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General and Physical Chemistry.

Degree of Oxidation of Chromium and Manganese in Fluorescent Compounds. By L. DE BOISBAUDRAN (Compt. rend., 105, 1228-1233).-This paper contains details of the results obtained by calcining, in air or in hydrogen, mixtures of pure alumina with chromic oxide; of gallium oxide and chromic oxide; of calcium oxide and chromic oxide; of magnesium oxide and chromic oxide; of alumina with small quantities of potassium and manganese oxides; and of calcium and manganese oxides.

Too large a proportion of chromium reduces and may even destroy the fluorescence. In some cases, calcination in hydrogen reduces, in others it intensifies the fluorescence, but no general conclusions are drawn as to the influence of the degree of oxidation on the pheC. H. B.

nomenon.

Rotatory Dispersion. By L. GRIMBERT (J. Pharm. [5], 16, 295— 300; 345-350).-The author employed Laurent's polarimeter and monochromatic light. To obtain rays near to C, a layer 1 cm. thick of the following solution was used:-Carmine No. 40 0-25 gram, ammonia 20 c.c., water to make up to 100 c.c. With white light, this solution gives a spectrum reduced to a very narrow band coinciding with the C line. On taking the rotative power of an active substance in this light and also in the sodium light, two different values are obtained, [a] and [a]c. The ratio [a]/[a]e gives the dispersive power. Usually tubes of 200 mm. length were employed; sometimes 100 mm. tubes were used, as, for example, when the deviation was over 20°

Saccharose. Both water and alcohol were employed as solvents. The rotative power varies neither with the concentration nor with the solvent: [] +66·45°; [a]c = 52·85°; and [a]D/[a]c = 1·257.

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Lactose. It is well known that the rotative power of lactose diminishes rapidly when first dissolved in the cold. The rotative power does not vary with the concentration. It is [a] = + 52:37 and [a]c = +41.58°. The ratio between the rotative power when first dissolved to that when it becomes stationary is as 8:5. The dispersive power is [a]p/[a]c = 1.259, and is constant during the time the rotative power is passing to the minimum. It does not vary with the concentration of the solution.

Maltose. When dissolved in the cold, the rotative power of maltose increases to a maximum. Its dispersive power is 1.262, and is constant during the time the rotative power is changing.

Glucose acts like lactose. The ratio between the initial and final rotative powers is as 2:1. The dispersive power is 1.258, and is constant whilst the rotative power is passing to the minimum.

Morphine Hydrochloride. -Solutions of different degrees of concentration confirmed the value given by Hesse, [a]D=100:67°-1·14 C.

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The dispersive power [a]/[a]c = 1.284, and does not vary with the concentration.

Codeine. In absolute alcohol, [a]p: =-134.24°, and in chloroform -114.82°, but the dispersive power only varies slightly and is on the average 1.268.

Brucine.-Anhydrous brucine, dissolved in absolute alcohol and in chloroform, gave values for [a]p confirming those obtained by Oudemans. The dispersive power does not vary with the nature of the solvent, and is = 1.357, the highest hitherto observed.

Quinine. The hydrate, dissolved in absolute alcohol, and in chloroform; the basic hydrochloride dissolved in water; and the normal sulphate dissolved in water, and in 90° alcohol, all give the same dispersive power of 1313, the variation in the solvent and in the acid combined with the base producing no change in this respect.

Cinchonine. The basic sulphate was observed when dissolved in water, absolute alcohol, and chloroform. Although the nature of the solvent has considerable effect on the rotative power of the salt, the dispersive power remains constant and equal to η268.

Strychnine.-Two samples of different character were recrystallised from alcohol, and dissolved both in 80° alcohol and in chloroform. Notwithstanding considerable differences in the rotative power of the two samples in both solvents, the dispersive power was constant and equal to 1·313.

Camphor. This substance was recrystallised from alcohol and fused. It was dissolved in alcohol of various strengths, in chloroform, and in dry ether. The rotative power varies with the nature of the solvent; its dispersive power is sensibly constant. In alcoholic solution, the rotative power increases with concentration of the alcohol, In dry ether, the rotative power does not vary with the concentration of the solution. In chloroform, as well as in alcohol, the dispersive power remains constant, notwithstanding that the rotative power increases with the concentration.

Cholesterin. This was observed in ether and chloroform. Its dispersive power averages 1323. It does not vary, like the rotative power, with the nature of the solvent.

Essence of Térébenthine.-A lævorotatory sample gave—

[a] = 30·46, [a]c=

-

28.57, and [a]/[a] = 1.241.

The results obtained with the foregoing substances show that the dispersive power remains constant whatever be the concentration of the solution; that the dispersive power of those substances whose rotative power varies with the temperature, remains constant all through that variation; that for the same substance it scarcely varies with the nature of the solvent; that each substance has its own proper dispersive power which seems to bear no relation to the chemical constitution of the substance, although it may be noted that the sugars have all the same value. J. T.

Distribution of Electromotive Force in the Cells of Batteries. By J. MIESLER (Monatsh., 8, 626-631).—The author has extended the work of Moser (this vol., p. 209) to the batteries of Grove,

Bunsen, Grenet, Smee, Lalande, and Leclanché. In every case, the total electromotive force of the battery under examination was found to be equal to the sum of the electromotive forces between the different parts of the cell. G. T. M.

Electrochemical Studies. By W. OSTWALD (Zeit. physikal. Chem., 1, 74-86 and 97-109).-From his former experiments (J. pr. Chem., 1884-1886), the author has drawn the conclusion that the molecular conductivity increases for monobasic acids with increasing dilution, tending to a maximum value which it was thought would prove to be the same for all acids. On careful repetition of these experiments, the latter view is found to be incorrect, as the maxima observed for a dilution of 1024 litres differ for 15 different acids by as much as 12 per cent. That this difference does not affect the proportionality between the maximum conductivity and the rate of chemical action of these acids is proved by experiment, the latter being in fact proportional to the relative observed maximum conductivity. A difficulty, however, obviously arises in determining the value of this maximum for feeble acids of low conductivity.

To overcome this, Kohlrausch's law that the conductivity of a neutral salt may be represented as a sum of two constants, one of which depends on the nature of the acid and the other on that of the base, is resorted to. It is shown by the determination of the conductivities of a number of sodium salts of acids of known conductivity that a constant difference exists between the two. The same holds good for lithium and potassium salts, which also differ in conductivity from the sodium salts by a constant fixed quantity. The molecular conductivities of different salts having the same base, differ very largely amongst themselves, and altogether contradict the opinion of Arrhenius and Bouty that the molecular conductivities of dilute salt solutions are the same. The numbers prove, however, that it is possible to represent the conductivity of an acid by that of one of its salts, plus some constant. The determination of these constants is reserved for a future paper.

Another interesting result is that there is an almost constant increase in the molecular conductivity of the sodium salts of the monobasic acids, with an increase in the dilution of from 32 to 1024 litres, varying between 10 and 13 units. The poorer conductors give the smaller value, so that the increase appears to depend partly on the conductivity. For bibasic acids it has about double the above value, and is nearly three times as great for tribasic. Polyvalent bases act similarly to polyvalent acids although not quite so regularly. It would seem, in fact, that if m is the molecular conductivity, and v the dilution, dm/dv is of the form n1 × 3 × const., where n is the valency of the acid, and no that of the base. According to this mode of testing, dithionic acid appears to be truly bibasic. H. C.

Pyrometer. By J. MENSCHING and V. MEYER (Zeit. physikal. Chem., 1, 145-158).-The advantage of the instrument presently to be described is that it affords a quick as well as an exact measurement of temperature. The principle of the method is to determine

the temperature from the measurement of the volumes of gas contained in the instrument at the temperature of the laboratory and at the higher temperature that is required. Part of the instrument is at a low temperature, but error from this cause is obviated by means of a compensator.

The instrument consists of a vapour-density vessel, a platinum cylinder 200 mm. high and 36 mm. in diameter. To the middle of one end of the cylinder is connected a platinum tube 350 mm. long and 4 mm. in diameter. Close by the side of this tube runs a platinum capillary tube with very thick walls, which passes through the circular end of the vapour-density vessel and goes down to within 3 mm. of the bottom. The end of the capillary tube is bent round through a right angle. The compensator is composed of a platinum tube connected at one extremity with a capillary tube, so that it is of exactly the same shape and size as the part of the instrument outside the cylinder. The instrument was heated by Perrot's gas-oven, by means of which a temperature of about 1500° can be produced.

Incandescent platinum, as Deville and Troost have shown, is permeable by hydrogen but not by air. The platinum cylinder was therefore surrounded by a Berlin porcelain tube which is impermeable to all gases.

In making an experiment, the platinum cylinder was filled with nitrogen by an india-rubber tube attached to the capillary tube, and communicating with a series of drying tubes connected with a gasometer. The quantities of gas contained in the whole instrument and the compensator at the higher temperature T were measured, and the difference reduced to volume at temperature 0° and normal pressure. Then V being a similar quantity for the temperature of the laboratory, T is given by—

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when a, y are the coefficients of cubical expansion of platinum and nitrogen. C. S.

Specific Heat of Tellurium. By C. FABRE (Compt. rend., 105, 1249-1251).-Tellurium was precipitated by means of sulphurous acid, washed with water saturated with nitrogen, and dried in a current of nitrogen. The mean of three determinations of the specific heat is 0.05252. The same tellurium was volatilised in a current of sulphurous anhydride, and was thus obtained as a black sublimate with a crystalline fracture, different in appearance from the product obtained by distillation in hydrogen. Determinations of the specific heat gave

0.05182.

Crystallised tellurium was prepared by the decomposition of alkaline tellurides, washed with water saturated with nitrogen, distilled in a current of hydrogen, fused, and allowed to cool slowly. It had a crystalline fracture. Two determinations of the specific heat gave as the mean 0.048315.

From these results, it follows that the various forms of tellurium have sensibly the same specific heats at temperatures near 100°.

Possibly differences may appear at higher temperatures, and especially near the point of transformation of amorphous tellurium into the crystalline variety. C. H. B.

Constancy in the Heat produced by the Reaction of certain Salts on each other. By S. U. PICKERING (Chem. News, 57, 75—77). -The author shows that the constancy in the heat evolved in the reaction of silver nitrate on metallic chlorides in solution, observed by Richards (Chem. News, 57, 16), is an inevitable consequence of the heat of neutralisation of hydrochloric and nitric acids being independent of the nature of the alkali, the number 16165 cal. being merely the heat of precipitation of silver chloride. Similarly, the heat measured by Fay on adding barium chloride to sulphates is the heat of precipitation of barium sulphate, 5580 cal. In this case, however, it is constant only when dyad metals are concerned, since it is only with these that the difference between the heat of neutralisation of the hydrate with sulphuric and hydrochloric acids is a constant quantity. The quantities determined by Fay have already been determined by Thomsen.

S. U. P.

Heat Equivalents of Benzoyl Compounds. By F. STOHMANN, P. RODATZ, and W. HERZBERG (J. pr. Chem. [2], 36, 353—370).—The authors, continuing their previous work (Abstr., 1887, 878), have determined the heat of combustion (in free oxygen) of the following benzoyl-compounds :

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Comparing the differences of the heat equivalents of the benzoates, salicylates, and parahydroxybenzoates, the authors calculate the heat of combustion for salicylic acid to be 723600 cal., that of parahydroxybenzoic acid 715839 cal. Thus, whilst the substitution of a hydrogen in benzoic acid to form salicylic acid decreases the heatvalue 46833 cal., a similar substitution to form the para-acid decreases it 54628. The latter number is very close to that found in the formation of phenols from benzene, and it therefore appears that the

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