Page images
PDF
EPUB

relative tension = 0·06-0.07: CaN2O + 3H2O, relative tension = 0·10-0·11; after the loss of 1 mol. H2O, this fell to 004. The salt obtained by dissolving the latter in a fourth molecular proportion of water had a relative tension = 027-0·36; after 2 mols. H2O had been removed, the tension fell to 0·08-0·07, and reached 0.04 before the last traces of water were removed. The author regards this variation in the tension required to separate the different proportions of the water from the solution as affording good evidence of the existence of a molecular compound in the liquid. With SrN2O6 + 4H2O, the relative tension at 12:4° was 0.61; ZnN2O。 + 6H2O, relative tension 0.18 at 12.1°, after the loss of 2H2O this fell to 0.025, and became imperceptible when a salt containing 3 mols. H2O was left. BaH2O2+ 8H2O lost 1 mol. H2O with a relative tension = 0.88-0.92, 5 more mols. H2O were lost when it fell to 0·18-0-22, and a diminution to 0.10 to 0.12 accompanied the separation of a seventh mol. H2O; 1 mol. H2O remaining combined with the salt. SrH2O2+8H2O lost 1 mol. H2O with a relative tension = 0.73 at 17.6°, and a further 6 mols. H2O with a relative tension = 0.27 at 18.5°, 1 mol. H2O remaining combined with the hydroxide.

W. P. W.

Dissociation of Copper Sulphate. By W. MÜLLER-ERZBACH (Ber., 19, 2877-2879).-In this paper, it is pointed out that H. Lescœur, working with a different method and at higher temperatures, has arrived at results (this vol., p. 100) which agree exactly with those previously obtained by the author (Abstr., 1886, 10). Lescœur, in his criticisms on the author's earlier experiments (Abstr., 1884, 952), has overlooked these more recently published experiments on the dissociation of copper sulphate. W. P. W.

The Relation between the Efflorescence and Deliquescence of Salts and the Maximum Vapour-tensions of their Saturated Solutions. By H. LESCEUR (Compt. rend., 103, 1260—1263).—The presence of a few tenths of a per cent. of water over and above that which is actually combined with the salt, is sufficient to give the maximum vapour-tension of its saturated solution. In order that a salt may be deliquescent, the maximum vapour-tension of its saturated solution must be lower than that of the aqueous vapour in the atmosphere. The following table gives the vapour-tensions of the saturated solutions, and may be termed the scale of deliquescence at 20°:

[merged small][merged small][merged small][merged small][ocr errors][ocr errors][merged small][merged small][merged small][ocr errors][ocr errors][merged small][merged small][merged small][merged small][ocr errors][ocr errors][merged small][merged small][ocr errors][merged small][merged small][ocr errors][merged small][merged small][ocr errors][merged small][merged small][ocr errors][merged small][ocr errors][merged small][ocr errors][merged small][ocr errors][merged small][ocr errors]

On the other hand, if the vapour-tension of a hydrated salt is greater than that of the aqueous vapour in the air, the salt will be efflorescent. The following table furnishes a scale of efflorescence at 20°:

[merged small][ocr errors][ocr errors][ocr errors][ocr errors][merged small][merged small][merged small][merged small][merged small][merged small][merged small][ocr errors][merged small][merged small][ocr errors][merged small][ocr errors][merged small][ocr errors][merged small][ocr errors][merged small][ocr errors][merged small][ocr errors][merged small][merged small][ocr errors][merged small][ocr errors][merged small][merged small][ocr errors][merged small][merged small]

Density of Weak Aqueous Solutions of Certain Salts. By J. G. MCGREGOR (Chem. News, 55, 3-6).-Experiments have been made to decide:-1. Whether or not there are solutions of salts, given volumes of which are less than the volumes of the water they contain. 2. How the density of very weak solutions varies with their strength. Anhydrous copper sulphate has already been shown. to form weak solutions exhibiting the first property. Experiments with zinc sulphate, magnesium sulphate, and calcium chloride now show that these salts do not behave in this manner, but that the solutions they form are always of greater volume than the water they contain. The strength of the solutions examined, varied in the case of zinc sulphate from 0186 to 2:895 per cent. of the salt; of magnesium sulphate from 0·191 to 1·132; of calcium chloride from 0·191 to 1.320 per cent. With regard to the density of the solutions: with the zinc and magnesium salt, the increase in density is nearly in direct proportion to the percentage of salt in solution, whereas with calcium. chloride the rate of increase of density with concentration diminishes as the percentage of salt in solution increases. The mode of experimenting is fully described and the results are tabulated. D. A. L.

Cohesion and Submersion Figures. By C. TOMLINSON (Chem. News, 55, 1-2).—Referring to a paper by Ackroyd on this subject (Abstr., 1886, 971), the author recalls the work of Rogers and his own work in the same direction. In 1864, he published papers on "Submersion Figures " produced by a large variety of liquids, and diagrams were given illustrating the formation and structure of these liquid "rolling rings," and also of aërial "rolling rings." Reference is also made to other work on the same subject, to the modes of exhibiting vortex rings at the lecture table, and to the author's researches

on the action of nuclei and porous bodies in liberating vapour from boiling liquids.

D. A. L.

Weight of Drops and their Relation to the Constants of Capillarity and the Capillary Meniscus Angle. By J. TRAUBE (J. pr. Chem. [2], 34, 515-538; compare this vol., p. 101).-From the results obtained with water and with solutions of alcohol of different strengths, the author concludes that the weight of drops and their capillary constants decrease with the increasing curvature of the surface of formation of the drops; this decrease does not, however, begin before a certain degree of curvature, which is different for different liquids. The decrease of the weight of drops in the case of different liquids is not proportional to the increase of curvature, but appears to be the greater the smaller the capillary constants of the liquid. He also finds that the edge-angle of the meniscus of drops of different liquids is equal or proportional to the meniscus angle of the same liquid in capillary tubes.

Ꭲ,

The author also made a series of determinations with solutions of alcohols and acids of different strengths, observing in each case the time which was necessary for the formation of a drop from a capillary tube and also the time necessary for the formation of a drop plus the curved surface of its meniscus; by working out the proportion between these, he found that the ratio of the time of formation between the curved surface of the drop-meniscus and the drop increases with the increasing radius of the tube; and that the dropmeniscus in general increases in proportion to the drop with increasing concentration of the solution; that is, with decreasing cohesion. The Tw difference in the quotient decreases with increasing concentration (T1 = time of formation of the drop-meniscus, T = that of the drop); therefore, curves constructed with the concentrations (as abscissa) and these quotients are concave. With compounds of an homologous series, and equal concentration, the drop-meniscus increases with the molecular weight of the dissolved substance. The determination of the size of the drop-meniscus was made in order to see if any conclusion regarding the meniscus angle could be drawn from their respective sizes. The results showed that-1. The volume of the drop-meniscus and the top meniscus angle, which the tangential planes, formed by the last particles of the curved surface of the dropmeniscus, form with the horizontal tube wall, decreases with increasing concentration of the solution, like the meniscus angle in capillary tubes. 2. For substances of an homologous series, in solutions of equal strength, the volume of the drop-meniscus decreases with the increasing molecular weight of the dissolved substance, as do also the top edge of the angle of the drop-meniscus, and the meniscus in capillary tubes.

In conclusion, the author considers that Laplace's hypothesis, according to which the meniscus angle for wetting liquids is equal to , cannot be maintained in view of the results obtained by the direct measurement of the capillary meniscus at different temperatures, and by the measurement of drops; moreover, one of the most important

theories of capillarity can only be maintained if the finiteness of the meniscus angle is accepted.

Wilhelmy's important law of the constancy of the meniscus angle cannot be accepted in its universality, since the size of this angle appears to depend on the temperature of the liquid and the curvature of the walls of the tube. Moreover, the meniscus angle, which the surface of a drop forms with a horizontal glass surface, is not, as Quincke supposes, equal to that which is enclosed by the meniscus surface in tubes with a vertical partition. The one is perhaps the complement of the other. G. H. M. Volatilisation of Dissolved Substances during the Evaporation of the Solvent. By P. M. DELACHARLONNY (Compt. rend., 103, 1128-1129).—Concentrated solutions of sulphuric acid, sodium hydroxide, sodium carbonate, and ferric sulphate were heated at 6570° in vessels closed by inverted funnels. In a few hours, the fact that some of the dissolved substance had been carried off in the vapour of the solvent was easily recognised by means of suitable test-papers which had been placed in the apex of each funnel. Even at the ordinary temperature, the papers had distinctly changed after four or five days.

Acid solutions of alum and of ferrous sulphate at the ordinary temperature gave similar results.

There is no evidence of the actual carrying off of solid particles; the colour of the test-papers was uniform, and not in streaks or patches. C. H. B.

The Periodic Law. By W. SPRING (Ber., 19, 3092-3093).—A question of priority with regard to Emerson Reynolds's illustration of this law (Chem. News, 54, 1).

Inorganic Chemistry.

Formation of Active Oxygen in the Atmosphere, and its Connection with the Electric Phenomena of the Air and the Production of Storms. By C. WURSTER (Ber., 19, 3208-3217). — Observations made by the author lead him to conclude that ozone is formed in the air by the action of sunlight on clouds. When clouds are continually formed from above, they all become laden with ozone, whilst when they form from below only the upper layer will contain much ozone. In the former case, the accumulation of ozone causes the clouds to become strongly negatively electric, and so gives rise to thunderstorms. N. H. M.

Formation of Active Oxygen in Paper. By C. WURSTER (Ber., 19, 3217—3218).-The yellow and brown colour acquired by some

papers is due to the action of active oxygen on the resin used in sizing the paper, or in some cases on the woody matter present in the paper. By means of dimethylparaphenylenediamine paper (this vol., p. 298), the presence and even the percentage amount of woody matter can be determined in a paper. When the moist dimethylparaphenylenediamine paper is pressed between paper containing wood, it acquires a deep red colour. Ordinary sized paper merely turns it a delicate rose colour. N. H. M.

Phosphorus Pentafluoride. By H. MOISSAN (Compt. rend., 103, 1257-1260). Perfectly dry phosphorus pentafluoride confined over mercury is not decomposed by the action of induction sparks 40 mm. in length, a result which agrees with Thorpe's earlier observation. With sparks 150-200 mm. in length, however, the gas is decomposed into phosphorus trifluoride and fluorine, the latter at once attacking the glass and the mercury,

Phosphorus pentafluoride yields no trifluoride when heated to dull redness with an excess of phosphorus. In this respect, its behaviour differs from that of the pentachloride. It is not affected by sulphur vapour at 440°, nor by iodine vapour at 500°. In presence of a minute trace of water, it attacks glass, with formation of silicon fluoride and phosphorus oxyfluoride, whilst the alkalis in the glass are converted into phosphates or fluorphosphates.

In order to analyse the gas, a measured volume was absorbed in water in a platinum vessel, treated with nitric acid and molybdic solution, and the phosphorus finally weighed as magnesium pyrophosphate. Another method consists in absorbing a measured volume in potassium hydroxide solution, which is mixed with some pure silica, evaporated to dryness, mixed with concentrated sulphuric acid, and heated until vapours of this acid begin to come off. The liquid is then diluted, made alkaline with ammonia, and the phosphorus precipitated as magnesium ammonium phosphate.

The results agree with the formula PF.; the first method is the

most accurate.

C. H. B.

Compounds of Selenious and Arsenious Anhydrides with Sulphuric Anhydride: Isolation of Sulphuric Anhydride. By R. WEBER (Ber., 19, 3185-3190).-When selenious anhydride is warmed with very carefully purified sulphuric anhydride, it dissolves therein, and if the excess of sulphuric anhydride is distilled off at 60 -70°, a crystalline compound, SeO2,SO3, is left. This substance is decomposed by a temperature of 100°, sulphuric anhydride being evolved. Water decomposes it with great violence.

In like manner, sulphuric anhydride dissolves arsenious anhydride. If the excess of sulphuric anhydride is distilled off at 60°, a compound of the formula As203,6SO, is left; if the distillation is continued at 100°, the residue has the formula As2O3,3SO3. These compounds are quite distinct from the compound As2O3,SO, discovered by Reich in 1863 in the Freiberg smelting works.

The author states that the specimens of pure sulphuric anhydride previously obtained and described (this Journal, 1877, ii, 164) still

« PreviousContinue »