is incessantly manifested, and an evaporation exceeding 80,000,000 of kilogrammes effected, in which an annual production of 750,000 kilogrammes of crystallized acid is realised, neither machines, nor crude substances, nor combustibles, are perceptible! The soffioni furnish everything; it is merely requisite to give their powerful blast a proper direction to obtain both the crude solution and the heat required.

Many difficulties have impeded this manufacture; but M. Larderelle has succeeded in overcoming the most serious by substituting, instead of the expensive wood fuel, a most happy application of the superabundant vapour which everywhere escapes from the soil.

Before describing the actual processes of manufacture, and proposing a probable theory and possible improvements, I will give the results of my researches as to the nature of the gases, and of the substances which they carry with them into the lagoons.

The non-condensed gases were found to consist in 100 parts of— Carbonic acid...

57.30

34.81

6.57

1.31

100.00

The condensible products and the substances conveyed by the currents of vapour vary: generally they comprise water, clay, sulphate of lime, of ammonia, of alumina and of iron, hydrochloric acid, organic substances with a marine smell, and, lastly, little or no boracic acid; they deposit sulphur in all the narrow fissures and porous bodies which they traverse. The temperature of these vapours was found to vary from between 206° Fahr. to 212°. With these observations we shall be able, in connexion with what follows, to offer a probable theory of the production of boracic acid.

It has been found impossible to obtain this acid by condensing the vapours of the soffioni even in very large and long tubes; to obtain it, it is requisite that their apertures should be directly covered by the liquid of the basins; it is frequently observed that a portion of the water absorbed when these lagoons are filled, is subsequently thrown up by the vapour.

Thus the cause of the currents of gas, and of the elevation of the temperature, appears to have remained constant for many years, whilst the production, or at least the arrival of the boracic acid at the surface of the soil, seems to depend on the introduction of water into the fissures.

Suppose the water of the sea percolating through some fissure to a great depth had its temperature raised to a high degree, and that it found in the soffioni an issue for its vapours, all these phænomena would be intelligible; for the vapour mixed with the projected water, in passing over the deposits of boracic acid, would carry this with it, and by the reaction of the organic matter contained in it on the sulphates would produce sulphurets, from which boracic acid would expel sulphuretted hydrogen.

These facts admit however of a more chemical explanation. Let us suppose, with M. Dumas, that a deposit of sulphuret of boron, situated at a great depth, came in contact with sea water, a considerable 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 took place not far from the 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 current would again carry up with it boracic acid, or pass without volatilizing it.

The air furnished by the sea water would enter the fissures, and in the presence of sulphuretted hydrogen would determine 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 litttle oxygen, which accompany the various substances contained in the soffioni and in the troubled waters of the lagoons, would result from the accidental introduction of air*.

The methods adopted in the nine manufactories are, with some slight modifications, identical; they consist in the construction of rude circular basins around each of the centres of eruption, where two or several of the more considerable fissures terminate; and further, in conveying into the highest of these basins or lagoons, A, the water of some neighbouring springs. After remaining there for 24 hours, during which these waters have been constantly agitated by the subterraneous vapours, the plug o is opened, and the liquid passes by a small canal, mn, into the lower lagoon B, where it is confined for the same time, and becomes charged with more boracic acid, and the accompanying substances. The solution is successively passed into the lagoons C, D, and the liquid drawn off from an inferior basin constantly replaced by that contained in the one abovet.

When a solution has arrived at the last lagoon D, and is sufficiently saturated, it is transferred into a reservoir or cistern E, six metres square and one deep, where the greater portion of the sediment is deposited.

* Another cause may have a great influence in the production of boracic acid, for instance the reaction of sulphuric acid, so abundant in the masses of disintegrated soil on the anteriorly formed borate of lime. It is possible that one day some of these deposits of borate of lime may be discovered by means of excava tions and analysis.

† All experiments made with a view of obtaining direct the boracic acid by condensing the vapours in conduits have been in vain; only an acidulated water, containing no boracic acid, was obtained.

The supernatant liquid is decanted either into a second reservoir F, or direct into two batteries, each of 7 leaden evaporating pans, GG,

2.90 in breadth and 0-35 in depth, supported by strong wooden rafters above the masonry on an inclined plane, which allows the vapour of some soffioni inclosed in drains, and which enter at H, to ascend freely beneath the pans, which are arranged on different levels, to the upper portion, where the excess is given off outside the manufactory. The solution of the boracic acid in the reservoirs usually has a specific gravity of 1° to 15°.

The four first pans of each double range are filled with the clear liquid by removing the upper plug p. At the end of 24 hours, the solution, diminished to about one-half of its volume, is transferred by means of siphons into the next pans of each range, which is replaced by the product of a fresh decantation from the reservoir. 24 hours later, the solution, again reduced to half of its volume, is removed by means of siphons into the two last pans, while the two superior ones are again charged as before. The evaporation in the two last pans is continued for 24 hours, and the mother-waters of a preceding crystallization mixed with it; the mixture then indicates from 10° to 11° at a temperature of from 173° to 176°

Fahr. The whole of this solution is then brought into the crystallizing tubs, which are constructed of wood and lined with lead, Here the crystallization is effected, and the produce of 72 hours' evaporation derived each day from a battery of 14 pans affords 90 kilogrammes of saleable boracic acid. This product diminishes in rainy weather. During evaporation abundant deposits of sulphates of lime are formed, which have to be removed.

When crystallization is at an end the mother-ley is drawn off and added to the last evaporating pans; the acid is placed in baskets, C, to drain; it is then carried into the drying-room and spread into layers on the floor, and turned from time to time; when it no longer moistens the hand on being pressed, it is formed into heaps, packed in casks and forwarded to Leghorn. The drying-room is con

structed of bricks, and has a double floor, between which the vapour of some soffioni circulates.

The different manufactories contain from 1 to 5 batteries of from 14 to 16 pans, and each from 3 to 25 lagoons. In the manufactory of Larderello, which is the most considerable, there are 80 evaporating pans.

The largest lagoons, which are of an irregular circular form, are from 15 to 20 metres in diameter, and the smallest from 4 to 5 metres; their depth varies between 1.5 to 2.5. The liquid attains in them a temperature of from 200° to 203° Fahr.

Unfortunately the impurity of the acid increases each year, which is probably due to the progressive alteration of the disintegrated strata by the currents of vapours and the infiltrations of water. The first products contained from 90 to 92 per cent. of pure crystallized acid, at present they contain from 18 to 25 per cent. of foreign matters*.

These impurities render it unfit for several applications, and occasion a useless expense in transport. They might be got rid of by subjecting the drained acid to strong pressure, purifying the product by washing and treating the mother-leys apart, which would

* An analysis of the crude.acid by M. Wittstein was inserted at p. 90 of this Journal.-ED.

afford alum that might be turned to account, and residues of sulphate of lime, clay, &c.

Has, however, the maximum of production been attained?

This is not probable; to be convinced of this, and to find out the conditions favourable to a larger produce, it would be necessary to examine whether there exist accessible deposits of borate of lime, and to submit to numerous analyses the waters of the lagoons after they have been in contact with the vapours a certain time. In this manner the proportions of acid corresponding to the modified circumstances would be found. Perhaps frequent additions of cold water into the soffioni, after having been left dry for some time, would be favourable to a more abundant extraction of the acid contained in the subterraneous deposits.

[A very excellent abstract of the process of manufacture as described in the above paper, has been given by Dr. Pereira in his valuable work on Materia Medica, and an exceedingly interesting article on the same subject by Dr. J. Bowring, appeared in the Philosophical Magazine for July 1839. No notice, however, having appeared in English of M. Payen's views on the origin of the acid, we have been induced, from the interesting nature of the question, to place the entire memoir before our readers.-W. F.]

PROCEEDINGS OF SOCIETIES.

Chemical Society of London.

Jan. 17, 1843.-Prof. Thomas Graham, President, in the Chair. A paper was read, entitled, "On the Changes in Composition of the Milk of a Cow, according to its Exercise and Food." By Lyon Playfair, Ph. D.

The author of this paper states its principal object to be, to draw the attention of practical men to the conditions which effect a change in their dairy produce. After pointing out a defect in the mode of analysing milk practised by MM. Boussingault and Lebel, Dr. Playfair describes a modification of that method, which he practised and recommends as more exact. The cow being in good milking condition and at the time fed upon after-grass, he ascertained the average amount of her milk for five days, and then proceeded to analyse it. In the first day it was observed that the milk of the evening contained 3.7 per cent. of butter, and of the following morning 5'6 per cent. The deficiency in the first observation is referred to the consumption of a greater portion of the butter or its constituents, from respiratory oxidation during the day when the animal was in the field, than during the night when it was at rest in the stall. When confined during the day and fed with after-grass in a shed, the butter amounted to 5.1 per cent. When fed with hay, the butter was 3.9 and 4.6 per cent. When fed with portions of potatoes, hay and bean flour, the butter was 6.7 and 4.9 per cent. With hay and potatoes 46 and 4.9 per cent.

The author then examines Dumas' theory of the origin of fat in