Page:Encyclopædia Britannica, Ninth Edition, v. 18.djvu/102

O X E O X E starch or molasses ; but this method, though not by any means obsolete, is almost superseded by a new process which we owe to Mr Dale of Manchester. Mr Dale s process is founded upon the old observation of Gay-Lussac s that cellulose, by fusion with caustic potash, is oxidized into oxalate with evolution of (impure) hydrogen. In Mr Dale s works (at Warrington) sawdust and wood-shavings do service as cellulose, while a mixed caustic alkali lye of 1 3-i to 1*35 specific gravity, containing IK HO for every SNaHO, serves as a reagent. Unmixed caustic soda gives no or little oxalate. The wood -shavings are soaked in a quantity of lye equal to 30 to 40 per cent, of their weight of dry alkali, and the mixture is evaporated down on iron plates at about 200 C. with constant agita tion, until it is converted into a homogeneous brown mass completely soluble in water. This mass (which is as yet very poor in oxalate) is then dried up fully at a somewhat lower temperature, and thus converted into a crude oxalate equivalent to 28 to 30 per cent, of its weight of oxalic- acid crystals. Messrs Roberts, Dale, & Co. have come, latterly, to substitute for the iron plates an iron pipe passing slantingly through a heated chamber and provided inside with a revolving screw, which draws in the mixture of wood and alkali below, and conveys it along at such a rate that it comes out above as finished product. The crude oxalate is lixiviated with cold water, when the bulk of the oxalic acid remains as soda salt, while the rest of the alkali passes into solution as, substantially, carbonate. The oxalate, after having been washed with the least suffi cient quantity of water, is boiled with a dilute milk of lime and thus converted into a precipitate of oxalate of lime, while caustic soda passes in to solution, which is added to the liquors produced in the separation of the oxalate of ] soda from the surplus alkali. The oxalate of lime is j washed and then decomposed by boiling it with three times i the calculated amount of dilute sulphuric acid, the sulphate I of lime filtered off, and the solution evaporated to crystal lization. The yield as oxalic acid crystals amounts to 50 to 60 per cent, of the weight of the wood-shavings. The united alkali-liquors are causticized with lime, and thus (apart from the unavoidable losses) the originally employed caustic alkali is recovered in its entirety. Commercial (oxalic) acid is contaminated chiefly with sulphuric acid and alkali, of which the latter cannot be removed by recrystallization from water, but, according to Stolba, easily and exhaustively by recrystallization from 10 to 15 per cent, hydrochloric acid. Crystallized oxalic acid forms colourless needles of tlie composi tion C 2 4 H 2 + 2H Z 0. It melts at 98 C., and when kept at about this temperature readily loses its crystal -water, but at 110 the dry acid C 2 4 H 2 already begins to volatilize. The latter sublimes most readily at 165 C. , without previous fusion, in needles. At higher temperatures it breaks up, more or less completely, into C0 2 + formic acid, CH 2 2 (or CO-f II 2 0). The crystallized acid dissolves in 10 5 parts of water of 14 5, also in alcohol. The solution readily neutralizes basic hydrates and carbonates ; in the case of the alkalies and alkaline earths, the point of neutrality to litmus corresponds to the normal salt, i.e., to the ratio CO 2 1I : HHO, where R=K, Na, (NH 4 ), ^Ba, &c. The normal salt C0 2 R com bines with 1C0 2 H into" binoxalate, " and, in the case of 11 = K or NH 4 , also with 3C0 2 H into " quadroxalate." Alkaline oxalates are soluble in water the soda aiid ammonia salts rather sparingly; of the rest of oxalates, as far as they are normal salts, the majority are insoluble or difficultly soluble in water, and therefore most con veniently produced, by double decomposition, as precipitates. Potash Salts. The normal salt, C 2 4 K 2 -f H 2 0, is soluble in 3 parts of water of 16 C. The binoxalate (salt of sorrel) is generally an hydrous, but occasionally C a 4 KH + ,jH,,0, the latter soluble in 26 2 parts of water of 8 C. The elsewhere extinct industry of manufacturing this salt from sorrel-juice survives in the Black Forest. It is used habitually for removing ink and rust-stains from linen, though oxalic ;ieid is better and cheaper. The quadroxalate, C 4 4 KH + C,0 4 II 2 + 2H L ,0, soluble in 20 parts of water at 20 C., is often sold as salt of sorrel. Soda Salts. The normal salt, C.,O 4 Xa.,, gene: ally forms small imperfect crystals, soluble in 31 - 6 parts of water of 13 C. Tim acid salt, C 2 4 NaII + H.,O, is soluble in 67 6 parts of water at 10 C. Ammonium Salts. The normal salt, C 2 4 (NH 4 ). + H 2 0, found native in guano, crystallizes in needles, and is soluble in 237 parts of water of 15" C. It is much used in the laboratory as a most delicate precipitant for lime suits. The binoxalate, C.,0 4 (NH 4 )H + H 2 0, dissolves in 16 parts of water of ll o. There is a quadroxalate, Other Salts. The normal lime salt, as obtained by precipitation of lime salts with alkaline oxalates or oxalic acid, and found in plant cells, is C,0 4 C a + 3ILO ; but 2H 2 are easily lost below 110 ; the remaining 1ILO is expelled only above 200 C. Ferrous oxalate, CO 4 Fe + 2H 2 0, obtainable by precipitation of ferrous sulphate with oxalic acid, is a yellow crystalline powder. "When heated it breaks up into C0 2 and finely divided metallic iron, which latter at once burns into red ferric oxide of a state ol aggregation which fits it pre-eminently for the polishing of optical glasses. Ferric oxalate dissolves in oxalic acid, the solution, when exposed to the light, giving off CO., with precipitation of ferrous oxalate. Draper recommends it for measuring the chemical in tensity of light. Industrially oxalic acid chiefly serves the calico printers as a discharge for certain colours, which, unlike the otherwise equivalent mineral acids, does not attack the tissue. Minor quantities are used, as solution, for cleaning metallic surfaces. It has been recommended for the metallurgic precipitation of NICKEL (q. v.). Analysis. Solid metallic oxalates, when heated, are decomposed without noteworthy elimination of carbon. When heated with oil of vitriol they give olf the components of the anhydride C 2 3 as carbonic oxide and carbonic acid gases, without blackening. Oxalate solutions are precipitated by chloride of calcium ; the precipitate (C 2 4 Ca . rH 2 0) is insoluble in water, ammonia, ammonia salts, and acetic (though soluble in hydrochloric) acid. Even a mixture of free oxalic acid and gypsum solution deposits oxalate of lime. Oxalic acid is readily oxidized into carbonic acid by the conjoint action of dilute sulphuric acid and binoxide of manganese or permanganate of potash. In the latter case this re action, even with small quantities, becomes visible by the discharge of the intensely violet colour of the reagent ; the change, however, is slow at first; it becomes more and more rapid as the MnSO 4 formed increases, and consequently goes on promptly from the first, if ready made MnS0 4 be added along with the reagent. The permanganate test is readily translatable into a titrimetric method for the determination of oxalic acid in solutions. (V. I). ) OXENSTIERNA, AXEL, COUNT OF (1583-1654), Swedish statesman, was born at FaniJ in Upland on the 16th of June 1583. He studied theology at Rostock, Wittenberg, and Jena; and in 1602, having spent some time in visiting German courts, he returned to Sweden to take the oath of allegiance to Charles IX., whose service- he entered. In 1606 he was sent as ambassador to the court of Mecklenburg, and in 1609 he became a member of the Swedish senate. When Gustavus Adolphus succeeded to the throne, in 1611, Oxenstierna was appointed chancellor, and in 1613 he was plenipotentiary in the negotiations for the conclusion of peace between Sweden and Denmark. In 1614 he went with the king to Livonia, and helped to bring about the cessation of hostilities between Sweden and Russia. After the inter vention of Gustavus in the Thirty Years War, Oxenstierna was made governor-general of all the districts in Prussia which had been overrun by the Swedes ; and, when the Imperialists were preparing to besiege Stralsund, lie- negotiated with the duke of Pomerania for the substitution of Swedish for Danish troops in the town, going subse quently to Denmark to obtain the sanction of the Danish king. While Gustavus pushed on to Franconia and Bavaria, Oxenstierna was entrusted with the supreme direction of affairs, both political and military, in the Rhine country, and he took up his headquarters at Mainz. In 1632, when Gustavus fell at the battle of Lu tzen, the responsibility for the maintenance of the Protestant cause fell chiefly upon Oxenstierna ; and in one of the greatest crises in the history of the world he displayed splendid courage, discretion, and resource. At a congress held in Heilbronn he was appointed director of the evangelical confederation, and in this capacity he went