Electrochemical Equivalent Research Articles

Erratum

Page 339, line 25 : for “ indicating a decomposition of 1 gramme electrochemical equivalent in 30,000 years,” read “ indicating the separation, by decomposition, of 1 gramme of Hydrogen or of its electrochemical equivalent in 3,000,000 years.”

The electrochemical equivalent of silver

A preliminary account of the recent redetermination of the electrochemical equivalent of silver by Van Dijk and Kunst has been given in the “Proc. Roy. Acad., Amsterdam, Jan. 21, 1904,” and in the “Ann. Phys. Vol. 14, p. 569, 1904.” Van Dijk has now published the interesting details of the research.The tangent galvanometer method was employed, a method which requires the accurate knowledge of the intensity of the horizontal component of the Earth's magnetic field. This was determined by means of a bifilar magnetometer, with wires 232 cms. long and 12.4 cms. apart. Great pains were taken to eliminate all possible errors, and the difficulties encountered clue to local magnetic influences in the instruments are fully described.

Letter to editor: Mr. Watson's comparison at Kew Observatory

With reference to the note (Vol. 7, p. 99) on the abstract of Mr. Watson's paper in the “R. S. Proceedings,” and to the foot‐note attached thereto, I would point out that, subsequent to the publication of the abstract, Mr. Watson found that, “owing to a mistake in the corrections applied to the weights used in the silver depositions, the numbers . . . which appeared in the ‘Proceedings of the Royal Society’ (Vol. 69, p. 1) require correction.” This correction (see “Phil. Trans.,” Vol. 198 A, pp. 454‐6) raises Mr. Watson's values dependent on the weights in question by some 6 γ or 7 γ, bringing his mean value for H, expressed in international units, into almost exact agreement with the corresponding mean from the Kew magnetometer. Mr. Watson himself (1. c., pp. 461–2) considers .0011183 a more probable value for the electrochemical equivalent of silver than the value .001118 accepted at present, and if the revised value he approves were accepted, it would increase the apparent difference between the results from the coil and magnetometer. It is hardly necessary to point out that until the electro‐chemical equivalent of silver is really known to 5 significant figures—instead of to 4, as at present—any comparison of coils and magnetometers based on it can not lead to absolute final results.

Notes

With reference to the note (Vol. 7, p. 99) on the abstract of Mr. Watson's paper in the “R. S. Proceedings,” and to the foot‐note attached thereto, I would point out that, subsequent to the publication of the abstract, Mr. Watson found that, “owing to a mistake in the corrections applied to the weights used in the silver depositions, the numbers . . . which appeared in the ‘Proceedings of the Royal Society’ (Vol. 69, p. 1) require correction.” This correction (see “Phil. Trans.,” Vol. 198 A, pp. 454‐6) raises Mr. Watson's values dependent on the weights in question by some 6 γ or 7 γ, bringing his mean value for H, expressed in international units, into almost exact agreement with the corresponding mean from the Kew magnetometer. Mr. Watson himself (1. c., pp. 461–2) considers .0011183 a more probable value for the electrochemical equivalent of silver than the value .001118 accepted at present, and if the revised value he approves were accepted, it would increase the apparent difference between the results from the coil and magnetometer. It is hardly necessary to point out that until the electro‐chemical equivalent of silver is really known to 5 significant figures—instead of to 4, as at present—any comparison of coils and magnetometers based on it can not lead to absolute final results.

Abstracts and reviews

With reference to the note (Vol. 7, p. 99) on the abstract of Mr. Watson's paper in the “R. S. Proceedings,” and to the foot‐note attached thereto, I would point out that, subsequent to the publication of the abstract, Mr. Watson found that, “owing to a mistake in the corrections applied to the weights used in the silver depositions, the numbers which appeared in the ‘Proceedings of the Royal Society’ (Vol. 69, p. 1) require correction.” This correction (see “Phil. Trans.,” Vol. 198 A, pp. 454‐6) raises Mr. Watson's values dependent on the weights in question by some 6 γ or 7 γ, bringing his mean value for H, expressed in international units, into almost exact agreement with the corresponding mean from the Kew magnetometer. Mr. Watson himself (1. c., pp. 461–2) considers .0011183 a more probable value for the electrochemical equivalent of silver than the value .001118 accepted at present, and if the revised value he approves were accepted, it would increase the apparent difference between the results from the coil and magnetometer. It is hardly necessary to point out that until the electro‐chemical equivalent of silver is really known to 5 significant figures—instead of to 4, as at present—any comparison of coils and magnetometers based on it can not lead to absolute final results.

The Electrochemical Equivalents of Copper and Silver

The Electrochemical Equivalents of Copper and Silver

A New Determination of the Electrochemical Equivalent of Silver

A New Determination of the Electrochemical Equivalent of Silver

On the use of cupric nitrate in the voltameter, and the electro-chemical equivalent of copper

"On the use of cupric nitrate in the voltameter, and the electro-chemical equivalent of copper." The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science, 36(221), p. 384

Scientific Serials

American Journal of Science.—August.—We notice the following papers:—The use of cupric nitrate in the voltameter and the electro-chemical equivalent of copper, by Frederick.E. Beach. Copper nitrate solution of density 1˙53 possesses certain advantages over the sulphate in voltameters. It is best to add one drop of saturated NH4Cl solution. The dependence of the amount of copper deposited upon the current density does not appear until a density of 0˙25 ampèeres per sq. cm. of electrode: is reached, and then it is counteracted by adding more NH4C1. With the nitrate, the weight of copper deposited is practically independent of the temperature between 10° and 35°. The solution may be used a number of times. The equivalent of copper as determined from the nitrate voltameter agrees to foar figures with that calculated from the best chemical determinations. But it is essential that the solution should be pure, and especially free from traces of nitrite.—On Mackintoshite, a new thorium and uranium mineral, by Wm. Earl Hidden; with analysis by W. F. Hillebrand. This is the original mineral of which thorogummite, discovered in 1891, is the alteration product. It is an opaque black mineral of hardness 5˙5, and resembles zircon and thorite in form. It differs from thorogummite by the further oxidation of the uranium and the assumption of one molecule of water. It contains three molecules of silica, one of urania, three of thoria, and three of water:—On the reduction of nitric acid by ferrous salts, by Charlotte F.Roberts. The volume of nitric oxide disengaged, swept along, by carbon dioxide and collected over caustic soda, was measured for the estimation of nitrates. The best results were obtained by passing the gas through KI solution before collecting,and estimating from the total volume of gas collected. Nitric oxide, being slightly soluble in caustic soda solution, must not be left long in contact with it. When the reaction takes place at high temperatures, some higher oxides of nitrogen may be formed, but this is corrected by the KI solution.—Concerning the structure of caoutchouc, by Hermann F. Lueders. Caoutchouc has no definite structure per se, and all apparent structure is only the result of the conditions under which its coagulation from the latex and subsequent solidification take place.

The use of cupric nitrate in the voltameter, and the electro-chemical equivalent of copper

The use of cupric nitrate in the voltameter, and the electro-chemical equivalent of copper

XV. On the Clark cell as a standard of electromotive force

The experiments recorded in the following paper were undertaken with the object of testing various points in the manufacture and use of the Clark cell as a standard of electromotive force, specially with a view of investigating the most simple method of setting up a number of such cells which should have, within certain limits, a definite electromotive force, and of determining the limits within which, it is safe to say, that the E. M. F. of such a cell will lie. We have also determined afresh the relation between the E. M. F. of a Clark cell and the electrochemical equivalent of silver. The experiments have been conducted in the main on the lines of those described in Lord Rayleigh’s papers “ On the Electrochemical Equivalent of Silver and on the Absolute Electromotive Force of Clark Cells” (‘ Phil. Trans.,’ Part II., 1884), and “ On the Clark Cell as a Standard of Electromotive Force ” (‘ Phil. Trans.,’ Part II., 1885).

II. On the Clark cell as a standard of electromotive force

The paper consists of two parts:— In Part I an account is given of experiments on the absolute electromotive force of a Clark cell. This was determined in the manner described by Lord Rayleigh (‘Phil. Trans.,’ 1884) in terms of a known resistance and the electrochemical equivalent of silver.

Scientific Serials

Annalen der Physik und Chemie, No. 6, June.—R. Emden, on the vapour-pressures of saline solutions. Criticism of prior results, and fresh experiments conducted according to the method of Konowalow. Babo's law, that the vapour-tension of saline solutions is always proportional to that of pure water at the same temperature, is shown to be true between 20° C. and 95° C.—Max Planck, on the principle of increase of entropy. Application of this principle in the study of dissociation of gases.—C. R. Schulze, on the amount of water of crystallization held in various salts. Proves the existence of a new form of sulphate of magnesia having density 1.8981, containing six molecules of water, and therefore differing from Mitscherlich's salt of same composition of density 1.6151.—W. Voigt, on the theory of light for absorbing isotropic media. A development of the theory propounded by the author three years ago.—C. L. Weber, on the galvanic conductivity of amalgams. The amalgams examined were of tin, bismuth, lead, cadmium. Addition of tin increases conductivity of mercury; bismuth increases it until 10 per cent, of bismuth has been added, after which further addition decreases the conductivity; lead shows a maximum at about 25 per cent.; cadmium produces a steady increase in conductivity.—Adolf Koepsel, determination of magnetic moments and absolute strength of currents by means of the balance. The method is due to R. von Helmholtz, and is independent of the earth's magnetic field or its variations. The author has made by this method a new determination of the electro-chemical equivalent of silver, which he gives as 0.011740 ± 0.0000022 in C.G.S. measure. Lord Rayleigh's value was 0.011794.—Walter König, magnetic researches on crystals. A very careful research on magnetic susceptibility of quartz and calc-spar in magnetic fields of various degrees of intensity. The two principal permeabilities in calc-spar possess a constant difference in fields of various strengths up to 3000 C.G. S.; for quartz, the difference diminishes as the field is strengthened, and is less than that of calc-spar.—R. Clausius, reply to some remarks of Lorberg upon dynamo-electric machines.—A. Foeppl, electricity as an elastic fluid. A speculative paper: the author thinks the existence of the Hall effect a criterion of his theory.—K. Wesondonck, on the absence of polar difference in spark-potential.—G. Meyer, note on the index of refraction of ice; the value for sodium light is 1.3133.—E. Ketteler, on the dispersion of rock-salt. The author thinks he has established the law that the absorbing power of substances for heat-rays is proportional to the negative coefficient of the term in λ2 in the formula which he uses in place of Cauchy's for the law of dispersion.—W. Voigt, reply to Wernicke's remarks on elliptic polarization.—F. Braun, on the diminution of the compressibility of solutions of sal-ammoniac with increase in temperature.—A. Overbeck, on the signification of the absolute system of measurement.

IV. On the clark cell as a standard of electromotive force

This paper, supplementary to that “On the Electrochemical Equivalent of Silver, and on the Absolute Electromotive Force of Clark Cells,” gives the further history of the cells there spoken of, and discusses the relative advantages of various modes of preparation. The greatest errors arise from the liquid failing to be saturated with zinc sulphate, in which case the electromotive force is too high. The opposite error of super -saturation is met with in certain cases, especially when the cells have been heated during or after charging. Experiments are detailed describing how cells originally supersaturated have been corrected, and how in others the electromotive force has been reduced by the occurrence of supersaturation consequent on heating.

XVII. On the electro-chemical equivalent of silver, and on the absolute electromotive force of clark cells

§ 1. In former communications to the Royal Society we have investigated the absolute unit of electrical resistance, and have expressed it in terms of the B. A. unit and of a column of mercury at 0° of known dimensions. The complete solution of the problem of absolute electrical measurement involves, however, a second determination, similar in kind, but quite independent of the first. In addition to resistance, we require to know some other electrical quantity, such as current or electromotive force. So far as we are aware, all the methods employed for this purpose define, in the first instance, an electrical current; but as a current cannot, like a resistance, be embodied in any material standard for future use, the result of the measurement must be recorded in terms of some effect. Thus, several observers have determined the quantity of silver deposited, or the quantity of water decomposed, by the passage of a known current for a known time. In this case the definition relates not so much to electric current as to electric quantity. A more direct definition of the unit current, and one which may perhaps be of practical service for the measurement of strong currents of 50 ampères or more, would be in terms of the rotation of the plane of polarisation of sodium light, which traverses a long column of bisulphide of carbon enveloped by the current a given number of times. Other observers have expressed their results as a measurement of the electromotive force of a standard galvanic cell. In this case it is necessary to assume a knowledge of resistances. The known current in passing a known resistance gives rise to a known electromotive force, which is compared with that of the cell.

X. On the electro-chemical equivalent of silver, and on the absolute electromotive force of clark cells

The paper contains a record of a long series of experiments, extending over nearly two years. The measurement of the electric currents is direct, not depending upon a knowledge of the force of terrestrial magnetism. Three horizontal coils are traversed in succession by the electric current. Of these two of large diameter are fixed, and at a distance apart equal to the radius of either. Symmetrically between them a smaller coil is suspended in the balance. When the current passes, the suspended coil is pressed down, or lifted up, according to the connexions, and the observations relate to the double force called into operation when the direction of the current in the fixed coils is reversed . In a paper read before the British Association at Southampton it was shown that this construction presents special advantages, and in particular that the calculation of the result does not require an accurate knowledge of the radii of the coils, but only of the ratio of the radii of the small and large coils. In this way one of the principal difficulties, the measurement of the small coil, is evaded.

Societies and Academies

LONDON Royal Society, March 27.—“On the Electro-chemical Equivalent of Silver, and on the Absolute Electromotive Force of Clark Cells.” By Lord Rayleigh, D.C.L., F.R.S.

II. On the electro-chemical equivalent of silver, and on the absolute electromotive force of clark cells

The investigations upon this subject which have been carried on by Mrs. Sidgwick and myself during the last year and a half, though not yet quite finished, are so far advanced that no doubt remains as to the general character of the results; and as these results have application in the daily work of practical electricians, it is thought desirable to communicate them without further delay. The currents are measured by balancing the attraction and repulsion of coaxal coils against known weights, as described before the British Association in 1882, a method which has fully answered the favourable expectations then expressed. To what was said on that occasion it will be sufficient for the present to add that the readings are taken by reversal of the current in the fixed coils, and the difference of weights thus found (about 1 gram) represents the double force of attraction, free from errors depending upon the connections of the suspended coil, and other sources of disturbance.

On the Electrolysis of Sulphate of Copper 1

THE immediate object of this research was to examine various conditions connected with the transmission of electric currents through solutions of salts of copper, and to ascertain the influence of those conditions on the electro-chemical equivalent of copper, also to observe for any signs of conduction of electric currents by such liquids without electrolysis. In many of the experiments some difficulty was experienced in ascertaining the exact loss of weight of the anode, in consequence of finely-divided copper falling from it. The powder which fell off, exposing as it did a large surface to the liquid, was somewhat oxidised, and also in acid solutions freely dissolved, and its true weight, and therefore the exact loss of the anode could not be found.

Scientific Serials

Scientific Serials