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The chemical news
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The chemical news
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Band 1.1860
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- Titelblatt Titelblatt I
- Sonstiges Advertisement III
- Ausgabe No. 1. - December 10, 1859 1
- Ausgabe No. 2. - December 17, 1859 13
- Ausgabe No. 3. - December 24, 1859 25
- Ausgabe No. 4. - December 31, 1859 37
- Ausgabe No. 5. - January 7, 1860 49
- Ausgabe No. 6. - January 14, 1860 61
- Ausgabe No. 7. - January 21, 1860 73
- Ausgabe No. 8. - January 28, 1860 85
- Ausgabe No. 9. - February 4, 1860 97
- Ausgabe No. 10. - February 11, 1860 109
- Ausgabe No. 11. - February 18, 1860 121
- Ausgabe No. 12. - February 25, 1860 133
- Ausgabe No. 13. - March 3, 1860 145
- Ausgabe No. 14. - March 10, 1860 157
- Ausgabe No. 15. - March 17, 1860 169
- Ausgabe No. 16. - March 24, 1860 181
- Ausgabe No. 17. - March 31, 1860 193
- Ausgabe No. 18. - April 7, 1860 205
- Ausgabe No. 19. - April 14, 1860 217
- Ausgabe No. 20. - April 21, 1860 229
- Ausgabe No. 21. - April 28, 1860 241
- Ausgabe No. 22. - May 5, 1860 253
- Ausgabe No. 23. - May 12, 1860 265
- Ausgabe No. 24. - May 19, 1860 277
- Ausgabe No. 25. - May 26, 1860 289
- Ausgabe No. 26. - June 2, 1860 301
- Register Index 313
- Beilage No. 1. December 10, 1859 I
- Beilage No. 2. December 17, 1859 IX
- Beilage No. 3. December 24, 1859 I
- Beilage No. 4. December 31, 1859 I
- Beilage No. 5. January 7, 1860 I
- Beilage No. 6. January 14, 1860 I
- Beilage No. 7. January 21, 1860 V
- Beilage No. 8. January 28, 1860 I
- Beilage No. 9. February 4, 1860 I
- Beilage No. 10. February 11, 1860 I
- Beilage No. 11. February 18, 1860 I
- Beilage No. 12. February 25, 1860 I
- Beilage No. 13. March 3, 1860 I
- Beilage No. 14. March 10, 1860 I
- Beilage No. 15. March 17, 1860 I
- Beilage No. 16. March 24, 1860 I
- Beilage No. 17. March 31, 1860 I
- Beilage No. 18. April 7, 1860 I
- Beilage No. 19. April 14, 1860 I
- Beilage No. 20. April 21, 1860 I
- Beilage No. 21. April 28, 1860 I
- Beilage No. 22. May 5, 1860 I
- Beilage No. 23. May 12, 1860 I
- Beilage No. 24. May 19, 1860 I
- Beilage No. 25. May 26, 1860 I
- Beilage No. 26. June 2, 1860 I
- Beilage No. 27. June 9, 1860 I
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THE CHEMICAL NEWS. Vol, I. No. 7. —January 21, i860. SCIENTIFIC AND ANALYTICAL CHEMISTRY. On Various Methods for the Estimation of Copper, by Frederick Field. '[second part, continued from p. 63.] 0. Mohr precipitates metallic copper from its neutral solution by means of metallic iron. C11O.SO3 + Fe = Fe0.S0 3 + Cu. and estimates the amoimt of iron in the protosulphate by permanganate of potash. The solution is made very slightly acid, and chloride of sodium added. Too much heat is avoided during precipitation, as basic persalts of iron are thrown down at an elevated temperature. This method, when performed with care, according to Mohr, gives accurate results. I have always met with diffi culties in its execution, as an excess of acid, however slight, necessarily gave results too high by an excessive formation of chloride of iron; and when no acid was present basic salts were formed in such a quantity as to yield an apparent loss of copper. Fleitmann precipitates the copper by metallic iron in the same manner as Mohr: washes the precipitate, and dissolves in perchloride of iron. Fe 2 Cl 3 + Cu = 2 FeCl + CuCl. The iron is determined, as before, by permanganate of potash. The results are very accurate. In both the above processes much time and labour are doubtless spent in vain. It is far easier and quite ns exact (more so, indeed, than in Mohr’s method) to weigh the precipitated copper after washing and drying, if tlio precautions already advised have been followed, than to redissolve it, and' estimate an equivalent of iron. If two equal weights of sulphate of copper, for example, are taken, dissolved in water, acidified, and precipitated by iron; in one case the copper is simply washed, dried, and weighed, and in the other it is redissolved in per chloride of iron, and the protochloride of that metal determined. Both the simple precipitation process and Fleitmann’s give equally satisfactory results; hut the former has the advantage of being more expeditious and less complicated. Mohr’s process will be seen at once to be perfectly in admissible in the assay of the great bulk of copper minerals, unless he separates the copper by a preliminary operation, as iron is invariably present. Streng’s method.—The oxide of copper is reduced to suboxide by grape sugar, a solution of starch and iodide of potassium added, and afterwards a standard solution of bichromate of potash, until a permanent blue colour is produced. 3 Cu 2 0 + Cr 2 0 6 = 6 CuO-l Cr 2 0 3 . Dr. Streng takes advantage of the fact that bichromate of potash expels iodine from hydriodic acid, and the former then gives a blue colour with starch paste, in case no reducing substance is present. Thus no perma nent blue can be formed as long as any subchloride of copper exists; but when the whole is converted into protochloride by the decomposition of the chromic acid, the blue iodide of starch remains. This method yields accurate results, but caution is required in the addition of the iodide of potassium. Diniodide of copper is excessively insoluble in hydrochloric acid unless the latter be in great excess, so that when a considerable quantity of the alkaline iodide is employed, and little hydrochloric acid is present, there is not much dichlo ride of copper in solution. The formation of the green sesquichloride of chromium also interferes disagreeably with the blue colour of the iodide of starch, rendering it difficult to tell when that compound is permanently pro duced. Dr. Streng has proved by many experiments that grape sugar in the cold has little or no reducing power upon bichromate of potash. Leval’s process consists in placing a plate of metallic copper in an ammoniacal solution of oxide of copper until the latter becomes colourless, Cu0.NH 4 0 + Cu = Cu 2 O.NH 4 0. the loss the copper has sustained corresponding to the quantity of copper originally in solution. The method is exact, but very tedious. MM. Plessy and Moreau form a protocliloride of copper as nearly neutral as possible by the addition of ammonia and the subsequent employment of hydrochloric acid, so as just to remove the blue colour and to present the well-known green of chloride of copper; and boiling this solution with a strip of metallic copper until it becomes colourless,—the loss of weight indicates the amount of metal in the chloride. CuCl + Cu = Cu 2CI. In the notice of this method in the Chemical Gazette, in one of the numbers for 1859, it is said that iron interferes in the reaction, as metallic copper in solutions of salts of iron and copper reduces the copper to its minimum whilst the iron is at its maximum of oxidation. This is probably an error of translation, as the reduc tion of persalts of iron to protosalts by copper is known to every one ; and, in fact, one or two processes quoted above depend upon its reducing action. Mr. E. O. Brown dissolves the cupreous compound in nitric acid, adds carbonate of soda, and afterwards acetic acid in excess. Iodide of potassium is then added, equal at least to six times the weight of the copper. A standard solution of hyposulphite of soda is poured into the flask from a burette until the brown colour nearly disappears. Clear starch liquid is then introduced, and a further ad dition of the hyposulphite, until the blue colour is destroyed. This process, which yields most accurate results, fails to do so in the presence of peroxide of iron, not only, as Mr. Brown remarks, on account of the deep colour of peracetate of iron, but more particularly be cause the peroxide becomes partially deoxidised by the hyposulphite, and thus the reaction is interfered with. The estimation of copper in many alloys, &c. is by this method very rapid and trustworthy. Jacquelin has proposed to determine the amount of copper by means of a comparison of the intensity of blue in its ammoniacal solution. A series of tubes are
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