Personal- und Vorlesungsverzeichnisse der Technischen Hochschule und Universität Stuttgart: Technischen Hochschule Stuttgart. Personal- und Vorlesungsverzeichnis für das Studienjahr 1936/37

Technischen Hochschule Stuttgart. Personal- und Vorlesungsverzeichnis für das Studienjahr 1936/37 (1936)

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Persistenter Identifier:: 1530689129952

Titel:: Personal- und Vorlesungsverzeichnisse der Technischen Hochschule und Universität Stuttgart

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Persistenter Identifier:: 1530689129952_1936_1

Titel:: Technischen Hochschule Stuttgart. Personal- und Vorlesungsverzeichnis für das Studienjahr 1936/37

Jahrgang/Band:: 1936

Verleger/Verlag:: Buchdruckerei Karl Scharr Vaihingen a. d. F. Stuttgart

Erscheinungsjahr:: 1936/37

Sprache:: deutsch

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Titel:: G. Vorlesungen und Uebungen

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Titel:: Abteilung für Wissenschaften

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Titel:: II. Naturwissenschaften

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j Gumuica News} Combinations of Aurin with Mineral Acids. 25 + copper are diluted to 1 litre. 1 c.c. = o'orox3} grm. THE CHEMICAL NEWS. Mgr) . This process, from its extreme simplicity, will commend itself for approximate comparative examinations. The ferrocyanide of copper, if present’in larger quanti- ties than those indicated above, hides too much the blue colour of the Prussian blue, and must be separated before applying the ferrous sulphate. Moreover, in concentrated solutions, the precipitate of ferricyanide of copper contains more cyanogen per atom of copper than the formula CusFe,Cyi, requires. In dilute solutions, however, the amount of copper solution required is such as to corres pond sufficiently close with the formula above stated ; and considering that not one of the many other compounds contained in soda-lyes interferes with this process of estimating the cyanogen, it will rival in accuracy any other volumetric process devised for this purpose. If it is apprehended that the solution under examination contains cyanide of sodium beside ferrocyanides, it must irst be boiled with a small quantity of ferrous oxide, pro- duced by adding a little ferrous sulphate. The solution 's then oxidised, acidified, and is ready for testing. The sulphocyanide is present in traces only. It can approximately be estimated by acidifying the solution under examination, adding some chloride of zinc to pre- cipitate ferrocyanide of zinc. The solution is then filtered, and the filtrate coloured by means of ferric chloride. In a second vessel an equal quantity of ferric chloride, diluted to the bulk of the solution under examination, is coloured by means of a solution of sulphocyanide of potassium of known strength, until the tint of both solutions is alike. The amount of sulphocyanide thus consumed is in some iegree a measure of the sulphocyanide contained in the ye, but this is usually so smali that its estimation is of no practical utility. Laboratory of Messrs, Gaskell, Deacon, and Co., Widnes, January, 1870. THE cyanogen compounds which occur in soda-lyes are the following :— Sodium ferrocyanide, Sodium sulphocyanide, Sodium cyanate. Though in crude soda (black-ash) the cyanogen is con- tained as cyanides, the soda-lye obtained therefrom con. tains no cyanides. During the lixiviation the cyanides are transformed into ferrocyanides, and all the vat-liquors I have yet investigated contained more iron in solution than the cvanogen would account for. If, however, sodium cyanide is present at all it is readily converte¢ into ferrocyanide by boiling the liquid with freshly pre. cipitated protoxide of iron. The most important of the cyanogen compounds to the manufa&urer is the ferrocyanide, since this salt brings into the solution a sufficient amount of iron to colour the finished produé slightly brown. The sulphocyanide and the cyanate are pra&ically of no importance, as they yield colourless products of decom- position during the further treatment of the soda. The chief problem to the chemists of alkali works, consists, therefore, in the rapid estimation of the ferrocyanides. The following method will be found exceedingly rapid, and sufficiently accurate for solutions containing not more than 2 grms. of sodium cyanide per litre. . When soluble ferricyanides are mixed with salts of copper a yellow precipitate of ferricyanide of copper is formed. If a proto-salt of iron is added afterwards a blue precipitate will be formed so long as any ferricyanide exists still in solution. As soon, however, as all the ferricyanide has been precipitated, the addition of a ferrous salt produces no longer a blue colour, but reads upon the ferricyanide of copper, reducing it to ferrocyanide of similar composition to that obtained on adding to an excess of ferrocyanide of potassium a copper solution gradually. The reaction is represented by the following equation :— Cu;Fe,Cyiz+2HCI+2FeCl; =CusgH, Fe, Cy1z-+ Fe Cle. This readion suggests an indire estimation of the cyano- gen compounds by measuring the amount of protoxide of iron which can be transformed into peroxide. It is not, however, this which forms the principle of the method now to be described, and which makes use of the above re- action simply as indicator. } roo c.c. of the strong soda-lye are oxidised by means of chlorine, hypochlorite of soda, or, simpler, bleaching- powder solution, until the whole of the sulphides, &c., are converted into sulphates, and the ferrocyanide into ferri- cyanide ; the solution, after being acidified and freed as much as possible from excess of chlorine by warming and agitating, is ready for titrating. On a porcelain slab sprinkle a few drops of a dilute solution of ferrous sulphate (x part of ferrous sulphate to 100 parts of water). Add now to the solution to be analysed a twentieth normal copper solution from a burette until a drop of the solution, on being brought in conta& with a drop of ferrous sulphate solution, no longer gives a blue colour, but yields the pure purple colour of cupric ferrocyanide. The copper solution is prepared by dis. solving pure metallic copper .in as. little nitric acid as possible, and diluting with distilled water. (3°17 grms. of Mv —— ON THE COMBINATIONS OF AURIN WITH MINERAL ACIDS.* By R.S.DALE, B.A, and C. SCHORLEMMER, F.R.S. In our last communication} we stated that by the aéion of acetyl chloride on aurin we obtained a colourless crys- talline compound, which we intended to examine more closely, We have since found that this body is identical with a compound which Gribe and Caro} obtained by the dire& union of aurin and acetic anhydride and having the formula CoH r,034+C,HeO3. We also mentioned that the purification of this sub- stance was found to be beset with several difficulties. The cause of this was found out after some trouble, but at the same time we were rewarded by the discovery of a series of remarkable bodies, consisting of combinations of aurin with mineral acids. These salts, as we may call them, are beautiful bodies, crystallising exceedingly well, and although some of them are decomposed by water, they are very stable in dry air. To their discovery we were led by the following observa- tions. On heating aurin with glacial acetic acid and acetyl chloride, the crystals lose at once their steel-blue lustre ind assume a pale red colour. To obtain the compound ‘hus formed in a pure state, acetyl chloride was added to 1 saturated solution of aurin in acetic acid. The liquid assumed at once a much lighter colour, and soon pale red needle-shaped crystals having a-diamond lustre separated put. On re-crystallising these repeatedly from alcohol * Read before the Manchester Literary and Philosophical Society December 10, 1878. t Proc. Lit. and Phil. Soc., 1878, 141, and CHEM, NEWS, vol. XxXViil., ) 34. t Ber, Detitsch. Chem. Gesell. xi., 1, 122.

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