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cæsium salt. The double salt 3RbNO2, Co(NO2)3 + H2O is prepared in a similar manner. They are both lemon-coloured crystalline salts, and resemble in their behaviour Fischer's potassium-compound, except in their solubility in water, the cæsium salt dissolving only in 20,100 parts of water at 17°, and the rubidium salt in 19,800 parts of water. The method employed in analysing these compounds is described.

Thallium also yields a double salt with cobalt nitrite; it is a red crystalline compound, soluble in 23,810 parts of water.

N. H. M. Decomposition of Glass by Carbonic Anhydride condensed on its Surface. By R. BUNSEN (Ann. Phys. Chem. [2], 29, 161165). Formerly the author attributed the absorption of carbonic anhydride by glass-wool rather to an interpenetration of the glass by the molecules of the liquefied gas rather than to any chemical change (Abstr., 1884, 146). This view would also be confirmed by the observations on the stability of glass towards the most concentrated hydrochloric acid. However, if the glass-wool be damp, whereby the absorption of the gas is remarkably increased (Abstr., 1885, 867), the possibility of a chemical change is not precluded. Accordingly the glass (49-453 grams) used in the experiment was exhausted with water, and a residue obtained from it corresponding to the decomposition of 2.882 grams of glass, or 5.83 per cent. of the whole. Even if the chemical change consists in the production at first of sodium carbonate, which would take up a further quantity of carbonic anhydride, corresponding with the formation of sodium hydrogen carbonate, which on subsequent heating would again be driven off, yet all the carbonic anhydride absorbed cannot be accounted for in this way. The phenomenon is thus not only one of chemical change, but also of absorption, the particular degree of each of which cannot be estimated.

If, then, carbonic acid can decompose glass, the same is to be expected of water. Observations in the course of experiments on the determination of the tension of aqueous vapour at high temperatures are quoted to show that glass tubes containing water-vapour when beated at 88° are converted into a white porcelain-like mass, and that their inner diameter is diminished by one-tenth.

V. H. V.

Note. On the decomposition of glass by carbonic anhydride under high pressures compare Pfaundler (Abstr., 1885, 868). V. H. V.

Purification of Yttria. By L. DE BOISBAUDRAN (Compt. rend., 103, 627-629).—A comparatively very pure sample of yttria was subjected to 32 series of fractionations by means of ammonia. The product of the last precipitation of the thirty-second series showed a less brilliant fluorescence than the original earth, and the bands of Za and Zẞ in the spectrum had diminished considerably in intensity, whilst the bands of samarium retained their original vigour. The colour of the fluorescence had changed from yellowish-green to orange-yellow.

This last precipitate was submitted to 26 series of fractionations by means of oxalic acid. The brilliancy of the fluorescence continu

ally diminished, but, contrary to the phenomena observed during the first fractionation, the samarium bands diminished in intensity much more rapidly than the bands of Za and ZB. The earth from the oxalate precipitated at the end of the fifth fractionation showed very faintly the citron band and the double green band of Za and Zẞ, with a trace of the red bands of samarium. The oxalate from the twenty-sixth fractionation yielded a very white earth which showed a trace of the citron band of Za, but none of the red, green, blue, and violet bands in the spectrum described by Crookes. This yttria gave no fluorescence when mixed with lime, but its hydrochloric acid solution brilliant spark spectrum of yttrium.

gave a

The sulphate prepared from the last precipitate from the fractionation with oxalic acid gave a rose-coloured fluorescence due to the presence of a trace of bismuth.

C. H. B.

Heating and Cooling of Cast Steel. By OSMOND (Compt. rend., 103, 743—746).—The phenomena which accompany the heating and cooling of cast steel were investigated by means of a thermoelectric couple connected with an aperiodic galvanometer.

Barrett observed that when a bar of hard iron is cooled from a white heat there is a sudden development of heat at dull redness, and the magnetic properties of the iron change abruptly. He distinguished this phenomenon by the name recalescence. Chatelier and Pinchon found that at about 700° a molecular modification of pure iron is formed.

The author's experiments show that as the proportion of carbon increases from 016 to 1.25 per cent. the temperature at which the molecular alteration takes place falls, whilst the point of recalescence rises, until in hard steel the two points coincide. The rate at which heating takes place has no influence on the temperature at which the two changes take place, but these temperatures are affected by the rate of cooling, and are lower the greater the rapidity with which cooling takes place. In quick tempering, no such phenomena are observed; the heat corresponding with the non-effected changes remains in the iron. The two critical points also fall somewhat if the initial temperature of heating is raised. During annealing after tempering, the latent heat of tempering is liberated gradually and not abruptly.

C. H. B.

Tungsten. By T. KNIESCHE (Chem. Zeit., 10, 1067—1068).—In treating tungsten ores, sodium tungstate is first obtained, then from this tungstic acid, which in its turn is reduced at a temperature of 1600° to metallic tungsten. The preparation of the chemically pure metal is simply a question of time; any way, as obtained at present, it is useful in steel making. It must be added only when the iron is in a perfectly fluid state. Sodium tungstate is used for rendering inflammable materials fireproof. D. A. L.

Titanium. By O. v. PFORDTEN (Annalen, 234, 257-299).-The sulphides of those metals which have a strong affinity for oxygen cannot be obtained in the pure state by passing carbon bisulphide over the metallic oxides at a red heat, but they can be prepared by the

action of pure sulphuretted hydrogen on the metallic chlorides. The gas must be passed through chromous chloride to remove traces of oxygen, and is then dried by means of phosphoric oxide. The author disputes Thorpe's statement (Trans., 1885, 492) that sulphuretted hydrogen can be dried by passing the gas through sulphuric acid. At the ordinary temperature, sulphuretted hydrogen reduces titanic chloride to titanous chloride; at a higher temperature, a compound is precipitated, which is probably a sulphochloride. Crystals of titanium disulphide, TiS2, are deposited when sulphuretted hydrogen and the vapour of titanium tetrachloride are passed through a red-hot tube from which atmospheric air has been carefully expelled. The bisulphide is not attacked by hydrogen at a red heat in the presence of an excess of sulphuretted hydrogen. At a red heat, it is oxidised completely by carbonic anhydride, and it splits up into the sesquisulphide, Ti,S,, and sulphur in an atmosphere of hydrogen or nitrogen. The sequisulphide is a metallic grey substance, insoluble in sodium hydroxide solution; it dissolves in nitric and strong sulphuric acids with a green coloration. The author is of opinion that the sesquisulphide described by Thorpe (loc. cit.) is an impure substance, and that its green colour is due to the presence of vanadium.

The sesquisulphide is reduced to monosulphide by hydrogen at a higher temperature than that at which refractory glass softens. The crystals of the monosulphide are dark red. Dilute nitric acid attacks the monosulphide with difficulty; in other respects, this substance resembles the sesquisulphide. W. C. W.

Atomic Weight of Germanium. By L. DE BOISBAUDRAN (Compt. rend., 103, 452-453).-Winkler's recent determination of the atomic weight of germanium, 72:32 (Abstr., 1886, 985), agrees perfectly with the value calculated by the author from the wave-lengths of the lines in the germanium spectrum (Abstr., 1886, 768). The law of proportionality between the variations in the atomic weights of the elements, and the variations in the wave-lengths of the lines in their respective spectra, thus receives further confirmation.

C. H. B.

Gold Oxides. By G. KRÜSS (Ber., 19, 2541-2549).-Aurous oxide, Au2O, could not be obtained in the pure state by any of the known methods. It is prepared by treating the double bromide of gold with aqueous sulphurous acid at 0° until the intense red colour of the bromide has disappeared. The colourless solution of aurous bromide so formed is warmed with potash, which causes a separation of aurous hydroxide. The oxide is dark violet when moist, greyishviolet when dry; when freshly precipitated, it dissolves in cold water, yielding an indigo-coloured solution with a brownish fluorescence; it is insoluble in hot water. The solution has a characteristic absorption spectrum showing a band at 5870. Hydrochloric and hydrobromic acids convert it into gold and the corresponding auric compounds; other acids have no action. The hydroxide parts with water at 200°, and at 250° gives up its oxygen.

Aurosoauric oxide, Au,O, (compare Schottländer, Abstr., 1883, 853),

is prepared by gradually heating pure auric hydroxide up to 160° until the weight remains constant. It is a fine dark yellowishbrown powder, is very hygroscopic, and can only be kept over phosphoric anhydride. When heated above 173°, it gives off oxygen.

Auric oxide, Au,O,, is conveniently obtained by treating auroauric chloride (1 part) with water (50 parts), boiling the solution, and adding finely powdered magnesia alba, stirring the whole time, until the red colour of the auric chloride has disappeared. The gold trihydroxide is filtered, mixed with water (20 parts), treated with nitric acid, sp. gr. 14 (10 parts), and left for 24 hours. The residue, after filtering, is mixed with an equal amount of water and nitric acid, and heated for six hours at 100°. The undissolved portion is now free from magnesia, and is washed with water to remove nitric acid. The pure auric hydroxide has a yellowish-brown colour when moist, and is rather readily soluble in nitric acid. When kept for weeks over phosphoric anhydride, it is converted into aurylic hydroxide, AuO-OH, and when carefully heated yields auric oxide. The so-called "purple oxide of gold" appears to be gold in a finely

divided state.

The author was unable to obtain Prat's gold superoxide and Figuier's auric acid (Compt. rend., 70, 844), or any other oxide of gold than the three described. This behaviour of gold is in accordance with the position (between platinum and mercury) assigned to it in the periodic arrangement of the elements. N. H. M.

Solubility of some Gold Compounds. By T. ROSENBLADT (Ber., 19, 2535-2538).-The following table shows the amounts of the anhydrous double salts contained in 100 parts by weight of aqueous solution at the given temperatures :

10°. 20°. 30°. 40°. 50°. 60°. 70°. 80°. 90°. 100°.

NaAuCl, 58.2 60.2 64.0 69.4

67.3

77.5 90.0
72.0 76.4

81.0 85.7

59.2

70.0 80.2

LiAuCl 53.1 57.7 62.5
KANCI 27·7 38.2 48.7
RbAuCl 46 9.0 13.4 17.2 22.2 26.6 31.0 35.3 39.7 44.2
CsAuCl 0.5 0.8 1.7 3.2 54 8.2 12.0 16.3 21.7 27.5

The solubilities of the double salts (with exception of the lithium salt) are inversely proportional to the molecular weights of the salts. N. H. M.

Mineralogical Chemistry.

Artificial Breithauptite from the Mechernich Lead Furnaces. By A. BRAND (Zeit. Kryst. Min., 12, 234-239).—In 1885 the author found a number of peculiar crystals in the clay used for stopping the tap-holes of the lead furnaces in which antimonial lead was smelted. They occur in all the furnaces; the clay being pulverised and used again. It is therefore impossible to determine whether they were originally formed in the smelting of hard lead. The crystals were columnar, hexagonal prisms, 01 to 0.5 mm. thick, and 5 to 26 mm. long. They were brittle, had an uneven fracture, adamantine lustre, steel-grey to copper-red colour, and greyish-brown streak. The hardness was 5 to 5.5, and the sp. gr. about 8. Analysis of carefully purified material gave the following results :

-

[blocks in formation]

Chemical Composition of Butyrellite. By W. I. MACADAM (Min. Mag., 6, 175-180; Zeit. Kryst. Min., 12, 182).-In the investigation of ten samples of bog-butter or butyrellite (Dana) from various localities in the peat bogs of Scotland and Ireland, the author found that the portion of the butyrellite soluble in ether corresponded in all respects with the substance obtained under like conditions from ordinary butter. This portion varies in the ten analyses from 9152 to 98-94 per cent. The portion insoluble in ether, 0.38 to 4:56 per cent., was slightly soluble in water, and gave evidence of the presence of milk-sugar. The portion insoluble in water contained nitrogen, and gave on combustion the peculiar odour of burning cheese. The ash or mineral portion, 0.01 to 0.36 per cent., contained traces of phosphoric acid. These results, and the fact that a number of cow's hairs were found in the samples, show that butyrellite has no claim to be called a mineral. It cannot be discussed how these masses found their way into the positions from which they are now obtained. It is, however, obvious that the material is not of mineral or even of resinous origin, but of undoubted animal derivation, and should therefore be erased from the list of minerals. B. H. B.

Minerals from Vesuvius. By E. SCACCHI (Zeit. Kryst. Min., 12, 202-203).-1. Hydrogiobertite is the name given by the author to a new hydrated magnesium carbonate, which occurs in the form of grey, compact masses 2 to 15 mm. in diameter. With the lens, minute magnetite crystals are observed enclosed in the mass. The sp. gr. is 2-149 to 2:174. The loss on ignition amounted to 53:07 per cent. Of the sample, 0.507 gram contained 0·0025 gram of magnetite, and 0·022 gram of ferric oxide which was subtracted as limonite with the magnetite. The results of the analysis were as follows:

VOL. LII.

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