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sium and ammonium have been isolated by Ditte. Nitric acid at first precipitates ammonium nitrate from its solution molecule for molecule, then a minimum of solubility is passed, and afterwards the solubility increases with the amount of acid. In the case of potassium nitrate, the minimum of solubility is very quickly passed, and the influence of the chemical change is in fact perceptible at the outset. C. H. B.

Critical Remarks on the Avidity Formula. By G. A. HAGEMANN (Ber., 20, 556-562).-Thomsen's theory of the avidity of acids (Thermochemische Untersuchungen, 1) has been apparently confirmed by Ostwald's investigations (Ann. Chem. Phys. Ergb., 8, 154, and 2, 429). The author points out, however, that Thomsen is inconsistent in regarding the solution in water of such substances as Na2O and SO, as purely physical phenomena, and yet introducing the attendant heat changes into the calculation of a chemical constant. Ostwald, who has studied the volume changes attending the mixture of an acid and a base, entirely neglects the influence of the water of solution; and the author shows that when this latter is taken into account the expression for the phenomenon is not simply (Na,OAq,SO,Aq), but is much more complex.

Every such reaction is in fact a double decomposition, and it is doubtful if Berthollet's problem was correctly stated, since the influence of the solvent water must always enter into it. In the author's opinion, however, although the calculations of "avidity" are entirely false, the agreement between Ostwald's and Thomsen's results is important as confirming his theory of the residual energy, basic or acid, of neutral salts (Studien über das Molecular-volumen einiger Körper). This theory has been strengthened by the experiments of Trey (this vol., p. 102), who has shown that haloïd salts in general accelerate the catalytic decomposition of methyl acetate by hydrochloric acid, their residual energy being acid, while sulphates in general retard it, their residual energy being basic. Solutions of acids, bases, and salts, are in reality chemical combinations in indefinite proportions. Cн. B.

Hagemann's Critical Remarks on the Avidity Formula. By J. THOMSEN (Ber., 20, 1155-1157).-According to the author Hagemann in his criticisms (preceding Abstract) confuses positive changes of volume and contractions, or negative changes.

Electrolysis of Hydrochloric Acid; a Lecture Experiment. By M. ROSENFELD (Ber., 20, 1154-1155).—In this paper, an apparatus is described to illustrate the electrolytic decomposition of hydrochloric acid, and the formation of a detonating mixture of hydrogen and chlorine. It consists of two concentric cylinders, the outer one of which serves for a steam jacket, and in the inner one is placed a mixture in equal volumes of hydrochloric acid and water, which has previously been saturated, when hot, with sodium chloride. This solution is electrolysed by two carbon poles connected with a battery. By the use of this apparatus, an explosive mixture of the two gases is obtained very rapidly. V. H. V.

Lecture Experiment. By C. SCHALL (Ber., 20, 915-916).— The specific heat of zinc is nearly twice as great as that of tin, and this, taken in conjunction with the fact that both metals have nearly the same specific gravity, renders them suitable for demonstrating Dulong and Petit's law for lecture purposes. Rods of the two metals of similar section and equal weight are heated to 150-170°, and then placed on paraffin-wax; the paraffin melted by each can be weighed, and is proportional to the specific heat of the metal in question.

W. P. W.

A Constant Gas Generator. By C. SLEENBUCH (J. pr. Chem. [2], 35, 364-368).-The essential part of the apparatus consists of a kind of U-tube, the one limb of which is of a shape suitable to contain the marble, zinc, manganese dioxide, &c., the other prolonged and terminating in a bulb. At the base of the U-tube, another tube is blown, which is fitted by means of a cork into a Woulff's bottle, and reaches nearly to the bottom of this. In the latter tube, a small side tube is sealed to enable the air in the Woulff's flask to be driven out by the liquid. In this way the spent and heavy acid flows into the Woulff's bottle (and may from time to time be syphoned off by a tube leading from the other neck of the bottle), while the available acid in the pressure tube is always the lighter and fresher acid. By surrounding the limb of the apparatus containing the manganese dioxide, &c., with a coil of metal tubing through which steam is passed, the apparatus may be used as a chlorine generator.

L. T. T.

Inorganic Chemistry.

Amount of Oxygen in the Atmosphere. By U. KREUSLER (Ber., 20, 991-999). The author has determined the amount of oxygen in the atmosphere for 45 consecutive days, and found only very slight variations, the extremes being 20-901 and 20-939 per cent. (compare Landwirtschaft Jahrb., 14, 305). Tables are given showing the percentage of oxygen obtained each day, and also the meteorological conditions under which the experiments were made.

N. H. M.

Boiling Point of Ozone: Solidification of Ethylene. By K. OLSZEWSKI (Monatsh. Chem., 8, 69-72).-Ozone was liquefied by passing a current of ozonised oxygen through a tube cooled by liquid oxygen boiling at atmospheric pressure. It liquefies with ease at -1814 to a dark-blue liquid, whilst the oxygen passes away through the open end of the tube. The boiling point of the liquefied ozone, determined by the aid of liquid ethylene, with a carbon bisulphide thermometer, was found to be 109°; this corresponds with -106° of the hydrogen thermometer. It is necessary to exercise great care in performing the above experiment on account of the readiness with which liquid ozone explodes with violence when it comes in contact with

ethylene gas. A small quantity of liquid ozone sealed up in a glass tube changed, at the ordinary temperature, to a bluish gas. Former experiments to solidify ethylene were unsuccessful (Abstr., 1885, 1101), but the author has now succeeded in solidifying this gas to a white, crystalline, somewhat transparent mass, by allowing the liquid gas to boil under a pressure of 1 mm. at the boiling point of oxygen (-181-4°). The melting point of the solid ethylene is -169°.

G. H. M.

Reaction of Nitrous Acid with Sulphurous Acid. By F. RASCHIG (Ber., 20, 1158–1163).—In a former paper (this vol., p. 549) the author has shown that hydroxylamine reacts with sulphurous acid to form an amido-sulphonic acid. In this preliminary communication, speculations are put forward regarding the possible reactions between free nitrous and sulphurous acids, with especial reference to the chemical changes which occur in the leaden chambers of the sulphuric acid manufacture. These speculations are not here, however, supported by experimental evidence. V. H. V.

Oxidation of Ammonia in Presence of Platinum or Palladium. By K. KRAUT (Ber., 20, 1113-1114).-If in the well-known experiment illustrating the oxidation of ammonia by means of a glowing spiral or foil of platinum, a current of oxygen is passed into the solution of ammonia, a white cloud of ammonium nitrate is at first produced, and subsequently fumes of nitrogen peroxide appear, which increase until an inflammable or even explosive mixture of gas is formed. V. H. V.

Hydroxylated Solid Hydrogen Phosphide. By B. FRANKE (J. pr. Chem. [2], 35, 341–349).-The so-called oxide of phosphorus is generally looked on as a mixture of phosphorous and phosphoric acids. Le Verrier (Annalen, 27, 167) obtained this substance in greater purity by exposing to the air phosphorus half covered with phosphorous chloride. The aqueous solution of the substance so obtained decomposed at 80° into free phosphoric acid and yellow flocks of a substance which he believed to be a hydrated oxide of phosphorus. The author has obtained the same substance by the action of water on P12 The iodide is prepared by mixing the required quantities of phosphorus and iodine in carbon bisulphide solution; this solution is then gradually added, with constant agitation, to water. No separation of phosphorus occurs, but the aqueous solution (of OH.P,H,HI) becomes of a golden-yellow colour whilst the carbon bisulphide becomes colourless. The aqueous layer is separated and heated to 80°, when it becomes colourless, deposits yellow flocks, and contains now only hydriodic and a little hypophosphorous acids. These flocks have the composition Р.Н.ОН. This substance decomposes, slowly under water, more rapidly in moist air, into hypophosphorous acid, phosphorus, and gaseous hydrogen phosphide. The analysis was made by heating strongly in a current of carbonic anhydride. The residue, consisting of amorphous phosphorus and phosphoric anhydride, was weighed, then oxidised with nitric acid, and re-weighed; the gaseous hydrogen phosphide evolved was measured.

This hydroxylated hydrogen phosphide dissolves in alcoholic potash with evolution of hydrogen from the compound to PH.OK, but on adding water to the solution decomposition takes place according to the equation

3PH.OK + 6H2O + 3KOH = 6KPH2O2 + 2PH, + 4P.

2

This substance forms part of the reddish-white coating which gradually covers phosphorus when kept under water.

The author finds that when hydrogen phosphide is acted on by dilute potash it is completely decomposed, probably according to the equations

2

4PH, + 4KOH= 4PH2OK + 4H2 = P,H2 + 5H2 + 4KOH. L. T. T. Hydrates of Potassium Hydroxide. By C. GÖTTIG (Ber., 20, 1094-1096).—In this paper, two new definite compounds of potash with water are described: of these, one has the composition 2KHO + 9H2O, separating from concentrated alcoholic solutions of the alkali (sp. gr. 105-1058) in pyramidal crystals, melting below 40°; when kept over sulphuric acid, it loses 3 mols. H2O. The second compound, 2KHO + 5H2O, is obtained by concentrating alcoholic solutions of potash until a boiling point of 116° is reached; on cooling, the liquid solidifies to a thick magma of interlaced needles. This compound melts below 50°, and when kept over sulphuric acid loses 1 mols. H2O, with formation of the hydrate KHO + H2O.

Both the above compounds, when introduced in small quantities into water, exhibit at first a peculiar rotatory motion and then dissolve rapidly. V. H. V.

So-called Argentous Compounds. By W. MUTHMANN (Ber., 20, 983-990). A microscopic examination of the crystals obtained by dissolving silver molybdate, chromate, and tungstate in ammonia to saturation, heating at 90°, and passing hydrogen for some time (Rautenberg, Annalen, 114, 119), shows that they consist of the unaltered salt crystallised with very finely divided metallic silver. Addition of ammonia dissolves the salt and leaves metallic silver undissolved; and if in the foregoing process ammonia is constantly added to replace that removed by the passage of hydrogen through the ammoniacal solution, only finely divided silver is obtained instead of the so-called argentous salts. Silver citrate when heated at 108° decomposes with the formation of metallic silver, and the aqueous solution is not coloured red; when the salt is heated at 100° in hydrogen, argentous citrate and citric acid are not formed as stated by Wöhler and v. Bibra (Annalen, 30, 3), but decomposition-products of citric acid (comp. Trans., 1887, 416) and finely divided silver are obtained together with unaltered salt. The product, contrary to the behaviour of so-called argentous salts, dissolves in ammonia without decomposing into finely divided silver and the corresponding silver salt; the solution is clear, intensely red, and feebly fluorescent, and when largely diluted with water appears transparent and grass-green by transmitted, but opaque and violet by reflected light. The colour of the solution is not due to the presence of argentous salt, but of

finely divided silver; it is instantly destroyed by the addition of acids or salts such as potassium nitrate and sodium sulphate or acetate, and silver is precipitated; shaking with recently ignited animal charcoal removes it, and on dialysis of the solution a deposit of silver is found on the membrane of the dialyser. Addition of gum arabic to the red solution and subsequent precipitation with alcohol removes the colour, and the precipitate gives a red solution with water; moreover, when it is kept at -12° for some hours and the ice formed subsequently melted, a liquid is obtained which is no longer red and transparent, but black and opaque, and deposits finely divided silver on standing. The author concludes, therefore, that argentous salts do not exist.

W. P. W.

Double Phosphates and Arsenates of Strontium and Sodium. By A. JOLY (Compt. rend., 104, 905-908).-The author has previously found (Compt. rend., 103, 1197) that the reaction between disodium phosphate (1 mol.) and strontium chloride (1 mol.) takes. place in three phases. A gelatinous trimetallic phosphate is formed, which then becomes crystalline, and is afterwards transformed into a distrontium phosphate, the neutral solution becoming acid to litmus. If the vessel is free from any crystals formed in a previous operation, the second and third stages can be distinctly separated. The thermometer remains stationary for some minutes, during which the crystalline trimetallic phosphate is isolated. It consists of cubic crystals of strontium sodium phosphate, NaSrPO, + 9H2O, almost insoluble in cold water and not decomposed by washing with water.

If the precipitate is allowed to remain in the liquid, and phenolphthalein is added and then aqueous soda, a white, gelatinous precipitate is formed which crystallises rapidly. When the indicator changes, one equivalent of alkali has been added, and the whole of the strontium is precipitated as strontium sodium phosphate, which is not affected by water.

When a solution of strontium chloride (1 mol.) is added to a solution of disodium arsenate (1 mol.), no precipitate is formed, and the solution remains alkaline, but after some time, if the sides of the vessel are rubbed, a crystalline precipitate gradually separates, and the liquid becomes acid to litmus but remains neutral to methyl-orange. If the liquid is not agitated, but crystallisation is allowed to take place very slowly, large, cubic crystals are formed and the reaction is complete in 24 hours. The crystals are strontium sodium arsenate, NaSrAsO + 9H2O; the mother-liquor is acid and some of the arsenate remains in solution. If, however, one equivalent of soda is added to the solution, precipitation becomes complete and the precipitate does not alter in contact with water. It likewise undergoes no change even if left in the acid solution.

Similar double salts seemed to be formed with calcium, but in the case of barium the transformation of the precipitate is so rapid that the formation of a double salt cannot be observed. C. H. B.

Ammoniacal Compounds of Cadmium Chloride. By G. ANDRÉ (Compt. rend., 104, 908-910).-When cadmium chloride is dissolved in well-cooled aqueous ammonia of 20 per cent., and a

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