E. PELIGOT: 52.48 (0 = 16); 328 (0 = 100).

Peligot reached this value by a careful carbon determination of chromous acetate, produced by precipitating a dilute solution of chromium protochloride with sodium acetate, C=75. Peligot does not regard the experiment as definitive, the salt possessing but little stability. (Annal. de Chimie et de Physique, (3,) 12, 1844, 527.)

N. J. BERLIN: 52.54 (016); 328.39 (0 = 100). Five experiments were made on the decomposition of argentic chromate with chlorhydric acid and alcohol. The silver chloride was washed in the flask in which it was precipitated, treated with aqua regia, melted and weighed without removal. The decanted fluid and the wash-water were evaporated to dryness with excess of ammonia, treated with water and the chromium oxide filtered off, heated to redness and weighed. [Nothing is said of the recovery of any argentic chloride that might have been removed by the decantation.] The value taken is calculated from the comparison of the amounts of argentic chloride and of chromium oxide obtained, Ag=1349.66; Cl=443.28. The extreme difference is 1, for O 100. The argentic chromate was prepared by adding nitrate to a solution of potassic chromate. (Erdmann's Journ. für Prak. Chem., 38, 1846, 145.)

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V. A. JACQUELIN: 50.08 (0 = 16); 313 (O = 100). By washing and purifying violet chromium chloride, Jacquelain obtained a substance which he took to be the pure chloride and which was more soluble than the unpurified salt. He analysed it by melting with soda, and arrived at the above number. (Liebig's Annal., 64, 1847, 275; Revue Scient., 14, 198.)

A. MOBERG: 53.563 (0 = 16); 334.769 (0 = 100). Moberg made twelve experiments on the decomposition of chromium salts by heat. In two cases the sulphate dried at a low red heat was decomposed by strong ignition in a platinum crucible; the results being, 335.65 and 335.29 for chromium. Ten experiments were made on the decomposition of ammonium-chromium-alum which had been dried in a pulverized state for a long time. These determinations gave from 333.965 to 335.739. The value taken is the mean. The alum employed was prepared from pure material, and was repeatedly recrystallized. S= 200; N = 87.5. (Erdmann's Journ. für Prak. Chem., 43, 1848, 115.)

J. LEFORT: 52.97 (0 = 16).

Determined by fourteen experiments on the precipitation of barium with sulphuric acid from a nitric acid solution of barium chromate. The barium chromate was prepared by precipitating potassium chromate with barium nitrate and drying the precipitate at 250°. [If these analyses are calculated for barium = 137 and S 32, they give 100 barium S32, chromate 60.244 barium oxide, extreme difference, 0.26, and the atomic weight as above. Lefort seems to have taken Ba=136.72. Berlin points out the correction which I have verified.] (Erdmann's Journ. für Prak. Chem., 51, 1850, 261; Journ. de Pharm. et de Chim., 18, 27.)

R. WILDENSTEIN: 53.485 (0 = 16).

Determined by thirty-two experiments on the precipitation of barium chloride, desiccated at a red heat, by pure, neutral potassic chromate. The mean of these analyses gave 100 barium chromate 81.70 barium chloride; extreme difference 0.35. Wildenstein calculates 334.48 without giving the assumption for chlorine. [If Cl = 35.457; Ba=137, the value follows.] (Erdmann's Journ. für Prak. Chem., 59, 1853, 28.)

F. KESSLER: 52.3 (0 = 16).

Kessler reached this value by comparing the oxidizing action of potassic chromate with that of potassic chlorate on arsenious acid. Six experiments were made on the oxidizing power of the chromate and twelve on that of the chlorate by a method of titration. By combining the maximum of one with the minimum of the other series, Kessler finds the atomic weight of chromium between 25.93 and 26.40; in mean 26.15, K being = 39.12 and Cl=35.45. Confirmatory experiments were made on the oxidation of ferrous chloride in the same way. These gave a mean of 26.1. (Poggend. Annal., 113, 1861, 137; 95, 1855, 208.)

M. SIEWART: 52.094 (O = 16).

Determined from the amount of chlorine in sublimed violet chromium chloride. Siewart criticises Kessler's determination and deduces from the latter's data a value 25.02. (Kopp's Jahresbericht, 14, 1861, 240; Halle, Zeitschr. für die Gesammt. Naturwis., 17, 530.)

Kessler points out that the number 25.02 is a misprint in the Jahresbericht, and that Siewart's paper ascribes to him the value 26.02. (Poggend. Ann., 117, 1862, 352.)

COBALT.

The atomic heat of cobalt as determined by Regnault is 6.27 if the atomic weight is assumed at 58.8. (GmelinKraut, l. c.)

E. ROTHOFF: 58.98 (0 = 16); 368.65 (O = 100). 269.2 parts of cobalt oxide converted into neutral cobaltous chloride and precipitated with argentic nitrate gave 1029.9 argentic chloride, according to Berzelius' report. (Poggend. Annal., 8, 1826, 185.) Berzelius recalculates this analysis for Cl=221.64 and Ag=1349.66, and gets the value taken. (Berzelius' Lehrbuch, 3, 1220.)

R. SCHNEIDER: 60.006 (016); 375.04 (0 = 100). Determined from four analyses of the oxalate. The carbon was determined as in organic analysis; the metal by heating a known weight of the salt first in a current of air, then in one of oxygen, and by reduction of the oxide in hydrogen. The mean of the four analyses gave cobalt at 30.003, with an extreme difference of 0.026 for C = 6. oxalate was prepared by converting the chemically pure cobalt of commerce into roseo-cobaltic chloride, from which the metal was again reduced, then dissolved in chlorhydric acid and carbonate precipitated, which was digested with oxalic acid. (Poggend. Annal., 101, 1857, 398.)

The

Marignac objects to this determination that the oxalate, being insoluble, may very likely have retained portions of the carbonate which could not be removed by washing. (Bibl. Univ., Arch. des Sciences, (2,) 1, 1858, 372.)

Schneider answers that he obtained nearly identical results from lots prepared at different times, and that he believes that he has convinced himself that the oxalate contained no carbonate. (Poggend. Annal., 107, 1859, 610.)

Gibbs, reporting Schneider's determination, remarks: "Very numerous and carefully made analyses of the ammonium-cobalt bases, executed in my laboratory, indicate 29.5 as the true equivalent of cobalt." (Silliman's Amer. Journ., (2,) 25, 1858, 438.)

C. MARIGNAC: about 59 (0 = 16).

Five experiments were made on the decomposition of cobalt sulphate by heat. This salt can be readily dried without decomposition, and the acid is completely driven off by heat, but the resulting protoxide contains a slight

excess of oxygen. In order to remove this excess it was melted under a known weight of an acid silicate of lead. The results for cobalt varied from 29.32 to 29.38. The sulphate was purified by recrystallization. Marignac also experimented on the chloride. The weight of this salt varies greatly with the moisture of the atmosphere when crystallized, and attempts to desiccate it usually result in the formation of some insoluble compound. Three analyses of chloride appearing to contain one molecule of water, and dried at 100°, performed by titration with silver solution, gave cobalt at 29.42 to 29.51. Five experiments were made in the same way on chloride either melted in a current of chlorine or of chlorhydric acid gas, or calcined with ammonium chloride. These determinations gave from 29.36 to 29.42. (Bibl. Univ., Arch. des Sciences, (2,) 1, 1858, 374.) [Marignac, in another investigation in the same volume, takes Ag 108; Cl = 35.5.]

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J. DUMAS: 59 (0 = 16).

Determined by five experiments on the titration of cobalt chloride with silver. The mean result for cobalt was 29.542; extreme difference 0.09; Ag=108; Cl = 35.5. The chloride was prepared by dissolving pure cobalt in aqua regia, evaporating in the presence of excess of chlorhydric acid and heating to redness in a current of chlorhydric acid gas. In two of the determinations cobalt from a different lot, which had been heated in a vacuum was employed. (Annal. de Chimie et de Physique, (3,) 55, 1859, 148.)

W. J. RUSSELL: 58.74 (0 = 16).

Determined by fifteen experiments on the reduction of cobalt oxide in hydrogen. The value is the mean; the extreme difference is 0.19. To obtain pure cobalt oxide Claudet's salt was prepared, purified by recrystallization, etc., reduced in hydrogen, the metal dissolved in nitric acid and the resulting salt decomposed by heating in a stream of carbon di-oxide. (Chem. Soc. Journ., (2,) I, 1863, 57.)

Schneider considers that no sufficient precautions were taken to exclude air in these experiments, and that higher oxides were formed. (Poggend. Annal., 130, 1867, 310.)

E. VON SOMMARUGA: 60 (016).

Determined by seven experiments on the reduction of purpureocobaltic chloride in a current of hydrogen. The mean of the experiments is 29.965; four of them give a

mean 29.996. The extreme difference is 0.093. The salt was prepared by solution of the carbonate in chlorhydric acid, addition of ammonia in excess, exposure to the air, washing of the precipitate with acidulated, then with pure water and drying at 110°. A special examination showed it free from other metals. Sommaruga took Cl = 35.5; N14. (Erdmann's Journ. für Prak. Chem., 100, 1867, 113; Sitz.-Bericht der k. k. Akad., 1866.)

C. WINKLER: 59 (0 = 16).

This value is derived from the mean of five experiments on the precipitation of gold from a solution of neutral crystallized chloride of gold and sodium. The metallic cobalt employed was prepared by the reduction of purpureocobaltic chloride. The latter was made from oxide, and was purified by recrystallization. Gold was assumed at 196. The mean of the results was 29.496; extreme difference, 0.071. (Fresenius' Zeitschr. für Anal. Chem., 6, 1867, 22.)

P. WELESKY: 58.98 (0 = 16).

Determined from the analysis of cobalti-cyanides, performed by drying the salt at 100°, and heating_to redness, first in a current of oxygen then of hydrogen. Four experiments with phenylammonium-cobalti-cyanide gave cobalt at from 29.38 to 29.59. Two experiments with ammoniumcobalti-cyanide gave from 29.46 to 29.55. Mean, 29.48; extreme difference, 0.21. A single experiment by Winkler's method gave 29.42. (Berlin, Bericht der Chem. Ges., 2, 1869, 592.)

W. J. RUSSEL: 58.76 (016).

Determined by the amount of hydrogen set free by the solution of cobalt in hydrochloric acid. The value is the mean of 2 (or 4?) trials. The cobalt employed was that reduced by Russel in his former experiments on the same atomic weight. (Chem. News, 20, 1869, 20.)

R. H. LEE: 59.10 (016).

Determined by analysis of cobalti-cyanide salts. They were decomposed in a crucible by heating from above. The carbon separated was burned off in air and then in oxygen, and the metallic oxide reduced in hydrogen. Six experiments on the strychnine salt gave a mean of 59.05. Six experiments on the brucine salt gave 59.15. Six experi