a longer time and rapidly cooled, it shows the phenomenon of spitting. Platinum does not fuse in a porcelain furnace, but, according to Aubel,* it does in Rachett's iron blast furnaces. Richter and Heräus† doubt this, and explain it by the formation of more easily fusible combinations of platinum with either carbon or silicium. Heräus suggests that the spitting of platinum only takes place if oxygen is admitted under too great a pressure.

2. Smelting of Platinum Ores with Galena.-Equal parts of platinum ore and galena are fused in a reverberatory furnace, and continually stirred until a lead matt has been formed with the iron contained in the platinum ore, and till the platinum has alloyed with the separated lead. Some difficultly fusible glass is now added, the temperature raised, and litharge is gradually added to decompose the matt. When no more sulphurous acid is emitted, the metal bath is allowed to settle for some time, depositing osm-iridium; the plumbiferous slag is tapped off, and the plumbiferous platinum ladled out. The residue is reserved for the next smelting until it is sufficiently rich in osm-iridium. The plumbiferous platinum is then cupelled and refined in the lime furnace.

3. Production of pure Platinum by combined Wet and Dry Processes.-The ore is dissolved in aqua regia, the chlorides decomposed by heating, the reduced platinum separated from the undecomposed chlorides by washing, the platinum is boiled with nitric acid, and then refined in the lime furnace. The washed out substances are heated with sulphuric acid to extract iron, copper, and part of the palladium, and the remaining oxides of rhodium and iridium are washed, dried, and reduced in a crucible.

In 1862, about 50 cwts. of raw platinum were produced in Russia.

B. u. h. Ztg., 1862, p. 392; 1863, p. 272.

↑ Ibid., 1863, pp. 195, 256.

Ibid., 1862, p. 419; 1864, pp. 329, 341.

CHAPTER XIII.

SULPHUR.

PRINCIPAL SULPHUR ores.

SULPHUR is produced from the following ores and sub

stances:

I. Native Sulphur.-Sulphur is found native in three different forms-Ist, in kidney-shaped lumps, disseminated through layers of tertiary or contemporaneous formations; 2nd, in irregular masses in chalky formations, associated with gypsum and rock salt; it is principally found in this condition in the mines of Sicily, which supply nearly all the commercial sulphur in Europe; 3rd, as a sublimate round the mouths of volcanoes, where it is mixed with the ashes or sand; the solfataras of Guadaloupe and Pouzzales supply it in this state.

The principal sulphur mines of Sicily are situated near Cattolica, Girgenti, Licata, Caltanisetta, Caltascibetta, Centorbi, and Sommatino.

Sulphur in admixture with different minerals is called sulphurous earth.

2. Metallic Sulphides, chiefly iron pyrites, FeS2, containing 53'33 per cent of sulphur; and copper pyrites, Cu2S, Fe,S,, containing 34'89 per cent of sulphur.

3. Artificial Products, such as the residues of the manufacture of soda, which contain oxysulphide of calcium, and allow of the extraction of the sulphur in an indirect way.

SYNOPSIS OF PROCESSES FOR THE EXTRACTION OF SULPHUR FROM ITS ORES.

According to the richness of the ores, these processes are based either upon a liquation process, when the ores are very rich, or upon a heating of the ores, and expelling the sulphur in the form of a vapour, which is collected and condensed (distilling process). The sulphur produced by the liquation process contains more mechanical admixtures than the distilled sulphur. Sulphur forms a thin fluid at 112o C., and solidifies at 108° or 109° C.; it is a thick fluid of a darker colour at 140° C, and it forms a pasty mass scarcely fusible at 220° C. When heated up to 340° its mobility decreases, and its volatilisation commences at from 420° to 440°, when it is almost black.

The apparatus used for the distillation of the sulphur varies in different establishments. Closed vessels (tubes of iron or clay) are sometimes used, which must be heated by a separate firing. Open heaps or cupola furnaces are made use of in other works, and then the temperature required for distillation is produced by burning part of the sulphur.

The choice between the different methods chiefly depends on the prices of fuel, sulphur, and labour.

As the expulsion of the last portions of sulphur from pyrites necessitates a higher temperature than is required at the commencement of the process, and as the higher temperature attacks the distilling vessels more strongly, a large yield is always abandoned in order to save fuel. Iron pyrites may yield 23 per cent of sulphur when heated so as to form magnetic pyrites

7FeS2 = 6S+6FeS, FeS2;

but the smelting works do not usually produce more than 15 or 18 per cent. Copper pyrites, Cu2S, Fe,S,, yields 9 per cent of sulphur, being ultimately transformed into Cu2S,2FeS.

The raw sulphur obtained by the liquation or distillationprocess contains mechanical admixtures of ore, and sometimes arsenic and selenium in chemical combination.

According to Phipson,* sulphur from the Solfatara, Naples, contained 87.6 per cent of sulphur, 11*162 per cent of arsenic, and 0 264 per cent of selenium.

Only the mechanical admixtures are separated by refining the sulphur, either by a re-melting or a subliming. The sulphur produced from pyrites is still more impure than that extracted from sulphurous earths. It is said that the common English brimstone, such as was extracted from the copper pyrites of the Parys mine in Anglesea, contained fully a fifteenth of residue, chiefly orpiment, insoluble in boiling oil of turpentine. The residues of the extraction of sulphur from sulphurous earths are thrown away; those from iron pyrites are used for the production of sulphate of iron and alum; and if they contain valuable metals, such as copper, silver, or lead, the residues are submitted to suitable processes for extracting these metals.

For extracting sulphur from the residues of the soda manufacture, different methods have been recommended, some of which have been brought to great perfection. Gossage, Favre, and Noble treat the residues with the muriatic acid resulting as by-product from the soda manufacture, producing sulphuretted hydrogen gas, which is then decomposed by sulphurous acid, forming sulphur and pentathionic acid:5S+S,O,+5HO;

5SO2+ 5HS

2

=

this entails a great loss of sulphur.

Three different methods have been patented in England, as follows:-L. Mond, 8th September, 1863; M. Schaffner, 23rd September, 1865; P. W. Hofmann, 9th April, 1866. These processes are all based on the same principle, viz., the conversion of the insoluble sulphide of calcium in the waste into soluble compounds by bringing the waste into contact with air in order to oxidise it; the lixiviation of the oxidised mass; and the precipitation of the sulphur in these liquors by a strong acid,-in practice muriatic acid. Though it is only within the last few years that sulphur has for the first time been regularly manufactured from alkali waste by Mr. Mond's process, the progress of

this new industry has advanced so rapidly that, at the Paris Exhibition of 1867, no less than seven works exhibited sulphur recovered from waste by the methods patented in England.

Mr. Ludwig Mond* describes this important process as follows:

"Alkali waste, black ash waste, tank, vat, or blue waste, are the different names of the insoluble residue obtained by the lixiviation of artificial crude soda, or black ash, produced by Leblanc's celebrated process for the manufacture of alkali. Every ton of alkali produces no less than 1 tons of dry waste, and this waste has been always regarded as the greatest drawback to this important manufacture. The enormous quantities of waste thus obtained are generally deposited in the neighbourhood of the works, often forming hills of considerable height. In damp weather especially this waste evolves large quantities of sulphuretted hydrogen, that most noxious and most disagreeable of all gases, greatly annoying the surrounding population; and, moreover, the rain and ground-water coming into contact with it dissolve out considerable quantities of yellow liquor, containing hydrosulphide and polysulphide of calcium, which poisons the water of all wells and rivers to which it has access. These evil results are altogether due to the sulphur contained in the waste, which amounts to no less than 80 per cent of all the sulphur used in the manufacture of alkali, and which represents, of course, a very considerable value.

"In 1852, W. S. Losh took out a patent for obtaining hyposulphite of soda by exposing waste in heaps to the atmosphere, lixiviating it, adding carbonate of soda to the liquor, and crystallising."

Mr. Mond now makes the further statements :

"Being engaged in researches on the different processes for sulphur recovery by Mr. Gossage and others, in the summer of 1860, my attention was drawn to Mr. Losh's patent, and I at once started a series of experiments in order to ascertain whether, and under what conditions, a quantity of hyposulphite of lime could be obtained by oxidation + Chemical News, 1867, No. 398, 399.