oxidation; it cannot therefore give off any of those unpleasant compounds which more or less are found in the vicinity of all alkali works. It is, moreover, not unreasonable to expect that a matter consisting chiefly of CaO,SO, and CaO may be found useful as a stimulant to various descriptions of soils, and thus the whole of the S used in the soda process in one shape or another may be rendered useful, instead of being a nuisance, as is the case at present.

"The residual products from the bleaching powder works are received into a tank so built that free hydrochloric acid does not destroy the structure. By this means any insoluble portions are separated, and the clear liquid is run off into an adjoining cistern.

"To this acid solution of chloride of manganese and iron is added that of the polysulphide of calcium and the lime compounds of sulphur obtained in the manner previously given. The presence of free hydrochloric acid causes an immediate precipitation of all the sulphur, free from the sulphide of calcium and the accompanying substances containing sulphur; and the addition of the yellow liquor is continued until the first appearance of a black colour, indicative of all the free acid being neutralised, and the first portion of iron from the chlorine residuum commencing to be precipitated. The precipitated sulphur is removed from the liquid, and the greater portion of the accompanying water is separated by pressure. After this the remainder of the moisture is expelled by a very low heat, and the sulphur is then employed for producing sulphuric acid.

"It is obvious from what has preceded that the chlorides of manganese and iron must be left in the solution from which the free hydrochloric acid has just been removed in precipitating the sulphur; and it is in this way that the neutral solutions of these metals are obtained which are required for operating upon subsequent portions of the soda

waste.

"This process has been in operation at Dieuze for some months, and at the present moment by its means about I tons of sulphur are being recovered daily. It will be seen that no new material is required, the only ingredients being

the two waste products from the manufactory itself. The apparatus employed is of a most simple character, consisting almost entirely of tanks, on which the expense for maintenance will be a mere trifle-in fact, the whole cost is one of labour, which at the Dieuze works amounts to something like 40s. per ton on the sulphur obtained.

"Supposing 40 per cent of the sulphur used in this kingdom to be thus recovered, the annual saving this process is capable of effecting will amount to a considerable sum.

"Instead of employing the yellow liquor' and the chloride of manganese in the way set forth in this paper, an attempt has been made at Dieuze to employ both as a means of recovering manganese, a desideratum with bleachingpowder makers as eagerly sought for as the regeneration of sulphur has been with the soda manufacturer. I shall with your permission proceed to describe the process which the owners of the establishment assured me promises to be a

success.

"The acid solutions from the bleaching-powder works, being all required in order to precipitate sulphur by means of the free hydrochloric acid, contain a considerable quantity of neutral chlorides of manganese, and will remain on hand. To such portions of these neutral chlorides as are not used in the sulphur process itself, yellow liquor is added in a suitable tank so long as a black precipitate falls, which is variable in quantity with the varying composition of the manganese used. The black precipitate consists of sulphide of iron and free sulphur, which can be collected and burnt in an ordinary furnace for burning pyrites.

"The iron being thus all separated from the metallic solution, a fresh quantity of yellow liquor is added, by which all the manganese is thrown down, the precipitate consisting of some free sulphur and sulphide of manganese.

"The sulphide of manganese is burnt in the same way as that of iron, but the residue, instead of being all oxide, as is the case when the sulphide of iron is under treatment, is composed of protoxide and binoxide of the metal mixed with a certain quantity of sulphate of manganese. The oxides are separated in the usual way by water, and being almost

chemically pure, are of great value to the glass-makers, to whom the presence of the iron usually found associated with commercial manganese is a subject of great inconvenience.

"The sulphate of manganese, in a concentrated solution, is added to nitrate of soda in quantities denoted by the equivalents. When heated, decomposition takes place; nitrous acid is given off, which may be used in the sulphuric acid chambers, or otherwise disposed of; and the residue. consists of sulphate of soda and the protoxide and binoxide of manganese, which latter represent, so far as available oxygen is concerned, a manganese amounting to 65 to 70 per cent of binoxide. The oxides of manganese are separated from the sulphate of soda in the usual way by washing with water, and both used for any purpose to which these two substances are commonly applied.

"I may add that these operations have been carefully examined by some of the leading men of science in France, both in their practical and scientific relations, and that in the recent adjudication of prizes at the International Exhibition, at Paris, the inventors had a gold medal awarded for the service they are considered to have rendered to the industry of their country."

Spencer produces sulphuretted hydrogen from the residues of the soda manufacture and from lime which has been used for purifying coal gas. This sulphuretted hydrogen gas is made to react upon per- and protoxide of iron, forming sulphide of iron, which is then submitted to a distillation or roasting process.

Great quantities of froth-like sulphur are separated from the mother liquor obtained in the production of iodine in Scotland, owing to the decomposition of polysulphides and hyposulphites.

Though these processes, strictly speaking, are not metallurgical operations, we have not hesitated to give the most important of them in extenso, as their further development

will influence the price of sulphur, and thus indirectly bear upon the extraction of sulphur from its ores.

The chief methods of extracting sulphur from its ores may be classified under the two following divisions.

I. EXTRACTION OF SULPHUR FROM SULPHUROUS

EARTHS.

Very rich earths are melted in pans. In Sicily, Milos, and Spain these ores are liquated in small cupola furnaces after the old Sicilian method. An improved method is now also employed in Sicily, namely, a liquation in mounds. At Radoboi and Swoszowice, the sulphurous earths are distilled in furnaces.

II. EXTRACTION OF SULPHUR FROM IRON PYRITES OR PYRITIC ORES.

At Altsattel and Rosenau these ores are distilled in vessels; they are roasted in cupola furnaces at Johann-Georgenstadt, Breitenbrunn, and Sembirsk; roasted in mounds at Bohemia, Saxony, Salzburg, Steyermark, and Agordo ; and roasted in open heaps at the Lower Hartz and Agordo.

The raw sulphur resulting from either of those methods is then submitted to purification either by re-melting, distilling or subliming.

1. Extraction of Sulphur from Sulphurous Earths.

The following methods of extraction are used according to the richness of the ores and the prices of fuel and sulphur.

1. Smelting very Rich Ores in Pans.-The richest pulverulent Sicilian sulphurous earths are melted in cast-iron pans with a capacity of about 2 cubic metres. The ores are gradually charged whilst stirring till the pans are filled, when the gangue is removed from the liquid mass. The temperature must be kept a few degrees above the fusionpoint of the sulphur so as to render the sulphur as liquid as water without igniting it, and to allow a perfect separation of the earthy substances at the bottom of the pan and on the surface of the fused mass. Having allowed the whole to settle, the froth formed on the surface is skimmed off, and the clarified sulphur ladled into iron boxes, allowing the deposit

at the bottom of the pan to remain till after several meltings. The cold sulphur is broken into pieces and sold as raw sulphur. The melting of one charge in pans with a capacity of 2 cubic metres takes from 6 to 8 hours, the clarification of the mass 12 hours, and the ladling out 2 hours, consuming an amount of wood equal in weight to 10 per cent of the ore treated. The removed gangue retains about 30 per cent of sulphur, and the deposits on the bottom more than 40 per cent. Both are thrown away. The richness of the residues. prevents the treatment of poor ores by this method.

2. Liquation of the Sulphur in Apparatus (Cupola furnaces or covered heaps) with a greater or smaller admission of air, thus burning part of the sulphur in producing the temperature required for liquation. The Sicilian furnaces (calcarelle) cause a greater loss of sulphurous acid (20 per cent of sulphur and more) than the covered heaps (calcaroni), owing to a too speedy combustion. The covered heaps may be placed in the immediate vicinity of dwelling houses and cultivated fields, whilst the older furnaces had to stand some thousands of feet from them and were in operation only in a certain season of the year; working in covered heaps is also less injurious to the health of the workmen. Since 1860, Hill has tried to avoid the noxious influence of the sulphurous acid by melting the ores in high cylindrical furnaces, directing the combustion gases of coal through the furnaces.

Poor and moderately rich sulphurous earths were formerly liquated in Sicily in cylindrical furnaces 6 or 7 feet wide and 4 or 5 feet high, the sole of the furnace being somewhat inclined, and furnished with an open channel for igniting the ores and removing the residues. The furnace had also several openings for admitting air, and one for tapping off the liquated sulphur. The larger pieces of ore were placed inside round the periphery of the furnace, upon a small projecting rim, then a sort of vault was formed of smaller pieces with a small opening at its apex, and upon this still smaller pieces of ore were placed, and lastly covered with ore dust, the whole forming a pyramid. A lining of turf, 7 or 8 inches broad, was placed round the basis of the pyramid, which was covered with straw; by igniting the straw the