in winter and in summer, the vapours are less dense, but the quantity of boracic acid deposited is greater. Increased vapours indicate unfavourable change of weather; and the lagoons act as infallible barometers to the neighbourhood, even at a great distance, serving to regulate the proceedings of the peasantry in their agricultural pursuits. (Dr. Bowring.)

The different manufactories contain from one to five batteries, each comprising fourteen or sixteen evaporating pans. The number of lagoons to each establishment varies from three to twenty-five. The largest lagoons are from fifteen to twenty metres (from forty-nine feet to sixty-six feet nearly) in diameter, and the smallest from four to five metres (thirteen feet to sixteen feet and a half); their depth varies from one and a half to two and a half metres (five feet to eight feet three inches).*

Before describing the process of converting the crude boracic acid into borax, it will be proper to

"It appears to me," observes Dr. Bowring, " that the powers and riches of these extraordinary districts remain yet to be fully developed. They exhibit an immense number of mighty steam-engines furnished by nature at no cost, and applicable to the production of an infinite variety of objects. In the progress of time this vast machinery of heat and force will probably become the moving central point of extensive manufacturing establishments. The steam, which has been so ingeniously applied to the concentration and evaporation of the boracie acid, will probably hereafter, instead of wasting itself in the air, be employed to move large engines, which will be directed to the infinite variety of production which engages the attention of labouring and intelligent artisans ; and thus, in the course of time, there can be little doubt, that these lagoons, which were fled from as objects of danger and terror by uninstructed man, will gather around them a large intelligent population, and become sources of prosperity to innumerable individuals throughout endless ages."

advert to M. Payen's researches on the nature of the substances which accompany the boracic acid, and his theoretical views of the origin of the products.

The vapours are not entirely condensable; a gas is given off, which on examination proved to be a mixture of carbonic acid, nitrogen, oxygen, and sulphuretted hydrogen in the following proportions:

The condensable products and the substances brought up mechanically by the powerful current of vapour, are the following:-water, clay, sulphates of lime, ammonia, alumina, and iron; hydrochloric acid; organic substances possessing a marine smell (probably like that of sea-weed), sulphur, and the merest trace of boracic acid. The temperature of the vapours was found to vary between 206° and 212° Fahr. (97° and 100° Cent.). No boracic acid could be obtained by condensing the vapours of the soffioni in large and long tubes; the product was only an acidulated water containing no boracic acid. To obtain the latter, it seems essential that the vapour should be brought into contact with water; and it is often observed that a portion of the water absorbed, when a lagoon is filled, is subsequently ejected by the vapour. Thus the production of boracic acid, or rather the arrival of the acid to the surface of the earth, seems to depend on the introduction of water through the fissures.

From these observations M. Payen draws the fol

lowing theoretical conclusions: All the phenomena would be perfectly intelligible, if it be admitted that the water of the sea, penetrating through some fissure to a great depth, may have its temperature raised to a high degree, and find in the soffioni an exit for its vapours. The boracic acid would then be derived from deposits of that substance, through which the vapours and the projected water rush ; and the sulphuretted hydrogen from the decomposition, by means of boracic acid, of sulphurets formed by the reaction of the organic matter contained in the water on the sulphates also present in the water.

66

These facts admit, however, of a more chemical explanation. Admitting with M. Dumas," observes M. Payen, "that a deposit of sulphuret of boron, situated at a great depth, came into contact with seawater, a lively action would take place, from which would result boracic acid, sulphuretted hydrogen, a high temperature which would carry off these products with the water, hydrochloric acid arising from the decomposition of earthy chlorides, and ammonia produced by the organic matters. If the action take place at a little distance from a calcareous mass, the boracic acid conveyed in the current of vapour would decompose the carbonate of lime, and the equivalent of carbonic acid would mix with the other gases; at a certain distance the sublimed boracic acid might form deposits, and according as the water of the lagoons descended to this point, or not, the return current would carry up with it boracic acid, or pass without volatilizing the acid.

"The air furnished by the sea-water, or other source, would enter the fissures, and determine, in

the presence of sulphuretted hydrogen, the formation of sulphuric acid. This, in its turn, would produce sulphates of lime, of ammonia, of alumina, and of iron, taking the lime from the calcareous mass, the ammonia from the vapours, the alumina and iron from the clay. These different salts, which are formed or which dissolve in the waters near the surface of the soil, explain the disintegration of the latter. The appearance of sulphur, and the presence of a little oxygen, which accompany the various substances contained in the soffioni and in the troubled waters of the lagoons, would proceed from the accidental introduction of air."*

III. MANUFACTURE OF BORAX FROM BORACIC ACID.

As sent out of the establishments, the boracic acid is commonly far from being a pure substance, and the proportion of impurities, moreover, is said to be continually on the increase. Formerly the product contained from 90 to 92 per cent. of pure crystallized boracic acid; at present, the proportion varies

* M. Payen suggests that a portion of the boracic acid may be produced by the re-action of sulphuric acid, so abundant in masses of disintegrated soil, on anteriorly formed borate of lime.

Neither of the above hypotheses presents a satisfactory explanation of the origin of the ammonia which always accompanies the native boracic acid in considerable quantity; the organic matters which would be introduced by the sea-water being far too small in quantity to be admitted as the probable source of the ammonia. It is suggested by Mr. Balmain that this body may be produced by the decomposition, by means of water, of athogen, or some analogous compound of boron and nitrogen, which, when heated with water, becomes decomposed, with formation of boracic and free ammonia; the oxygen of the water having united with the boron, and the hydrogen of the water with nitrogen.

between 74 and 83 per cent. This is attributed to the progressive alteration of the disintegrated strata by the currents of vapours and the infiltrations of

water.

The crude acid has been subjected to a complete analysis by M. Wittstein, in which he obtained the the following results (Buchner's Repertorium, xxii. 145):

Crystallized boracic acid, (BO, + 3 HO)
Sulphate of manganese

76.494

a trace

It has been a matter of surprise that no steps are taken to purify the acid on the spot, as a very considerable expenditure in packages, freight, &c., might thereby be avoided. The impurities may be removed to a great extent by subjecting the drained acid to a strong pressure, and purifying the residue by washing; and one half of the water contained in the crystallized acid might be expelled by a prolonged desiccation at 212°, whereby the proportion of dry or real acid in the impure material would be increased from 56 to 72 per cent.

But some borax manufacturers consider a given