ductility is more decisive, and with 10 per 1000 of bismuth the alloy was very brittle and had a granular fracture; the mode of cooling had no appreciable effect on the ductility of these alloys. Other experiments with Indian coinage bars show that the ductility of bullion is not materially affected by the presence of 0.5 per 1000 of bismuth.

As the refining fine silver containing bismuth is both tedious and attended with loss of silver, the author suggests dilution with silver free from bismuth as a practical means of overcoming the brittleness. The author remarks on the concordance of his results with those of Gowland and Koga (Trans., 1887, 410-416), as regards the question of brittleness. The discrepancy in reference to refining bismuth silver he suggests is possibly due to the Japanese silver containing more base metals than the Indian silver; it consequently supplied more slagging material and greater facilities for refining.

D. A. L.

Combination of Silver Chloride with Metallic Chlorides. By M. C. LEA (Amer. J. Sci., 34, 384-387).—If hydrochloric acid is mixed first with ferric chloride and then with silver nitrate, the silver chloride which forms is not white but buff-coloured. The ferric chloride cannot be removed by washing, and is only partially removed by treatment with hydrochloric acid. The presence of the minute quantity of ferric chloride makes the silver chloride remarkably less sensitive to light.

Cobalt chloride and hydrochloric acid give a silver chloride which is pink and contains cobalt; but the reduction in the sensitiveness to light is very much less than when iron is present. Nickel and manganese behave similarly, but cupric chloride seems to have no tendency to combine with silver chloride. The tendency of gold chloride to combine with the silver chloride is, however, well marked, and the precipitate has a reddish shade, but the influence on the sensitiveness is not easily determined, since the gold is rapidly reduced to the metallic state, and the silver chloride darkens to black instead of to chocolate or violet as would be the case if it were pure.

In analytical determinations, it is important to digest the silver chloride for a considerable time with hydrochloric acid, and even then it is doubtful if the foreign chloride is entirely removed, especially if it is ferric chloride.

These observations show that silver chloride has a great tendency to combine with small quantities of other chlorides, and supports the author's view as to the nature of the "photo-salts " (this vol., p. 1). They also explain the fact that a small quantity of mercuric chloride very greatly reduces the sensitiveness of silver chloride to light. In order to ascertain the presence of mercury in the silver chloride, the author employs a solution of stannous chloride in hydrochloric acid which has no action on silver chloride if light is carefully excluded, but gives a brown or brownish-black colour to the precipitate if mercury is present. The author was unable to remove mercuric chloride from silver chloride even by very prolonged washing.

Poitevin's observation that his coloured photographic images resisted the action of light better after they were treated with dextrin and

lead chloride is explained by the tendency of the lead salt to prevent alteration of silver chloride. C. H. B.

Silver Potassium Carbonate. By A. DE SCHULTEN (Compt. rend., 105, 811-813).—When silver carbonate is formed by the action of an alkaline carbonate on silver nitrate, the precipitate is sometimes white, sometimes yellow, but always becomes yellow when washed. If silver nitrate is added to an excess of a concentrated solution of potassium carbonate containing some hydrogen carbonate, a white precipitate is formed which changes to microscopic crystals of the composition AgKCO3. This compound is decomposed by water, with removal of the potassium carbonate and formation of yellow silver carbonate.

150 grams of potassium carbonate is dissolved in 150 c.c. of water, cooled and agitated with 15 grams of potassium hydrogen carbonate. When the liquid is saturated with the latter salt at the ordinary temperature, it is filtered and mixed with a solution of 1 gram of silver nitrate in 25 c.c. of water. In order to obtain large crystals, the liquid containing the precipitate is heated with continual agitation. The precipitate dissolves, and when the liquid is cooled it deposits long, transparent crystals with a brilliant lustre; sp. gr. 3-769. They do not blacken when exposed to light except in the presence of organic matter, and when treated with water, the silver carbonate which remains retains the form of the original crystals. When heated, the compound loses carbonic anhydride, and at a higher temperature the silver oxide which is formed gives off oxygen.

The crystals are microscopic, rectangular lamella with a terminal angle closely approaching 90°. The refraction is almost identical with that of apatite; the extinction of parallel polarised light takes place longitudinally; twinning plane parallel with the plane of the optical axes; sign of elongation positive; maximum birefractive power approximately 0.0216. C. H. B.

Lead Aluminium Sulphate. By G. H. BAILEY (J. Soc. Chem. Ind., 6, 415).—The author has examined some crystals which have been noticed in a mordanting liquor (aluminium nitroacetate) prepared by dissolving up alum, lead acetate, and lead nitrate in water and allowing to settle. The crystals form octahedra crystallising in cruciform aggregates like alum. They are, however, not transparent and are quite unaltered by exposure to air. The substance is a lead alum, Pb,Al(SO.), + 20H2O, formed under special conditions of concentration and temperature.

D. B.

New Oxide of Thallium. By A. PICCINI (Gazzetta, 17,450-452).Carstanjen has observed that when a rapid current of chlorine is passed through a concentrated solution of potash in which thallium sesquioxide is suspended, the solution acquires a violet colour which is considered to be due to a potassium thallate. The same liquid is also formed when thallium hydroxide is submitted to electrolysis, using a plate of thallium as an electrode, as also on adding potassium hypochlorite to a quarter of its weight of caustic potash to which thallium sulphate is subsequently added. On digesting the whole and adding barium nitrate, a violet precipitate is finally obtained. The results of

analyses made to determine the relation between thallium and barium in this precipitate led to discordant results, but sufficient evidence was afforded to point to a formula, TIO2, for the oxide of thallium. The isolation of this oxide brings out a further point of analogy of the thallium compounds to those of lead. Experiments made to prepare the corresponding sulphur compound have not as yet been successful, although substances have been obtained which contain a proportion of sulphur greater than that required for the trisulphide. V. H. V.

Constitution of Basic Salts. By S. U. PICKERING (Chem. News, 56, 210-212).-In the author's opinion, those basic compounds, which although seemingly of indefinite composition can scarcely be regarded as mere mixtures, are precisely analogous to the complex hydrates, which he contends constitute a solution of a salt in water. Hydrated basic salts of copper may be obtained of a composition corresponding with that of an anhydrous salt of the formula 17CuO, SO3, but the most basic definite sulphate known is 4CuO,SO,, therefore if these higher basic salts are to be regarded as mixtures, they must be mixtures of a basic salt with copper hydroxide and not mixtures of two different basic salts,

To investigate this point, a series of basic copper salts were prepared by diluting a solution of ammonio-copper sulphate with increasing quantities of water; the precipitates were dried in a vacuum, and analysed. The results, although not decisive, tend to show that free copper hydroxide is not present in these compounds, for on comparing any two preparations of different basicity, the excess of copper oxide present in the more basic one is not accompanied by a constant proportion of water. D. A. L.

Crystallised Mercurous Iodide and Bromide. By A. STROMAN (Ber., 20, 2818-2823).—If a saturated solution of mercurous nitrate, as free as possible from oxide and slightly acidified with nitric acid, is heated to boiling with iodine, the latter becomes covered with a yellow powder, which partially dissolves, and the solution, after decantation into a warm dish, deposits, in the dark, lustrous, yellow, transparent, tetragonal scales of mercurous iodide; these must be dried in the dark at the ordinary temperature. When the mercurous

nitrate solution is treated with an alcoholic solution of iodine in the cold, small, yellow spangles of mercurous iodide are obtained, but the product formed by the old methods of preparation, that is, by rubbing together molecular proportions of mercury and iodine, and by adding potassium iodide in solution to a solution of a mercurous salt, have a green colour, and are impure, although the pure yellow compound can be obtained by reversing the last process and adding an excess of a dilute solution of mercurons nitrate to potassium iodide in solution. The crystallised compound shows the same colourchange as observed by Yvon (this Journal, 1873, 1105), but the change does not begin at 60°, as stated by him, since the salt is still a pure yellow at 100°, and only passes from this colour through dark yellow and orange to garnet-red at higher temperatures. Sublimation commences at 110-120°, not at 190° as stated by Yvon, and the

salt fuses at 290° with decomposition. Towards acids and solvents, the crystallised compound behaves like that precipitated by potassium iodide; ammonia and caustic alkalis render it green, and on heating convert it into the corresponding alkaline iodide and metallic mercury. The crystallised iodide is less sensitive to light than the precipitated yellow compound, which rapidly becomes black even in diffused daylight.

When mercurous nitrate solution is treated with bromine under similar conditions, small, white, nacreous, tetragonal scales of mercurous bromide are obtained, and the same compound separates in yellow, crystalline spangles when an alcoholic or aqueous solution of bromine is employed. It sublimes at 340-350° in small scales, is less sensitive to light than the iodide, dissolves in hot sulphuric acid with the evolution of sulphurous anhydride, becomes black and gradually decomposes when heated with dilute and concentrated hydrochloric acid, dissolves slowly in hot nitric acid (sp. gr. = 1.42), and decomposes with the formation of the corresponding bromides when treated with ammonia and caustic alkalis. W. P. W.

Atomic Weight of Yttrium Metals in their Natural Compounds: Gadolinite. By C. RAMMELSBERG (Ber. Akad. Ber., 1887, 549-556).—According to Nordenskiöld (Abstr., 1887, 109), the oxides of the yttrium metals occur in their natural compounds in proportions so nearly constant that he suggests the term gadolinium oxide for this mixture of yttrium, erbium, and ytterbium oxides.

The author shows from the results of 29 analyses of minerals from different sources and by various chemists, that this mixed oxide, so far from being constant, would give atomic weights varying from 97.5132.5° for the mixture of metals.

Analyses of gadolinite from Hitterö and Ytterby gave the following results:

Water of Crystallisation of Alums. By J. JUTTKE (Chem. Centr., 18, 777).-Potash alum, in a vacuum over sulphuric acid, loses 19 mols. H2O, chromium alum 12-13, and iron alum, 20-21 mols. HO. Potash alum, heated at 100° in a current of dry air, loses 15 mols. H2O readily, but the remainder only after prolonged heating, and breaking up of the dry crust, which retains the water. At a temperature of 20-30° potash alum gives off no water, at 42° 11 mols., at 65-91° 19 mols., and at 100° the remaining 5 mols. of water are

given off. Potassium, chromium, and ammonium iron alum heated at 100° are completely dehydrated, without becoming insoluble in water, and without undergoing any decomposition.

V. H. V.

Action of Hydrogen Sulphide on Cobalt Salts. By H. BAUBIGNY (Compt. rend., 105, 751-754, and 806-809).-The action of hydrogen sulphide on solutions of cobalt salts varies, as in the case of nickel salts (Abstr., 1882, 1031), with the concentration of the solution, the nature of the acid in the salt, the ratio between the weight of acid and metal present, the ratio of free acid to the water present, the degree of saturation with hydrogen sulphide, or in other words the tension of the gas, and also with certain other conditions, including the temperature and the duration of the experiment.

Solutions of the normal sulphates of cobalt and nickel were saturated with hydrogen sulphide, and hermetically sealed in glass flasks, the liquid occupying about five-sixths of the volume of the flask. After standing for some days, precipitation is always more complete in the case of nickel than with cobalt. This, however, is only a special result. Under comparable conditions the formation of cobalt sulphide from a solution of a cobalt salt is always more rapid than the formation of nickel sulphide from the corresponding nickel salt. This is observed, for example, if the solutions saturated with hydrogen sulphide only partially fill the vessels. It follows that the tension of the gas exercises a considerable influence on the result.

Precipitation of the cobalt sulphide is prevented by the presence of free acetic acid, the proportion required to produce this result being greater the greater the concentration of the solution. More acetic acid is necessary to prevent the precipitation of cobalt than to prevent that of nickel. With sulphuric acid and similar acids, however, the differences between the two metals tend to disappear. In both cases, there is no precipitation even after several days at the ordinary temperature if the proportion of free sulphuric acid is equal to half that in combination with the metal, provided that the quantity of salt. present exceeds 0.15 gram per litre. If the solutions are more dilute, some precipitation takes place, the quantity of sulphide formed being greater in the case of cobalt than in the case of nickel. The presence

of the precipitated sulphide accelerates the reaction in both cases.

Rise of temperature accelerates precipitation from solutions of cobalt sulphate, but precipitation is not as complete as with nickel sulphate under the same conditions. The precipitation of nickel in fact takes place more readily than the precipitation of cobalt as the acidity of the solution increases. The more concentrated the original solution of the neutral salt, and consequently the greater the quantity of acid liberated during the reaction, the greater is the precipitation of the nickel as compared with that of cobalt. It follows that a smaller quantity of free acid is required to prevent the precipitation. of cobalt than to prevent that of nickel. With weak acids, the difference is still distinct. In a solution containing only a small proportion of free acetic acid, the precipitation is greater in the case of cobalt, but if the proportion of free acid is increased the precipitation of nickel becomes the greater of the two. C. H. B. i

VOL. LIV.