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first with increasing percentage of metal, gradually slackens its rate of decrease, and more and more nearly approaches a fixed limit. On the other hand the bismuth and lead amalgams have their resistance decreasing down to a minimum and then rising to a maximum.

The initial character of the curves for these amalgams is therefore different to that of the curves of the alloys of Class 2 which have been investigated by Mathiessen.

In both amalgams and alloys points of maxima and minima occur corresponding to definite chemical combinations. The alloys of mercury with bismuth and lead, however, have this special peculiarity, that they conduct better than either of their constituents.

C. S. Conductivity of Acids and Salts in Dilute Solutions. By E. BOUTY (Compt. rend., 104, 1611-1614).-The conductivity of dilute solutions of acids and of salts other than normal salts does not follow the simple law which has been found to hold good for normal salts (Compt. rend., 102, 1097, 1372), a result similar to that obtained in the electrolysis of the same solutions. The resistance at constant temperature is, however, sensibly proportional to a factor 1+ Km, but the limit and the coefficients in the equation (loc. cit.) vary for different substances. Determinations of the conductivity of very dilute solutions of sulphuric, nitric, and hydrochloric acids shows that their molecular resistance varies with the temperature, although within somewhat narrow limits. If the resistance of sulphuric acid is taken as unity at each temperature, the resistances of the other acids in the highest possible degree of dilution are represented by the following numbers:

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When the resistance of solutions of these acids is compared with that of solutions of their normal salts, it is found that the ratio between the two quantities depends mainly on the temperature, and varies greatly at different temperatures. C. H. B.

Electric Conductivity of Compounds of Potassium and Sulphur in Solution, of Sodium Sulphide and of Boric Acid. By O. Bock (Ann. Phys. Chem. [2], 30, 631–638).-The author has measured the conductivity of mixtures of alkaline hydroxide and alkaline hydrosulphide represented by the formula 3KOH + KSH, KOH + KSH = K2S(+ H2O), KOH + зKSH, KSH and Na S. The conductivities and temperature coefficients are given in tables for many different concentrations in each case. For these the original paper must be referred to.

The conductivity of KOH, like that of NaOH, is diminished by the addition of hydrogen sulphide. Each mixture of hydroxide and hydrosulphide shows an independent maximum of conductivity for some particular strength of solution, which increases with the amount of hydrosulphide present.

When the solutions are dilute, the conductivities of KOH, KS, and

KHS are to each other nearly as 1 :: ()'. Thus each addition of an electrochemical sulphur molecule, S/2, to one of potassium (or sodium) diminishes the conductivity by one-third. Similarly, the author finds the conductivities of the pentasulphides, K2S, and Na2S,, in solution to be about one-third of that of the corresponding sulphide solutions. The conductivity of various solutions of pure boric acid is also given. This acid is one of the worst known conductors. The trace of sodium present in the commercial acid increases the conductivity threefold. Сн. В.

Nobili's Rings and Allied Electrochemical Phenomena. By A. ELSAS (Ann. Phys. Chem. [2], 30, 620-630).-The author believes, in opposition to Voigt, that Nobili's rings are mainly due to currents which traverse the electrolysed liquid nearly parallel to the metal plate. The colours obtained are not in all cases colours of thin plates; but the rings are sometimes deposits of different chemical and physical constitution. In fact, electrochemical decomposition takes place not only at the surfaces of the electrodes, but at every point throughout the liquid traversed by the current. This is proved as follows. Plaster of Paris moistened with copper sulphate solution is poured on a metal plate, and a copper wire plunged into the still soft mass with its end very close to the plate. The plaster is allowed to set firmly, and a current is passed from wire to plate. On removing the cake, four or five coloured rings are seen on its surface, corresponding rings being found on the plate. The plaster also adheres to the metal more or less firmly in different zones, and is also distorted. The central area opposite the wire is green (CuH2O, ?), and is surrounded by rings successively white, blue, white, red (Cu) and again blue. When the current is long continued, coloured deposits are also found throughout the mass of the gypsum. The colours of the rings are independent of the nature of the metal plate, when the latter does not directly act on the electrolyte.

When the anode wire is of platinum, the electrolyte becomes acid and pure copper is nowhere deposited. When it is of iron, rustcoloured rings are found in the gypsum plate, showing that transference of the ions takes place even in the solid. If the metal plate is made the anode, a blue circle appears round the cathode, surrounded by an intensely blue ring.

When a current is passed between two wires immersed in a plate of gypsum, prepared as above on a plate of glass, circular coloured rings are formed round each wire. The isochromatic lines do not correspond either with the equipotential lines or the lines of equal current-intensity. If in this experiment a metal plate is substituted for the glass, rings also appear on its surface. These appear to coincide with the equipotential lines only at some distance from the wires.

Theoretical views follow as to the distribution of potential in the last case. But the appearances cannot be explained by reference to this alone, as Guébhard imagines.

Сн. В.

Variations in the Electrical Resistance of Antimony and Cobalt in a Magnetic Field. By G. FAE (Phil. Mag. [5], 23, 540-541).—Rods of antimony when placed in the magnetic field of a Ruhmkorff electromagnet showed an increased electrical resistance, the resistance being greater across the lines of force than along them. Plates of cobalt when so placed showed a diminished resistance when their planes and the current were perpendicular to the lines of force. When placed parallel to them an increase was observed. Further results are promised. H. K. T.

Expansion of Salt Solutions. By W. W. J. NICOL (Phil. Mag. [5], 23, 385-401).-The expansion of the salt solutions is determined in dilatometers heated to constant temperatures by means of the vapour of a liquid boiling under a constant and adjustable pressure maintained by means of a water-pump and a somewhat elaborate pressure regulator. The solutions were made up to molecular strengths by weighing, placed in a vacuum, boiled for ten minutes, cooled, and the composition checked by taking the density in a Sprengel tube. It was found that the results could be expressed by the interpolation formula, V = 100,000+ t'a + t'ß where t' = (t 20). The error being within ±2 in 100,000. The results showed that the more concentrated the solutions the more nearly did the curves of volume approach a straight line, these being in every case nearer than that of water. Again the value of ẞ being less for water than for any of the solutions, it follows that the volume difference must reach a maximum at some temperature. To find this the volumes of the salt solutions were calculated by interpolation for every 5° between 20° and 100°, as compared with those of water. The following are the maxima

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55-60° about 50°

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90-95°
90°
80-85°
80°

none
80-85°

75-80°

With 8 and 10 NaCl and 3, 5, and 7 KCl the volume of the solution at 100° is less than that of water. With NaCl and KCl at 100° the stronger the solution the smaller the volume, whilst with KNO, the reverse is the case. In order to compare the results in molecular 1800+ nM.W. volumes, the author multiplies by (Abstr., 1886,

δ

763). The maxima are now found to be moved up. At high temperatures NaCl and KCl solutions expand less the more concentrated the solutions, whilst with NaNO, and KNO, this is not the case. author considers this to be due to the effect of temperature on the

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solubility of the respective salts, KNO, and NaNO, solutions becoming, so to speak, more dilute at high temperatures. H. K. T.

Tellurium. By BERTHELOT and C. FABRE (Compt. rend., 104, 1405-1408).-The different varieties of tellurium were finely powdered and dissolved in bromine and water saturated with bromine, the thermal disturbance being measured. The precipitated varieties were washed and dried in an atmosphere of nitrogen. The following mean numbers were obtained:-

Crystallised tellurium, prepared by volatilisation
in hydrogen

Tellurium precipitated by sulphurous acid..
Tellurium precipitated from alkaline tellurides by
the action of air or other oxidising agents....
Tellurium precipitated from hydrogen telluride
by oxidising agents

+66.66 Cal. +42.584,,

+66.78

+67-01

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The tellurium precipitated from hydrogen telluride and alkaline tellurides is identical with the crystalline variety, and the mean heat of solution in bromine and water is +66.776 Cal.

From these results it follows that the conversion of crystallised tellurium into the amorphous variety develops +24 192 Cal., and that tellurium, like sulphur and selenium, exists in two perfectly distinct states. Molten tellurium thrown into cold water and then treated as above gives numbers varying from 44 to 56 Cal., which indicate that it is a mixture of the crystalline and amorphous varieties.

It is worthy of note that the change from amorphous to crystalline tellurium absorbs heat, the corresponding change for selenium develops heat, whilst the similar change in the case of sulphur gives rise to no sensible thermal disturbance at the ordinary temperature, but is positive at a high temperature, and doubtless becomes negative at a low temperature.

It is also of interest that tellurium precipitated in alkaline liquids and from hydrogen telluride, is identical with the crystalline variety, whilst that precipitated by sulphurous acid constitutes a distinct modification. Similar phenomena are observed in the case of sulphur. C. H. B.

Heats of Combustion of Organic Substances. By J. THOMSEN (Ber., 20, 1758-1759).-The author quotes results obtained in the estimation of the heats of combustion of organic substances by Berthelot and Vielle by combustion with oxygen in the calorimetric bomb, and by Stohmann by combustion with potassium chlorate, and points out that the results obtained by the latter are always far lower than those obtained by the former. This he attributes to Stohmann's use of an indirect and an inaccurate method. A. J. G.

Heats of Combustion. By BERTHELOT and RECOURA (Compt. rend., 104, 1571-1574).-These determinations were made by means of the calorimetric bomb.

Glucose. Heat of combustion per gram 3·762 Cal.; per gram-mole

cule +677.2 Cal. This value is sensibly equal to the heat of combustion of lactose, and is identical with half the heat of combustion of saccharose (+677-5 Cal.). These results agree with those previously obtained by Berthelot and Veille. The heat of formation of glucose is +300·8 Cal. The union of carbon in the form of diamond (C) with water (6H2O) to form glucose would absorb -113.2 Cal., a result which explains the development of heat during alcoholic fermentation and the reserve energy associated with the carbohydrates which plays such an important part in vital processes.

Quinone.-Heat of combustion per gram 6102 Cal; per grammolecule +659.02 Cal. Heat of formation +45.2 Cal. The union of C. with 2H2O to form quinone would absorb -92.8 Cal., an absorption relatively greater than that which accompanies the formation of glucose.

Naphthalene. Heat of combustion per gram 9.6888 Cal.

Benzoic Acid.-Heat of combustion per gram 6.345 Cal.; per gram-molecule +7731 Cal. at constant volume; 772.8 Cal. at constant pressure. Heat of formation +92-2 Cal. The union of C,H, with CO2 would absorb -30 Cal.

Salicylic Acid.-Heat of combustion per gram 5:326 Cal.; per gram-molecule +734-99 Cal. at constant volume and constant pressure. This value agrees with that calculated from the heat of combustion of phenol, and the heat of transformation of salicylic acid into phenol and carbonic anhydride. C. H. B.

Heats of Combustion. By BERTHELOT and LOUGUININE (Compt. rend., 104, 1574-1577).-These results were obtained by means of a calorimetric bomb smaller than that used by Berthelot and Recoura (preceding Abstract).

Naphthalene.-Heat of combustion per gram 9.6961. The general mean of this and the previous results is +9-700 Cal. Heat of combustion per gram-molecule +1241·6 Cal. at constant volume; 1242·7 at constant pressure. Heat of formation from its elements -26.7 Cal. Phenol.-Heat of combustion 7.8105 Cal., which agrees with the previous determination by Berthelot and Vieille.

Benzoic Acid.-Heat of combustion 6.3221 Cal.

Cumic Acid.-Heat of combustion per gram 7·5533 Cal.; per grammolecule +1239-3 at constant volume, +1237-7 at constant pressure. The excess over the heat of combustion of benzoic acid is + 464-9, or +155 x 3 Cal.

Quinone.-Heat of combustion 6.00613 Cal.

Quinol.-Heat of combustion per gram 6-2295 Cal.; per gram-molecule +685.24 Cal. at constant volume; 6849 Cal. at constant pressure. Heat of formation +86·1. Heat of formation from hydrogen and quinone +40-9 Cal.

Pyrogallol.-Heat of combustion per gram 5.0262 Cal.; per grammolecule +633-3 Cal. at constant volume and constant pressure. Heat of formation +1377 Cal.

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