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crystals, which probably belong to the triclinic system. They have the composition Na2O,ThO2,P2O5. Zirconium oxide or phosphate added to the fused pyrophosphate, yields a crystalline powder. Zirconium chloride added to the pyrophosphate together with a small quantity of sodium chloride, yields hexagonal plates, which act very feebly on polarised light, and are soluble in acids. Sp. gr. at 14° = 2.88. They have the composition 6Na,0,3ZrO2.4P2O. With a larger quantity of sodium chloride, the compound 4Na2O,ZrO2,2P2O3, is obtained in prisms which act strongly on polarised light, and have a negative bisectrix. They are soluble in acids. Sp. gr. at 14°

= 2:43.

On account of its comparative infusibility, normal sodium phosphate alone yields no similar products, but when mixed with sodium chloride it yields the same products as the pyrophosphate.

Thorium sodium and zirconium sodium metaphosphates are similar to one another and to the corresponding potassium compounds (loc. cit.), but they are not isomorphous. The double pyrophosphates are not analogous to one another either in form or composition. These results afford no evidence as to the true atomic weight of thorium and the formula of its oxide.

C. H. B.

Vanadates. By A. CARNOT (Compt. rend., 105, 119-122).— When ammonia is added gradually to a cold acid solution containing vanadic acid, the yellow colour becomes deeper and deeper, up to the point at which the reaction becomes neutral; the colour persists for a long time if the liquid remains cold. Conversely, if an acid is added gradually to a colourless alkaline solution of a vanadate, the yellow colour appears as soon as the reaction becomes acid, but diminishes in intensity when excess of acid is added. These facts indicate that in almost neutral solutions acid vanadates are formed with a deeper colour than that of vanadic acid itself. The reactions of such solutions with metallic salts are different from those observed under ordinary conditions, various acid vanadates being formed. In order to ensure the formation of normal vanadates, an ammoniacal solution should be only partially neutralised, or the liquid should be boiled in presence of a slight excess of ammonia.

Cobalt and Nickel.-Cobalt nitrate and vanadic acid in a solution exactly neutralised with ammonia give an orange precipitate of the vanadate CoO,V2Os. Precipitation is complete after several hours if the liquid is neutral, but takes place more slowly in presence of any ammonium salt other than the nitrate. Nickel yields a similar precipitate, but its formation takes place more slowly, and is prevented by the presence of ammonium nitrate. Hot solutions of nickel and cobalt salts yield respectively pale-yellow and brown precipitates, but precipitation is always incomplete, and is prevented by ammonium

chloride.

Zinc salts with neutral vanadates give yellow precipitates, which become white when heated. Zinc nitrate and ammonium vanadate yield a white precipitate, easily soluble in acids and in ammonia, the whole of the vanadic acid being precipitated.

Cadmium salts in neutral solutions yield a white precipitate, readily

soluble in the slightest excess of acid or ammonia. Precipitation is always incomplete.

Copper salts in the cold give a greenish-yellow precipitate of the vanadate CuO,V2O5, which becomes greenish-brown when heated. If the solution is hot, the precipitate is brownish-yellow, and becomes black when boiled. It has the composition 2CuO,V2O5. In both cases precipitation is incomplete, and if ammonium sulphide is added. a black precipitate is formed, and the liquid is brown; the precipitated sulphide contains vanadium, and the liquid contains copper. On acidifying the liquid, a rose-brown copper vanadium sulphide is precipitated. Arsenates and copper salts behave in a similar manner.

Mercurous nitrate in neutral solutions precipitates the whole of the vanadic acid in the form of the orange vanadate, Hg2O,V2O. In presence of a slight excess of ammonia, a grey or blackish precipitate of complex composition is formed. When these precipitates are heated in hydrogen sulphide, vanadium sulphide is left in a pure condition, and this method may be used for the isolation and estimation of vanadium. Mercuric chloride produces no precipitate if the solution is acid, but on adding ammonia, a pale-yellow precipitate is formed. If the liquid is neutral when the mercuric chloride is added, the precipitate is white. Precipitation is complete, and this method also be used for the isolation of vanadium in the manner just described.

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Lead salts yield a precipitate which is pale yellow in presence of a slight excess of acetic acid, yellowish in presence of a slight excess of ammonia. Precipitation is almost complete in neutral solutions.

Bismuth nitrate precipitates the whole of the vanadic acid as a yellowish-white precipitate on addition of ammonia. If the liquid is slightly acid, an orange precipitate is formed on boiling, but precipitation is incomplete. If the acid liquid is mixed with sodium acetate and then boiled, a bright yellow precipitate of the vanadate Bi2O,V205 is formed. This becomes orange when heated, but regains its yellow colour on cooling.

C. H. B.

Atomic Weight of Gold. By G. KRÜSS (Ber., 20, 2365-2368). -Referring to the discrepancy between his own (this vol., p. 778) and Thorpe and Laurie's (Trans., 1887, 565) determinations of the atomic weight of gold, the author points out that in one of his papers on gold (Annalen, 238, 265), he has shown that potassium aurobromide always contains about 0:05 per cent. of free gold, probably formed during crystallisation by the reducing action of organic matter in the air. Thorpe and Laurie have not taken account of this fact. Applying this correction to Thorpe and Laurie's determination, the atomic weight obtained by means (1) of the ratio Au: KBr becomes 196-616; (2) of the ratio Au: Ag, 196·559; (3) of Au: AgBr, 196·575, or lower than the number 196-64 previously obtained by the author. The author therefore upholds the correctness of his determinations. L. T. T.

Gold Sulphides. By L. HOFFMANN and G. KRÜSS (Ber., 20, 2369-2376).-The statements given in various text-books concerning the sulphides of gold are very conflicting, compounds Au,S,

Au2S2, and Au2S, being variously given. The sulphide Au2S, is perhaps usually accepted, the existence of the other two very often disputed. These conclusions are, however, by no means justified. Berzelius believed he obtained Au,S by passing hydrogen sulphide into a boiling solution of auric chloride. Levol, on the other hand, states that under these conditions free gold is alone deposited. The author finds that Levol's statement is correct, if care is taken to keep the temperature of the whole solution at 100°. If local cooling takes place the precipitate contains varying proportions of combined sulphur, but no definite compound can be obtained. In all their experiments the authors washed the precipitated sulphide by decantation with water, alcohol, ether, and carbon bisulphide successively. They found that the free sulphur was retained very firmly, and could not be completely removed by washing on the filter.

When hydrogen sulphide was passed through a solution of potassium aurocyanide, no apparent change took place, but when excess of hydrochloric acid was added, and the whole heated, aurous sulphide, Au,S, was precipitated as a steel-grey precipitate. This was carefully washed as above, and obtained in a dry state as a brownish-black powder of constant composition, corresponding with the above formula. When freshly precipitated, it dissolves in water to a brown solution. It is therefore necessary in purification to wash it with water containing hydrochloric acid, in which it is not soluble. When once dried, it is no longer soluble in water. It is not decomposed when boiled with dilute hydrochloric or sulphuric acids. Aqua regia, chlorous oxide, and other oxidising agents oxidise it easily. Bromine-water slowly dissolves it, with formation of AuBr, and sulphuric acid. Alkaline monosulphides dissolve it but slowly and slightly, polysulphides rapidly and completely, with the formation of green solutions of sulpho-salts. Caustic potash solution does not attack it even at 100°, whereas the compound Au2S2 is, under like conditions, decomposed into gold, potassium gold sulphide, and potassium gold oxide. Potassium cyanide dissolves it readily, and the sulphide is reprecipitated by boiling the solution with excess of hydrochloric acid. This reaction gives a good means of purifying the sulphide from free sulphur, as a slightly warmed solution of potassium cyanide dissolves the former and not the latter. When heated in a tube, part of the sulphur distils off, and part passes off as sulphurous anhydride. The compound is completely decomposed at 240°, and ignites in oxygen at a low temperature. When heated in a stream of hydrogen, hydrogen sulphide is formed, but in a stream of hydrogen chloride the sulphur sublimes without the formation of any hydrogen sulphide, and pure gold is left.

The existence of a soluble aurous sulphide and a soluble aurous oxide (Krüss, Untersuchungen über das Atomgewicht des Goldes, München, 1885) speaks strongly in favour of placing gold in the alkali-group rather than in the platinum-group.

L. T. T.

-

Mineralogical Chemistry.

Trona, Idrialine, and Zinc-bloom. By V. V. ZEPHAROVITCH (Zeit. Kryst. Min., 13, 135-144).-1. Crystals of Trona, Na,CO1 + 5H2O. The author has measured 50 crystals of trona from the soda works of Ebensee. The axial ratio he found to be a:b:c= 2-8459 : 1 : 2·9696. ß = 77° 23'. Analysis gave the following results:

CO2. Na2O. H2O. Na2SO4. Total.
38.93 40.77
0.20

19.96

99.86

Sp. gr. 2.14

2. Idrialine Crystals from Idria.-The discovery of idrialite in pistachio-green nodules in the Idria mercury mines was announced by R. Scharitzer (Abstr., 1883, 427). In 1886, specimens of a new variety were found. The specimens are of a yellowish-green to sulphur-yellow colour, and consist of pure idrialine. Microscopic examination shows that the plates belong to the monoclinic system.

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3. Fibrous Zinc-bloom (Hydrozincite) from Carinthia. It has hitherto not been observed that hydrozincite frequently exhibits a finely fibrous texture, especially in the reniform masses produced from the alteration of smithsonite. Analysis of some remarkably fibrous specimens of hydrozincite on galena recently obtained at Bleiberg, gave the following results (I) :—

H2O. Fe2O3. SiO2. Total.
0.42 0.36 100.15

CO2.
I. 17.05
II. 17.05

ZnO. • РЬО. 70.76 1.26 69.79 1.26

10.30 10.12

After subtracting the percentages of silica present as hemimorphite, and of iron present as limonite, the remainder (II) corresponds with the formula 4ZnCO, + 5Zn(HO)2 + H2O. This formula does not agree with any yet given. B. H. B.

Turquoise from the Kirghise Steppes. By N. J. v. KOKSCHAROFF (Zeit. Kryst. Min., 13, 187).-A greenish-biue mineral from the Karkaralinsk district of the Province of Semipalátinsk gave on analysis the following results :

Loss on ignition.

Total.

P2O Al2O3. Fe2O3. CuO,
Sp. gr.
34.42 (35.79) 3.52 7.67 18.60 100.00 2.887

These results show that the new turquoise is characterised by an exceptionally high percentage of copper. It is not soluble in hydrochloric acid or nitric acid, although it is in alkalis.

B. H. B.

Epsomite from Poland. By W. K. ZGLENITZKIJ (Zeit. Kryst. Min., 13, 200—201).—In an abandoned level in the Tscharkoffy Sulphur Mines, the author observed an efflorescence having a saline bitter taste. Analysis showed that the mineral had the composition MgSO4,7H2O. Hitherto, epsomite has not been found in Russia any

VOL. LII.

3 z

where except in the Siberian Steppes. At Tscharkoffy, it occurs in an argillaceous marl, of Upper Cretaceous age, in which well-preserved remains of Ananchytes ovata are found. The marl contains magnesia, and encloses beds of gypsum and sulphur. The hydrogen sulphide, formed from the decomposition of gypsum in the presence of organic remains, may be detected throughout the mine, and, on decomposition, yields sulphur and sulphuric acid or epsomite. B. H. B.

Augite from the Whin Sill. By J. J. H. TEALL (Zeit. Kryst. Min., 13, 180-181).-The author gives the following two analyses of augite I, from the normal Whin Sill (diabase containing bronzite), from Cauldron Snout; sp. gr. about 33; II, from the coarsest variety of the Whin Sill rocks, half a mile south of Tyne Head; sp. gr. 3:33.

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The analysis of the first augite corresponds with the formula 14CaFeSi2O + 5CaMgSi2O, + 6Mg2Si2O。 + 3MgAlSiO, + MgFe2SiO..

Andesine from Scourie Bay, Sutherlandshire. TEALL (Zeit. Kryst. Min., 13, 181).-A vein of nearly occurs in a dyke of hornblende schist at Scourie Bay. cleavage of the felspar is parallel to the brachypinacoid. is about 2-644. Analysis gave the following results :SiO2. Al.Og. CaO. MgO. Na O. 58.16 26.66 5.79

0.65

6.99

KO.

B. H. B.

By J. J. H. pure felspar The principal The sp. gr.

1.76

Total. 100.01

B. H. B.

Minerals from Porthalla Cove, Cornwall. By J. H. COLLINS (Zeit. Kryst. Min., 13, 180).—The author gives the following analyses of minerals from the rocks of Porthalla Cove:

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5.08 4:08 11.95 28.50

8:80} 8·12 10-74

-74{

8.581 2.84 4:50

0.10 trace 1.51 10:51 17.08

trace

33.62 32.80 34.65

[blocks in formation]

3:31 0.29 0.10 12.82

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S 0.46 0.55
13.70 12:00 8.69 3.20 1.50

1.85 0.51

0.10

lost on ignition..

Totals ....... 100.00 100.00 100.00 100.00 100.00 99-18

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