From concentrated solutions of strontium chloride and dihydrogen sodium pyrophosphate, a slight flocculent precipitate of the composition 2Sr,P207,H2SrP2O, + 6H2O is obtained; from dilute solutions, a crystalline precipitate separates of the formula 3Sr2P2O7,SrH2P2O1 + 2H2O, whilst if the solution is heated to boiling, the salt

is formed.

3Sr2P2O, SrH2P2O, + H2O

Solutions of barium chloride and dihydrogen sodium pyrophosphate when mixed in the cold yield the white crystalline salt

:

A. J. G.

Action of Arsenious Trisulphide on Iodine. By R. SCHNeider (J. pr. Chem. [2], 36, 498–515).—A solution of iodine in carbon bisulphide is without action on natural arsenious trisulphide (orpiment), but reacts with that precipitated by hydrogen sulphide, forming arsenious iodide and sulphur. Attempts to prepare the compound As S3,2ASI, by heating a mixture of iodine and arsenious trisulphide in the ratio As2S, 61, were not successful. The mixture fused at a low temperature to a homogeneous mass of a brown colour, which dissolved almost entirely in carbon bisulphide; on evaporation of the solvent nothing but arsenious iodide and sulphur crystallised out. On distilling a mixture of arsenious trisulphide and iodine in the ratio As S3: 6I until two-thirds of the material had passed over, the distillate was found to contain 58 63 per cent. of free iodine, 40 per cent. of arsenious iodide, and 1·37 per cent. of sulphur; the residue consisted of 55.32 per cent. of arsenious trisulphide and 44:04 per cent. of arsenious iodide. When in place of the former, a mixture of arsenious iodide and sulphur in the ratio of 2AsI, 3S was employed, and the distillation continued until half the material had passed over, the distillate contained 69.44 per cent. of free iodine, 28 per cent. of arsenious iodide, and 2.56 per cent. of sulphur. These experiments show that whilst a mixture of arsenious trisulphide and iodine is converted at moderate temperatures into arsenious iodide and sulphur, these products again react at higher temperatures, reproducing their generators. If the distillate, rich in iodine, is sealed up in a glass tube, which is slightly inclined so that the distillate occupies the higher portion of the tube, and gently heated in a water-bath to a temperature of about 72°, a dark-brown liquid which solidifies on cooling trickles to the bottom of the tube. By repeated liquations in sealed tubes this dark-brown mass becomes perfectly homogeneous, crystallising in hard, brittle plates of a greyish-black colour, and dull lustre. The pure substance melts at 72°, and is represented by the formula SI,2As I3. On pulverising, it forms a reddish-brown powder which by exposure to the air rapidly loses iodine, whilst the residue, consisting of a mixture of arsenious iodide and sulphur, assumes a bright-red colour.

:

On fusing a mixture of arsenious trisulphide with iodine in the ratio As2S, 41, the iodine reacts with only two-thirds of the arsenious trisulphide present. When, as not infrequently happens, the arsenious trisulphide contains arsenious acid, there remains behind, after fusion

with iodine and treatment with carbon bisulphide, an insoluble paleyellow powder of the formula 2As,S,,3(Asl,, As,O,). This substance can also be prepared by heating a mixture of arsenious trisulphide (1 part) and arsenious iodide (0.2 part) with a large excess (8 to 10 parts) of arsenious iodide, or by heating a mixture of arsenious iodide (4 mols.) with arsenious trisulphide (1 mol.) with free access of air. Under the microscope, the compound appears to be indistinctly crystalline. On gently heating it, arsenious iodide first sublimes, then arsenious acid, and lastly arsenious trisulphide.. The compound is completely dissolved by solutions of potash and ammonia, and is readily decomposed by the common mineral acids and by boiling G. T. M.

water.

Silicon. By H. W. WARREN (Chem. News, 57, 54).-The following is a new method of preparing silicon. Small bars of "silicon-eisen are suspended in dilute sulphuric acid from the positive pole of a battery of two ferric chloride cells and are in contact with a platinum plate forming the negative pole. The iron dissolves and leaves a residue of graphite, silica, and amorphous silicon, which is heated to redness. in a stream of carbonic anhydride, and then to a full red heat in a closed iron tube with some zinc; the zinc button obtained in this manner is dissolved in hydrochloric acid, when crystalline silicon remains undissolved; by heating the amorphous silicon at a full white heat with aluminium instead of zinc, graphitoïdal silicon is obtained. When an alloy of aluminium and silver is heated to an intense white heat with potassium silicofluoride, small quantities of silicon are produced in the form of a bright reddish-brown powder. D. A. L.

Silver Suboxide and the Action of Potassium Permanganate on Silver. By C. FRIEDHEIM (Ber., 21, 307-318).-The first part of this paper is devoted to a criticism of v. d. Pfordten's latest communication on this subject (this vol., p. 221), and, in particular, attention is drawn to the fact that he no longer insists that the substance in question is silver suboxide, but only that it is not metallic silver. Referring to the statement that silver is dissolved by water acidified with sulphuric acid and exposed to the air, the author again states that the metal could not be detected in the solutions at the end of each experiment (compare Abstr., 1887, 1079). The action of permanganate has been studied under new conditions in an apparatus so contrived that a solution of permanganate acidified with dilute sulphuric acid placed in one bulb could by means of a connecting tube be brought in contact with a silver mirror in a second bulb after the bulbs and contents had been heated at 50° and at 100° respectively for 4 to 5 hours, whilst the apparatus was connected to a TöplerHagen's mercury pump, and then allowed to cool. Various strengths of permanganate were used, and in one experiment spongy silver was employed, but the results in every case showed that the permanganate acted at once on the silver and completely dissolved it. Experiments with the acidified permanganate solution per se showed that, on boiling. a decomposition occurred with the separation of an ochre-yellow or black oxide of manganese according to the concentration of the

solution, and that this decomposition also occurred, although to a much smaller extent when the solution was heated at 40-50° for 4 to 5 hours in a vacuum. On this account, v. d. Pfordten's experiment of treating silver with a boiling acidified permanganate solution in a current of carbonic anhydride was not repeated, but in its stead the experiment in a vacuum was modified to the extent of filling the cold vacuous apparatus with pure carbonic anhydride (free from air) under pressure; connection was then made between the bulbs, with the result that the silver dissolved as before.

In reply to other objections to the author's views (loc. cit.) raised by v. d. Pfordten, it is pointed out that the complete dissolution of the latter's preparation (before ignition) in nitric acid does not disprove the presence of organic matter, since many organic substances are completely soluble in nitric acid. Again, the statement that no case is known in which impurity in the silver hinders amalgamation is met by an experiment in which an intimate mixture of finely divided silver and magnesia, obtained by adding calcined magnesia to a neutral solution of silver nitrate and igniting the precipitate, was shaken continuously with mercury for eight hours with the result that 1.149 gram of silver was dissolved and 0.8322 gram remained in the residue; hence v. d. Pfordten's argument, based on the fact that his substance underwent no change when shaken with mercury, is open to criticism. Finally, the change of colour from black to grey occurring when the so-called suboxide is treated with sulphuric acid or solutions of indifferent salts (Ber., 20, 1470, 3379) is paralleled by a similar change under like conditions in the colour of metallic silver precipitated from an ammoniacal solution of silver chloride by zinc, or from neutral silver solutions by other metals (Vogel, Ber. Berl. Akad., 1862, 289). On these grounds, and without contesting the question of the existence of silver suboxide, the author maintains that v. d. Pfordteu's substance is not this compound, but a mixture of finely divided silver with more or less silver oxide or organic matter. W. P. W.

Lead Slags. By M. W. ILES (Chem. News, 67, 4-7, 18-19, 37— 38, 43-45, 57-58).-This communication contains the results obtained, and observations made in a very extensive investigation into the character and composition of lead slags. The sp. gr. of lead slags varies from 33 to 4:16, the best slags having a density of 34 to 365. Iron, barium, and lead cause high sp. gr.; aluminum, silica, and lime low gravities. All good slags are as a rule more or less perfectly crystalline; slow cooling favours crystallisation, sudden cooling impedes crystallisation or even stops it altogether, hence the crusts of pots of slag are devoid of crystalline structure. Well-crystallised slags have definite fusing points, and are more brittle than the imperfectly cry-talline slags, and are only partially soluble in strong acids; the form of crystallisation serving as an important indication of the quality of a lead slag. Slags cooled by pouring into water are amorphous, have their fusing point lowered, resemble obsidian in appearance, and when pulverised are completely dissolved by hydrochloric acid. The author takes advantage of this property in taking and preparing samples for analysis; the crust of the pot of slag is thrown aside, a steel bar is

thrust about 2 inches deep into the molten slag and then plunged into water. The outside rims of pots of slag are subject to rapid cooling. The colour of lead slags is almost always black or a dark shade. Lustrous black and the darkest slags contain most iron, this element, however, sometimes imparts a reddish tint, sometimes a slight greenish cast; lime tends to lighten the colour, giving the slag a stony or earthy appearance; large quantities of manganese give a reddish to amethystine hue, and when associated with 20 per cent. or more of lime, the slag has very often a resinous colour. Zinc in the presence of alumina, manganese, and much silica produces a porcelain or obsidianlike slag, whilst some very siliceous slags have a greenish cast. The lustre of lead slags is rarely pearly, often resinous, submetallic splendent, and pitchy; most are vitreous with the exception of high iron and high lime slags.

Both very viscid and very fluid slags are undesirable, inasmuch as the former retain globules of matte and metal, whilst the latter do not come sufficiently in contact with the ore, especially if it is in somewhat coarse lumps. Silica is the great cause of viscosity, whilst iron and manganese increase the fluidity of a slag, but fluidity due wholly to iron is liable to cause an iron crust, and so occasion loss. Lime may or may not make a fluid slag, most high lime slags, however, flow smoothly. Fusibility is a very important property of a slag. and is increased by iron, manganese, lime, and by alumina if the silica is low, and rarely or never by manganese and zinc. It is diminished by silica and by alumina in presence of much silica. Refractory slags arise either from insufficient temperature or from injudicious combination of the charges. The closer certain recognised types are approached, the greater will be both the fusibility and fluidity of a slag. Increasing the number of elements in a slag generally makes it more fusible, hence mixing different ores is advantageous; this remark, however, does not apply to zinc, aluminium, and magnesium: the latter element for some unaccountable reason occasions great loss of silver.

All lead slags are magnetic, the author attributing this property to the presence of iron silicates and sulphides. The brittleness of these slags depends on the number, kind, and amount of the bases present; generally silica causes toughness, and bases brittleness, although the latter is not always true. Slags with less than 34 per cent. of silica are usually brittle, whilst those containing as much as 35 to 40 per cent. are tough, unless there is little iron and much lime (22 to 30 per cent.). Whenever there is much matte produced or when zinc is present in the ore, it is best not to have very brittle slags. Brittle slags are generally free from both silver and lead. Lead slags consist mainly of iron and calcium silicates, manganese, however, is frequently present, so are also zinc, aluminium, barium, and magnesium, but the last four are to be avoided as much as possible. Incidental constituents of lead slags are silver, lead, potassium, sodium, phosphorus, sulphur, sometimes copper, nickel, and cobalt; whilst Leadville slags frequently contain vanadium. In abnormal slags, quartz, ferric oxide, and quicklime are sometimes found. Delicate needles containing lead and sulphur are observed in the blistered cavities in the crust of pots of slags.

The author does not approve of decomposing the slags by fusion with sodium carbonate and nitrate in a platinum crucible, but if such a method is resorted to, the pulverised slag should be first treated with hydrochloric acid, evaporated to dryness, more hydrochloric acid added, filtered, and then fused with sodium carbonate; or, better, fuse the slag directly with potash in a silver crucible, or if silver is also to be determined, in a platinum crucible heavily plated with gold. The method generally followed by the author is to take the sample in the way already noted, pulverise and moisten about half a gram with water, add concentrated hydrochloric acid, and digest with a few drops of nitric acid, the silica can then be separated perfectly free from iron in the usual manner. Iron is determined by permanganate, calcium as oxalate or volumetrically, manganese by the bromine or zinc oxide methods, other constituents by the usual methods.

The success of smelting siliceous ores depends on the economic use of lime, iron, and manganese as fluxes, whilst the life or campaign of a furnace is greatly influenced by the judicious selection of slags; such inconveniences as the accumulation of silica, or iron, charcoal, coke, zinc, or lead crusts may be eliminated by the use of suitable slags for some time. Slags must of course be varied to suit the impurities in the ores to be dealt with, but from the author's experience and the careful and complete analyses of 100 slag samples, the results of which are given in a table, it is concluded that certain definite "slag types," or slags having some well-defined composition and a distinct crystalline form exist, and that the nearer slags in general approach to any of these types the more effectual they are. Taking the important constituents lime, iron and manganese, and silica, it is observed that the best slags range within the following limits per cent.: SiO2 31 to 36, Fe + Mn 23 to 30, CaO 14 to 25: whilst the slags doing the best work and ensuring the longest campaigns do not vary beyond SiO, 31 to 34, Fe+Mn 24 to 27, CaO 14 to 25. The limits SiO2 26 to 41, Fe + Mn 18 to 35, CaO 5 to 35, would include all lead slags.

The seven types laid down by the author include practically every known slag which is well adapted for melting argentiferous lead, and are composed as follows as regards the most important constituents:

Type A. Crystallises in rectangular plates; but is not adapted to lead melting as the iron is too high, the lime too low. Type B. Forms generally small, rhombic plates more or less thickened and characterised by well-defined striations. This type of slag will keep the furnaces in good condition, it gives large yields, but is liable to cause large losses of lead and silver; it is not a bad slag in localities where limestone is dear. Type C. Is black and distinctly crystalline, and has the formula 6FeO,3SiO2 + 2CaO,SiO2 assigned it. It is highly recom