Alkali Hydroxide. The product of the reaction in dilute solution was either Bi,O, (brown or purplish-black) or Bi,04,H20 (brown or purplish-black) WOB8LEY AND ROBERTSON THE PEEOXIDES OF BISMUTH. 65 The experimental conditions determining the formation of these four varieties could not be ascertained.I n concentrated alkali there was formed in addition to Bi,O or Bi,O,,H,O a small amount of Bi,O (yellow) which could be fractionally separated from the lower oxide by the action of hot nitric acid (D 1 - 2 ) . Bismuth Tetroxide Bi,O,(BiO,). This was prepared by the action of chlorine ammonium per-sulphate or potassium ferricyanide on bismuth trioxide suspended in a dilute solution of boiling alkali hydroxide and the following modifications have been obtained I Bi,O (brown); 11 Bi20, (purplish-black) ; 111 Bi,O,,H,O (brown) ; IV Bi,O,,H,O (purplish-black) . The following are typical analyses for preparations which had been ground with glacial acetic acid in an agate mortar until they were completely free from bismuth trioxide and occluded alkali hydroxide : I.11. Bi,O,. Peroxidic-0 ............... 3.31 3-26 ; 3.20* ; 3.39 3.33 per cent. Loss on heating ............ 3.27 3.24 3-61 3-33 ,, 111. IV. Bi204,H20. Peroxidic-0 ............... 3.25 ; 3.07 3.13 ; 3.21 3.21 p0r cent. Peroxidic-0 + H,O.. ....... 6-88 ; 6.20 6-22 ; 6-92 6.83 ,, * Determined gasometrically. The brown and purplish-black anhydrous bismuth tetroxides appear to be physical isomerides and are both stable a t looo. The modifications with one molecule of water lose the water in a vacuum (1 mm.) over phosphoric oxide slightly darkening in colour. At looo in the steam-oven they lose half this amount : 111. IV. Loss at 100' ............... 1.70 1-74 1-89 Bi,O,,H,O requires hH,O = 1.81 per cent.A t 160° all varieties decompose with the liberation of oxygen. Bismuth tetroxide is soluble in nitric acid (D 1.2) at 70-90°, yielding its peroxidic oxygen in the gaseous form (with small quantities of ozone). It is peculiarly reactive immediately oxidising manganous salts in the presence of dilute nitric acid even in the cold. Bismuth tetroxide is very sparingly soluble in con-centrated alkali hydroxide with the formation of an unstable per-salt. Another distinct variety Bi,0,,2H20 (yellow) is formed, together with Bi,O,,H,O by the action of chlorine on bismuth VOL. cxvrr. 66 WORSLEY AND ROBERTSON THE PEROXIDES OF BISMUTH. trioxide in boiling concentrated alkali hydroxide. It may be fractionally separated from the higher oxide by treatment with boiling nitric acid (D 1-4) in which it is only sparingly soluble.The following analyses were obtained for two preparations : I. 11. Bi,O,,BH,O. Peroxidic-0 ............ 3.47 3.38 3.10 per cent. Peroxidic-0 +H,O.. .... 10.00 9.95 10.08 ,, At looo it decomposes darkening in colour with the loss of both oxygen and water. Bkmu t h Pent oxide Bi,O,. The monohydrate Bi,O,,H,O (red or brown) soluble with diffi-culty in hot concentrated nitric acid is obtained (a) mixed with Bi,04,2H,0 by the action of chlorine on bismuth trioxide in boil-ing concentrated alkali hydroxide ( b ) in small quantities mixed with Bi,04,H20 by the action of ammonium persulphate on bismuth trioxide in dilute alkali hydroxide at 40-60° when the action is allowed to continue for five to six hours.The bismuth pentoxide produced by the first method could not be separated from the admixed Bi,04,2H,0; obtained according to the second reaction it could be completely separated from the Bi,04,H20 by extraction with hot nitric acid (D 1.2). Three different samples gave the following values on analysis: Peroxidic-0 ......... 5.97 6.05 6-26 6.22 per cent. Peroxidic-O+H20. .. 9.80 - 10.16 9.73 ,, A second variety Bi,0,,H20 (brown) readily soluble in hot nitric acid (D 1.2) is obtained from commercial sodium bismuthate after repeated grinding with glacial acetic acid. The following analyses were obtained for three different preparations : Peroxidic-0 ......... 6*20* 6-19* 6-14 6.22 per cent. I. 11. 111. Bi,06,H,0. I. 11. 111. Bi,O,,H,O Peroxidic-0 + H,O... 10.00 9.91 9-96 9.73 ,, * Determined gasometrically. Anhydrous bismuth pentoxide would appear to be incapable of existence. The hydrate when left in a vacuum (1 mm.) over phosphoric oxide darkens in colour and slowly loses water and oxygen. A t looo the decomposition is more rapid; in one experi-ment the percentage of peroxidic oxygen fell from 6.2 to 1.9 in twenty days and subsequently remained constant indicating that bismuth trioxide and bismuth tetroxide had been formed in approximately equal amounts TEE ACTION OF MERCURTC CYANIDE ON METATLIC SALTS. 67 Bismuth Hexoxide Bi,0,(Bi03), Bismuth hexoxide is obtained in small quantities by the action of ammonium persulphate or potassium f erricyanide on bismuth trioxide suspended in boiling concentrated alkali hydroxide, together with bismuth tetroxide (Bi,O or Bi,04,H,0) from which it can be separated by continuous extraction with warm nitric acid (D 1.2). It may also be prepared by the oxidation of the tetroxide and subsequent treatment of the product with nitric acid. A t the ordinary temperature it loses oxygen slowly darkening in colour. This would explain the slightly low results obtained on analysis : Bismuth hexoxide is pale brown and contains no water. I. 11. Bi,O,,. PeroXidic-0.. . . . . 8.96 9.13 9.37 per aent. Loss on heating 9.00 9.1 1 9.37 ,, IMPERIAL COLLEUE OF SCIENOE AND TECHNOLOUY, SOUTH KENSMQTON. [Received November 6th 1919.