FOURCROY AND THENARD, DAVY, WOLLASTON: 200.8 Fourcroy and Thenard found 8 0=100 Hg. Davy found 30 0380 Hg, giving Hg= 1266. The latter also found 134 Cl 380 Hg, which for Cl=441, gives Hg=1254. (Phil. Trans., 104, 1814, 21.) = N. G. SEFSTROEM: 202.53 (0=16); 1265.822 (0 = 100). Determined by three analyses of the oxide according to which 100 Hg=7.89, 7.9, and 7.97 O. (Berzelius' Lehrbuch, 3, 1215.) E. TURNER: 200.72 (016). Turner made a number of determinations of this atomic weight but regarded the value he adopted, 202, only as an approximation. From the oxide, prepared from nitrate, he got 200.77 and 199.97. The compound was decomposed by heat, and the products carried over silver and gold in a narrow tube. Four experiments were made on mercuric chloride which was decomposed by pure calcic oxide, and the Cl precipitated with argentic nitrate. [These analyses recalculated for the Stas' atomic weights of Ag and Cl give 202.079, 201.701, 201.815.] Turner also made two experiments on the reduction of the chloride with stannous chloride, the Hg being collected, dried and weighed. [These experiments recalculated give 199.423 and 199.289.] The mercuric chloride was purified by recrystallization. Weighings reduced to vacuum. (Phil. Trans., 123, 1833, 535.) ERDMANN AND MARCHAND: 200.14 (0 = 16); 1250.6 (0 = 100). Determined from the mean of four experiments on the reduction of the oxide in a current of carbon di-oxide. Copper, carbon (from sugar) oxide, and carbon, were introduced in successive layers in a combustion tube. Dry carbon di-oxide was passed through and the mercuric oxide heated. The metal was collected in a receiver to which a tube filled with gold foil was appended. The metal was perfectly clean. Moisture was removed by a stream of dry air after distillation. The oxide was purified by heating it to incipient decomposition the metallic fumes being removed by a current of dry air. It was tested before being analysed. The extreme difference in the results was 0.8 for 0 = 100. All weighings in vacuo. (Erdmann's Journ. für Prak. Chem., 31, 1844, 392.) E. MILLON: 199.94 (0 = 16); 1249.63 (O = (0 = 100). Millon made two experiments by heating mercuric chloride with calcic oxide in a current of hydrogen and condensing the metal. The experiments gave 73.87 and 73.82 per cent. mercury. If Cl 442.64, the value follows. The chloride was dissolved in ether and sublimed. It was perfectly soluble in ether and alcohol, and was well crystallized. (Paris Comptes Rend., 20, 1845, 1291.) = L. SVANBERG: 200 (0 = 16); 1250 (0 = 100). Svanberg made three experiments by the same method employed by Millon. The mean result was 1248.47; extreme difference, 0.94; but Svanberg shows that there was probably loss, and that the larger the quantity of chloride employed the higher the result. He regards Erdmann and Marchand's result as most probable, but in need of confirmation. Cl=443.28. (Erdmann's Journ. für Prak. Chem., 45, 1843, 468; Kongl. Vet. Akad. Handl., 1845, 135.) MOLYBDENUM. Regnault determined the specific heat of molybdenum. It answers to an atomic weight of about 96. (Gmelin-Kraut, 1. c.) J. J. BERZELIUS: 95.36 (0 = 16); 596.1 (0 = 100). One hundred parts of anhydrous plumbic nitrate, dissolved and precipitated with neutral ammonium molybdate, gave 110.68 parts plumbic molybdate. If Pb = 1294.645, N=87.53, the value follows. Berzelius expresses himself dissatisfied with the accuracy of the determination. (Poggend. Ann., 8, 1826, 23; and Lehrbuch, 3, 1208.) SVANBERG AND STRUVE: 92.13 (016); 575.829 (0 = 100). After trying various methods without getting accordant results, these chemists made ten experiments on the sul = phide by roasting it first in a current of moist, and then of dry air. Three experiments were excluded as imperfect. The remainder gave a mean of 89.7523 molybdic acid from 100 sulphide; extreme difference, 0.22. The value follows for S 200. Objections have been made (Liebig's Ann., 68, 211) that the difference in weight between the acid and the sulphate is too small for the purpose of the determination, and that the different analyses give very different atomic weights. The sulphide was prepared by melting together molybdic acid, sulphur, and caustic potash, and leaching the product with water and chlorhydric acid. The sulphide was dried in a current of hydrogen. The molybdic acid was dissolved in ammonia to prove the absence of sulphide. (Erdmann's Journ. für Prak. Chem., 44, 1848, 315.) N. J. BERLIN: 91.96 (016); 574.75 (O = 100). Determined by four analyses of the double mono-sesquimolybdate of ammonium by heating gently with nitric acid in a platinum crucible until only molybdic acid was left. Extreme difference, 3.32 for O=100; N=175; H=12.5. The preparation of the salt is not given. (Erdmann's Journ. für Prak. Chem., 49, 1850, 446.) J. DUMAS: 96 (0 = 16). Dumas made five experiments on the reduction of molybdic acid (prepared from the natural sulphide) by means of hydrogen. The reduction was begun at a low temperature in a glass tube, and completed in an unglazed porcelain tube in a reverberatory furnace, where it was kept till several hours heating produced no further alteration in weight. The molybdenum did not assume a metallic appearance. The number is the mean; extreme difference, 0.8 for 0 = 16. (Annal. de Chim. et de Phys., (3,) 55, 1859, 142.) M. DELAFONTAINE : 92 (0 = 16); 575 (O = 100). This chemist made many experiments in various ways without being able to reach constant results, and only remarks that his experiments indicate Svanberg and Struve's value as the best. (Erdmann's Journ. für Prak. Chem., 95, 1865, 137; Bibl. Univ., Arch. des Sciences, 23, 1865.) H. DEBRAY: 95.94 (0 = 16). Debray made three experiments on the reduction of molybdic acid. The acid was first converted into the red oxide in platinum, and at a low temperature, and the small portion of the acid volatilized during this operation was caught and determined. The reduction was completed in a porcelain tube at a white heat. Debray gives his results at 48.03; 48.04; and 47.84. [The analytical data, recalculated, give 95.30; 95.55; 95.73; perhaps on account of misprints. Reduction to vacuum would still further reduce the numbers.] The acid was purified by sublimation in platinum, conversion into ammonium salt, and regeneration by heat. In two experiments ammoniacal solution of molybdic acid was evaporated in the dark with excess of argentic nitrate, the argentic molybdate dissolved out and the excess of silver determined. Debray found 5.510 acid acid=7.657 silver, and 7.236 acid=10.847 silver. Hence he calculates M48 and 47.98. [A little calculation shows that the first data are misprinted. They should read 5.11 acid = 7.657 silver. The corrected data give for Ag=107.93; M 96.06 and 95.99. The mean of the recalculated analyses is 95.73.] (Paris Comptes Rend., 66, 1868, 732.) = L. MEYER: 96.10 (0 = 16). Calculated from three analyses of the dichloride, two analyses of the tetrachloride, and two analyses of the pentachloride, made by Leichte and Kempe in Meyer's laboratory. The dichloride was analyzed by heating in a current of hydrogen sulphide, and subsequently in a current of hydrogen. Molybdenum disulphide is the residue. The HCl formed was caught in ammonium hydrate and precipitated by argentic nitrate, after the hydrogen sulphide had been driven off by boiling in a flask provided with a condensing drip-tube. The tetra and pentachloride were decomposed with nitric acid, excess of ammonium hydrate was added, and molybdenum trisulphide precipitated with ammonium sulphide. A weighed portion of the dry precipitate was converted into disulphide by heating in a current of hydrogen. The chlorine of the higher chlorides was determined in the filtrate after precipitation of the trisulphide. By comparing the amount of chloride analyzed with the amount of argentic chloride obtained, Meyer finds in mean M = 95.92; extreme difference, 1.87 for O= = 15.96. By comparing the amount of disulphide with that of argentic chloride, M = 95.75; extreme difference, 1.35. By comparing the amount of chloride analyzed with the amount of disulphide obtained for one analysis of tetrachloride and two analyses of pentachloride, he gets M 95.94; extreme difference, 2.15. The general mean is M 95.86; extreme = = = difference, 2.15. Ag Ag=107.66; S-31.98; Cl = 35.37; O=15.96. The specific gravities of the chlorides not having been determined, the weighings are not reduced to vacuum. The pentachloride was prepared from M by heating it in a current of Cl entirely free from air. The metal had been freed from oxide by heating in an atmosphere of HCl. By moderate heating of the pentachloride in dry H, and by distilling pentachloride over the product in dry carbon di-oxide, the trichloride is obtained. The trichloride heated in carbon di-oxide is decomposed into tetrachloride and di-chloride, which latter must be purified with warm dilute nitric acid. (Liebig's Ann., 169, 1874, 360, 344.) NICKEL. Regnault has determined the specific heat of nickel. It corresponds to an atomic weight of about 59. (GmelinKraut, l. c.) E. ROTHOFF: 59.09 (0 = 16); 369.333 (0 = 100). Rothoff converted 188 parts of oxide into chloride, a neutral solution of which gave 718.2 parts argentic chloride. If Cl=221.64, Ag 1349.66, the value follows. (Berzelius' Lehrbuch, 3, 1221.) P. BERTHIER. = Lassaigne having announced the atomic weight of nickel at 500, (Schweigger's Jahrbuch, 9, 108,) Berthier re-examined the subject and found Rothoff's number confirmed. (Berzelius' Jahresbericht, 5, 1825, 148; Annal. de Chim. et de Phys., 25, 1824, 148.) ERDMANN AND MARCHAND: 58.2 (O= 16); 365.9 (O = 100).. Determined" with all precaution" by the reduction of the oxide with hydrogen. The results varied from 29.1 to 29.3, but Erdmann has reason to believe the smaller number the more accurate. (Erdmann's Journ. für Prak. Chem., 55, 1852, 202.) |