may exist or result, is that of heating the dry impure soda with sawdust, or with ground coal or charcoal, in a reverberatory furnace, but not to a heat exceeding 700° F., frequently turning and stirring the mixture, until the burning jets of carbonic oxide from it cease; after which the mass is to be again leached, and the lixivium evaporated. In the more expeditious process of Gossage, the sulphide of sodium is decomposed by a hydrated oxide, as of lead, giving caustic soda, which is carbonated by passing carbonic acid into the solution, and sulphide of lead, which is precipitated. The precipitate removed, its decomposition is effected by chlorhydric acid, giving sulphydric acid, which is burned for sulphuric acid, and chloride of lead, which by means of lime is restored to the hydrated oxide for re-use.

Other methods of obtaining a comparatively pure monocarbonate of soda (NaO.CO2) are also in use. For removing ordinary impurities, of course, the lixiviation of the alkali may be once or more repeated. The conversion of the monocarbonate into the bicarbonate (NaO. CO, HO.CO) is effected either by passing into a solution of the former a stream of carbonic acid, or by exposing the crystallized monocarbonate to the action of carbonic acid gas. In the method of Schlösing and Rolland, common salt being at the outset dissolved in water, ammonia and carbonic acid are successively added, with production at first of bicarbonate of ammonia, and then (by reaction) of bicarbonate of soda and chloride of ammonium. The former can, if desired, be reduced to the monocarbonate by heating. The chloride of ammonium being boiled with lime, the ammonia is re-formed for use again. Finally, when the hydrated or caustic soda is the article desired, this is readily obtained by treating a solution of the monocarbonate with milk of lime, the resulting carbonate of lime separating by precipitation.

Theory of Leblanc's Process.-This process has of late been discussed from a theoretical point of view by different writers, among them especially by M. J. Kolb and by M. Pelouze. M. Kolb considers that, in a heated mixture of one equivalent of sulphate of soda, one equivalent of chalk, and three equivalents of carbon, in an atmosphere of carbonic acid, the following reactions take place, and in a manner simultaneously:

NaO.SO3+20=2CO2+NaS;

CaO.CO, + C = 2CO (burnt in furnace) + CaO;

NaS+CaO+CO. (in excess) NaO.CO2+

CaS.

=

The proportions here given correspond to sulphate of soda 100 parts, carbonate of lime 70.4, and carbon 25.5 parts, by weight; and theoretically the mixture should yield 74.6 parts of monocarbonate of soda. In reality, however, it will commonly yield only about 62 parts, in carbonate and hydrate of soda, the causes being such as that of imperfect mixing, loss of some carbon

by burning, failure to maintain the proper temperature, etc. The author judges that the best practicable yield of soda is obtained when the proportions of sulphate, chalk, and carbon are 100, 94, and 44, the yield then being of carbonate of soda 64.20, and of caustic soda 4.72 parts, the whole equivalent (when the latter has been carbonated) to 72.2 parts of carbonate of soda. He thinks, however, the excess of chalk and charcoal a difficult matter to state generally-that it must be left to the discretion of the manufacturer, and will depend in a measure on the form of his furnace, the method of stirring, and other points.—Chem. News, March 23, 1866, from Ann. de Chim., etc., February, 1866.

In another paper, M. Kolb argues also, consistently with his view of the reactions above given, and at variance with the theory of the change previously presented from Ure, that the carbonic acid of the chalk does not contribute to the formation of the carbonate of soda, but that it is especially from the gases of the furnace [referring doubtless in part at least to the carbonic acid generated by burning of the oxide of carbon] that the final reaction results: NaS, CaO, and CO, then resulting in NaO.CO, and CaS. The author considers the action, respectively, of dry air, of moist air, and of water, on the rough or crude soda. He finds that from 0° to 100° C., perfectly dry air exerts no sensible action on crude soda, not even by its carbonic acid; but that somewhat below and at a red heat, dry air oxidizes some sulphide of calcium into sulphate of lime, which then lowers in a degree the alkalimetric richness of the lixivium. Moist air acts very energetically, some lime present being hydrated and then carbonated, while part of the still remaining sulphide of sodium is transformed into sulphate of soda, either directly or through intervention of the oxide of iron present here [it would appear, referring to soda obtained by Kopp's process], and which keeps up the transformation by being indefinitely regenerated. The action of water on crude soda is to give a lixivium of varying composition, depending on these conditions-the concentration of the liquid, the duration of the digestion, and the elevation of the temperature. The last two of these favor the caustifying of part of the earbonate of soda by lime, and a slow, and of course wasteful, reaction between the carbonate of soda and sulphide of calcium. The firstnamed condition, and the presence of caustic soda, as also of lime, oppose this last formation. A little fresh lime would then seem desirable in rough sodas, as having the effect of producing small quantities of caustic soda, and thus opposing an obstacle to the sulphuration of the lixivium. (Chem. News, April 6; 1866, from Compt. Rend., lxii., 638.) A more full disens sion of the topics here considered, and with tabular statements, is commenced in the Chem. News, July 13, 1866, vol. xiv., p. 16, an abstract from Ann. de Chim., etc., June, 1866.

In respect to the chemical character of the mainly insoluble residues existing along with soda in the crude ball alkali, M. Scheurer-Kestner has very recently declared that his analyses do not show in those residues the presence of an oxysulphide of calcium, but rather of varying proportions of oxide, carbonate, and sulphide of calcium, depending, as he implies, on the proportions of the chalk and sulphate ased in the manufacture. Pelouze, Gossage, Kynaston, and others agree in this opinion, that the sulphur of the residues is not present in an oxysulphide.

M. Pelouze expresses, at the close of a paper on the theory of Leblanc's process, before the Academy of Sciences, February 12, 1866, the following as the conclusions to which his analyses and his study of the subject lead:

1. That "black ash" is a mixture of carbonate of soda, sulphide of calcium, carbonate of lime, and free lime.

2. The ash, on prolonged contact with water, hot or cold, gives an amount of caustic soda proportional to the free lime the ash contains, and then the lime in the waste is completely neutralized by sulphydric or carbonic acid.

3. This reaction with the carbonate of soda not usually being complete, the waste will commonly contain some free lime.

4. Any black ash being given, free lime may be left in the waste, or not, just as the lixiviation is managed.

5. Nothing has yet demonstrated the existence of an oxysulphide of calcium, nor of any other compound of lime with sulphide of calcium.

(Chem. News, February 23, 1866.)

M. Verstraet details at length, in Le Technologiste for April, 1865, a convenient method of testing accurately the quantity of sulphide of sodium present in a lye of crude soda.

Other Processes with Sulphate of Soda.Among the modifications of Leblanc's sodaprocess, at least in its first stage, and which have been to some extent brought into successful practice, are those of obtaining the sulphate of soda by heating green vitriol (sulphate of iron) with common salt, the chloride of iron, which simultaneously forms, being volatilized; and of roasting, with common salt, copper or iron pyrites-the latter affording a means of using ores otherwise too poor to be worked with profit. (Ure.)

In the method devised by M. E. F. Anthon, of Prague, equivalent quantities of marine salt, gypsum (sulphate of lime), and calcined magnesia are mixed with a quantity of water of six or eight times the weight of the salt, a current of carbonic acid is introduced and the mixture kept agitated: carbonate of magnesia forms, reacting with gypsum to produce carbonate of lime and sulphate of magnesia, the latter of which reacting in turn with the common salt, gives sulphate of soda and chloride of magnesium. The lime-salt precipitates, and the liquid being properly evaporated, the sulphate of soda crystallizes, while the chloride of magnesium remains

Mr. A. G. Hunter, England, patented in April, 1865, a method of converting sulphate of soda or potassa into the corresponding carbonate, by boiling under pressure (hydraulic, steam, or mechanical) a mixture of caustic lime, in form of milk of lime, with a weak solution of the sulphate of the alkali

in case of sulphate of soda, specific gravity 1.1, and pressure 40 to 50 lbs. to the square inch. When caustic alkali has resulted, the sulphate of lime, insoluble, may be separated by filtration, still under pressure, to be sold as a fertilizer, or purified for special uses. Methods of carbonating the alkali are also given.-Newton's Lond. Jour., April, 1866.

The methods of Macfarlane and Kopp, next to be considered, also involve the use or production of sulphate of soda.

Preparation of Soda, Chlorine, and Sulphuric and Chlorhydric Acids.-In this process, described by Mr. T. Macfarlane in the Canadian Naturalist (February, 1863), sea-salt is decomposed, with fabrication of the substances named. Green vitriol, dried and mixed with sea-salt, is heated to redness in a current of air, with formation of a sesquichloride of iron, and then of peroxide (sesquioxide) of iron and free chlorine: the solid residue consists of the last-named peroxide with sulphate of soda. The reaction is facilitated by previous admixture of some peroxide of iron.

In carrying out the process, 828 parts of green vitriol, dried and partly peroxidized at a gentle heat, are intimately mixed with 352 parts of sea-salt and 78 of peroxide of iron; and the whole is then heated to low redness in a muffle calcining furnace, through which a current of air dried by passing over quicklime is maintained, the mixture being stirred, and the heat kept so low as not to sublime any chloride of iron. The decomposition of the chloride of sodium is stated to be complete, the muffle containing a mixture of peroxide of iron and sulphate of soda, and the chlorine gas given off, though mixed with nitrogen, being available for the preparation of bleaching salts, etc. The solid residue is ground, mixed with 144 parts of coal, and heated to fusion in a reverberatory furnace, the hearth of the latter being prepared substantially of quicklime mixed with a little basic slag or glass, and saturated with sulphide of sodium, The fused mass, treated after cooling with water, yields sulphide of iron, and an impure caustic soda from which more of the same sulphide is precipitated by carbonic acid: the remaining solution of carbonate of soda and caustic soda is to be treated by the ordinary methods.

The sulphide of iron residue from the process is washed, and exposed moist to the action of the air: by action subsequently of water, sulphate of iron is dissolved from the mass, and peroxide of iron separated; and the former being obtained dry, these two materials are available in operating on a new portion of salt.

The chlorine gas evolved being passed, along with an equivalent proportion of sulphurous acid gas (from burning sulphur or pyrites) and with steam, through a condenser filled with coke, chlorhydric and sulphuric acids at the same time result; and these are afterward separated by distillation.—Amer. Jour. of Science, vol. xxxvi., September, 1863.

Kopp's Soda-Process, with Peroxide of Iron. -In the year 1777, M. Malherbe, a Benedictine monk, proposed a method of producing carbonate of soda by acting on the sulphate of the same base by means of charcoal and iron. This process has in its essential features been revived more recently by M. Emile Kopp, of Strasburg, and has been brought into practice at least in some English manufactories. In its present form it consists substantially in decomposing the sulphate of soda by a mixture of carbon and peroxide of iron, the three materials being in the proportion of 125, 55, and 80 kilogrammes, calcining the mixtures, and following with "délitation" (exposure to air and moisture), and finally, lixiviation. With an impure sulphate, the other ingredients should be proportioned to the quantity of pure dry sulphate of soda present. The peroxide of iron should be as pure as may be, weighed dry, and in fine powder; or it may be replaced with carbonate of iron (spathic iron), or magnetic oxide or iron-filings, provided the proportion of iron present in any case be such as to form a sulphide (FCS) with all the sulphur of the sulphate. The mass is best calcined by using a furnace with two or three stories: when in the last and hottest of these it has softened, giving off a yellow flame, and becoming homogeneous, it is drawn off, still red, into boxes on wheels, and solidifies to a black, porous mass. In this condition it is not well acted on by water; but the blocks, being exposed to air and moisture under a shed, rapidly absorb oxygen, water, and carbonic acid, and in course of some hours fall to a pulverulent, reddish mass-a change which M. Kopp sometimes aids by another, termed by him "carbonation." Pulverizing the crumbled mass fine, a grayish powder is obtained, and which is then sifted.

1

The lixiviation is rapid, being performed either by filtration or decantation, and with water at from 30° to 40° C. Crystallization occurs in 24 to 48 hours, without concentration -[the product being a highly pure carbonate of soda]. The residue, again filtered and dried, burns below 100° C., its sulphur being utilized in the production of sulphuric acid, and peroxide of iron regenerated and used again. The latter, indeed, gradually becomes impure, and must finally be replaced by fresh oxide. The sulphur, however, converted into acid, and made to act on fresh portions of salt, is re-used indefinitely. Amer. Jour. of Science, vol. xxi., January, 1856.

Soda-Processes with Baryta, and its Salts.In the same number of the Technologiste (December, 1864) with his article previously

quoted, M. R. Wagner has another paper, and of some length, on the processes for soda specially involving the use of caustic baryta or certain baryta-salts. Of these, the most successful appears to be that by decomposition of sulphate of soda by caustic baryta, patented in England by Fuller in 1819, and by Samuel in 1838, and later recommended on the Continent by M. Anthon, of Prague, in 1840, and by M. G. Hoffacker, of Stuttgard, in 1863. The author states that in his own experiments he has effected an easy and complete decomposition of sulphate of soda by caustic baryta, and that at all degrees of concentration and of temperature; and he is led to coincide in the opinion recently expressed by Prof. Hofmann, that a cheap and plentiful supply of baryta, could this base be so produced, would work a revolution in the business of fabricating soda.

Soda-Processes by Direct Action on Common Salt. In regard to these, little needs be said in this place. In the process of Mr. Samuel, a concentrated solution of sea-salt is treated with excess of oxalic acid, the results being chlorhydric acid and an insoluble binoxalate of soda; and on boiling the latter with milk of lime, caustic soda and oxalate of lime are obtained. The chief difficulty hitherto has been in the want of an economical mode of recovering the acid, for re-use, from the lime-salt.

Propositions have been at several times made, looking to a decomposition of common salt by steam at high temperatures (of course, under pressure, in strong vessels); but the resulting caustic soda and chlorhydric acid tend to decompose again at lower temperatures, and before the soda can be separated, with reproduction of the original materials. The introduction of a third body such as will at once combine with the soda forming, and in a non-volatile compound afterward readily decomposable, offers a means of overcoming the difficulty referred to; and for such purpose alumina and silica have been used.

In Mr. Tilghman's process, precipitated alumina is made up into balls with chloride of sodium; and these are exposed to a current of steam in a reverberatory furnace, strongly heated. Chlorhydric acid and soda result; the former is expelled, and the latter combines with the alumina, from which, when cold, it is again separated by means of a current of carbonic acid: the carbonate of soda is dissolved out, and the alumina can be re-used. (URE.)

Mr. William Gossage, of Lancashire, patented (July, 1862) a method of obtaining soda or potash from the corresponding chloride, and by aid of silica or alumina, or both. Filling a suitable reservoir with fragments of one of these earths (and which he terms "decomposing substances"), he passes through the interstices of the mass the alkaline chloride in a state of vapor, along with steam-the whole being at a high temperature: in the fabrication of soda, the chloride of sodium being employed, silicate or aluminate of soda, or both, as the case may

be, result. The silicate is directly useful for glass-making, etc.; or either of the salts named may be treated with caustic lime, setting free caustic soda, which can then be carbonated.Newton's Lond. Jour., vol. xvii., 1863.

A process is stated to have been devised by Mr. Weldon (England), for the almost immediate production of bicarbonate of soda, by pumping into strong vessels containing equivalents of magnesia and common salt, the air passing through a coal fire, and charged of course with carbonic acid,-chloride of magnesium and bicarbonate of soda resulting.

Soda from Cryolite.-The interesting mineral, cryolite, found as yet in but few parts of the earth, and most largely perhaps in Greenland, is, as previously stated, a double fluoride of sodium and aluminium. It has been brought into use recently as a source from which to obtain both the earth-metal and the alkalimetal bases present in it, the employment of the mineral with such view having been, it is said, introduced by Prof. Julius Thomsen, of Copenhagen. Of the product of the Greenland mines, a considerable quantity had been already contracted for yearly in Denmark (and perhaps in Germany also), when about the close of the year 1864, the "Pennsylvania Salt Manufacturing Company," having its works near Pittsburg, through agents sent to Copenhagen for the purpose, contracted with Messrs. Shure and Sons, owners of the mines, and with the Government, for all the excess yearly of the cryolite mined, over the quantity previously secured for European consumption. Ships were thereupon chartered in England, at Quebec, and in American ports, to proceed to Ivigtus, Greenland, lat. 59°, load with the mineral, and deliver it at Philadelphia. The force at the mines has been increased, and the American contract is said to cover from one-half to twothirds of the total product. Up to October, 1865, about 6,000 tons of cryolite had been imported for the works of the company referred to, and the quantity received in 1866 was expected to be about 11,000 tons.

The process of extraction is said to be essentially the Danish: cryolite and lime are pulverized, mixed, and calcined: fluoride of calcium and aluminate of soda result; and the latter being treated with carbonic acid, carbonate of soda is formed, being of course soluble in water, while the alumina is precipitated. Besides the bicarbonate named, the company produce from the cryolite also caustic soda, salsoda, and the concentrated soda-lye, or "saponifier;" the last-named product being original with them, and patented.

Oxidation of Crude Soda Liquors.-The lye obtained from crude soda, or "black ash," usually containing a small quantity of sulphide of sodium, of which, especially for the preparation of the solid caustic soda, it is desirable to be rid, Mr. J. Hargreaves, of Lancashire, has invented an apparatus intended to be used (in place of the old methods with atmospheric air,

nitre, bleaching powder, etc.) for converting the sulphide into the insoluble and easily removable sulphate of soda. The principle is that of blowing through the lixivium, contained in a deep vessel, and from the bottom upward, a current of mingled steam, at 40 lbs. pressure, and air. Oxidation of the sulphide takes place; and in course of a few hours the conversion into sulphite, and from that to sulphate is so nearly complete, that the use of an extremely small quantity of nitrate in the solution then suffices. See Chemical News, June 8, 1866.

Sulphate of Soda and Chloride of Potassium from Sea-water.-M. Balard, after years of study and labor, has succeeded in extracting economically from sea-water the two substances named, and which are of so great importance in connection with a class of large chemical works. The usual production of the first, involving an immense consumption of common salt and sulphuric acid, has been described; while for the salts of potash the dependence has hitherto been largely upon the ashes of North American forests. M. Balard's plan has been thought likely to place the French nation independent alike of both these sources of supply. In this plan great quantities of sea-water are in the early spring run from the Mediterranean into large shallow reservoirs. During the summer, evaporation to some extent occurs, and a quantity of common salt separates; and the concentrated liquor is then stored in other reservoirs until winter. It is then again run back into the shallow pits, in which, during a cold night, it throws down large quantities of sulphate of soda. The mother-liquors remaining after this deposit are next introduced into a Carré's apparatus, and exposed to an intense cold; they thus yield considerable quantities of a double chloride of magnesium and potassium; and this, subjected to heat in a furnace, gives chlorhydric acid, magnesia, and chloride of potassium.

In M. Carré's method, cold is produced by means of a saturated solution of ammoniacal gas contained in one of two suitably-connected vessels: by heating this one, the gas is driven over into the other, and in which, surrounded by cold water, it liquefies by its own pressure. The heat being removed from under the first vessel, its temperature falls; the liquid in it reabsorbs the gas which had been driven off, and the rapid evaporation of the latter from the second vessel, into which it had been condensed, now necessitates a corresponding absorption of heat from contiguous solids or liquids: the liquors previously referred to being at this point brought in contact with the walls of the second vessel, the precipitation already mentioned takes place.

Preparation of Pure Soda.-M. Wöhler (Liebig's Annalen, September, 1861) finds that when nitrate of soda is heated along with binoxide of manganese in closed vessels, no manganate of soda is formed, and the decomposition is so complete that this process may be used for the preparation of a pure caustic soda.

SOLID BODIES, THE FLOW OF. M. Tresca has devoted much attention to this interesting subject, and recently laid the results of his investigations before the "Society of Civil Engineers in France." His experiments were conducted with the ordinary metals, lead, tin, copper, iron, and others, and the whole process may be described as liquefying the substances by pressure, and observing their behavior when issuing in jets from a small orifice. A strong cylinder having a small round hole at the bottom, was filled with the metal in its natural cold state (excepting iron and other peculiarly refractory metals), and a sufficiently powerful pressure applied at the upper extremitywhereupon the metal issued from the orifice in a jet like that of a liquid. Iron and other refractory metals it was necessary to heat to a certain point-not the melting point-before the same results could be obtained with facility. M. Tresca observes that the flow of solid bodies offers advantages for observing the vena contracta, and the laws regulating phenomena of this nature better than the flow of liquid bodies. The molecules under the pressure to which they are subjected assume, if not a true liquid form, at least a condition of extreme divisibility closely approaching thereto. In the cylinder alluded to, a mass of lead exactly fitting its internal diameter was forced in a jet through the orifice. No particulars with regard to the motion or arrangement of the molecules could be observed in this jet; but, on repeating the operation with the substitution of a number of thin disks of lead, in place of one solid mass, the following remarkable results were noted. By cutting the jet transversely, it was observed, after a little time, that a portion of all the disks issued simultaneously from the orifice in the shape of concentric tubes, or hollow pipes, one inside of the other; the lower disks formed the external tubes, and the upper disks the internal tubes; the behavior of the flow being precisely similar to that of water, passing through the orifice of a cylinder, the upper strata of the fluid supplying the internal particles of the jet, and the lower strata the external ones. With twenty disks of lead, having a diameter of 3.9 inches, and an aggregate thickness of 2.35 inches, a jet was obtained 23.4 inches long, the diameter of the orifice being from .786 to 1.96 inches. The contents of the unbroken jet issuing from an orifice of 0.786 inches in diameter were rather more than one-third the whole mass of the metal in the cylinder. With a larger hole, the whole contents would have been voided in a single jet. With smaller orifices the jets were proportionately longer, but retained the same characteristics. Other metals acted upon furnished similar results, and by exercising great precautions, the external and internal tubes could be separated from each other. Small waxen tablets under the same conditions behaved in exactly a similar manner.

A mass of metal in a mould may be imagined

to consist of two concentric cylinders, one corresponding to the orifice of the flow, and the other enclosing it. When pressure is given to the upper surface, the whole exterior cylinder becomes compressed, and gives rise to the flow by driving out the central portion by a uniform pressure all around it. In fact, the flow takes place more strictly in accordance with the law of concentricity of layers than that of parallelism of sections.

The crushing of solid bodies is attended with phenomena analogous to those above described. When a block of tin composed of several disks is subjected to a crushing force, a progression of particles from the centre to the circumference occurs, and the disks take the shape of lenses grouped uniformly around the axis of a cylinder. Other metals, such as lead, and the substance wax, behave similarly. Again, it is known that in crushing a mass of metal consisting of concentric cylinders a bulging takes place at about the middle of the height. The sides of the exterior cylinders deflect, but still preserve their continuity. If we suppose a cylinder of lead to be made up of concentric tubes, the lengthening of either the external or internal tubes can be produced at pleasure, accordingly as heavy or light blows are struck upon it. The shock of a heavy blow will be transmitted to the central tubes, while that of a light blow will be wholly expended on the exterior tubes. A knowledge of these facts is of practical value in the stamping of metals.

SORGHUM. The sorts of cane indigenous to China, as perhaps also to parts of the East Indies, and to Southern Africa, which thrive and perfect their juices and seed in higher latitudes than does that long and specially known as the sugar-cane," belong to the family of grasses, and more specifically to the millets. Not only the Chinese cane (sorghum saccharatum; Fr., sorgho sucré; Ital., sorgo), and the African cane, or imphee, but also the dourah corn and the broom-corn, are now accepted as but varieties of a single primitive species, sometimes referred to Holcus, and sometimes to Andropogon (being, in this view, the A. sorghum); or, indeed, by some writers, as constituting a distinct genus, on which hypothesis the sugar-bearing millets form the species, sorghum vulgare. Thus, the generic term "sorghum " embracing all the varieties, these may then, in common language, be properly distinguished according to their source under the names of "sorgho" and "imphee." The history of the introduction of these plants into Europe and this country is already generally known.

Mr. William Clough, of Cincinnati, states that the several sub-varieties of imphee, originally described by Mr. Wray under the native titles, have, in this country, already become so far modified and assimilated in their characters that but five or six distinct sorts can now be traced; while, except in the case of the Boomsee-a-na and the Nee-a-za-na, there is scarcely