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

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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

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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

animals in reference to the foregoing experiments, and concludes, in opposition to that theory, that the butter in the milk could not have arisen solely from the fat contained in the food. Hence it must be produced by a separation of oxygen from the elements of the unazotized ingredients of the food of the animal, in the manner pointed out by Liebig. He then quotes, in favour of the same conclusion, several experiments of Boussingault, and observations of dairymen in different localities. Potatoes are particularly favourable both to the flow of milk and increase of butter, from the starch they contain; so is malt-refuse. Porter and beer are also well known to be favourable to the production of butter both in the milk of woman and of the cow, although these fluids do not contain fat.

The production of caseine in the milk is then considered in reference to the quantity of albumen in the food supplied on different days to the cow, and to the supposed destruction of the tissues by muscular exercise. Pasturing in the open field is more favourable to the formation of caseine, while stall-feeding is more favourable to the formation of butter.

It is then shown that the proportion of butter in the milk of woman is increased by rest and the diminution of the respiratory oxidation; and the paper concludes with some practical remarks on the mode of preserving milk.

Meeting of the Royal Institution.

Friday, Jan. 27, 1843.

The lecture for this evening was by Professor Brande, and the subject, starch. After tracing the origin of the varied kinds of this substance which are commonly met with in everyday life, as the varieties of starch, sago, tapioca, arrow root, tous les mois, &c., and describing the sources from which they are derived, the Professor exhibited the properties of gluten and its solubility in acid or alkaline menstrua, and entered very fully into the manufacture of the ordinary starch from wheat, and that lately introduced made from rice; the first through the medium of acids, produced by the slow fermentation of the wheat, and in which the gluten is soluble while the true fecula subsides; and the latter by the employment of caustic soda as a solvent for this azotized body. The various stages of these processes were fully treated of, and the peculiar characters of the resulting substances exhibited. The properties of starch, its tests by solutions of iodine in an uncombined state, and the means of rendering it free when in combination by chlorine and galvanic agency, were beautifully shown by two well-conceived illustrations; one of them consisted in a small flask filled with chlorine gas, attached to a long cylindrical exhausted receiver, in which had been placed a card with the word starch written on it in large characters, with a mixture of an iodide and solution of starch. On opening the communicating stopcocks so as to admit the chlorine, the iodine was gradually liberated, and, acting on the starch, the letters became of a deep blue colour.

The employment of starch in stiffening and dressing various fa

brics, as calico, linen, &c., in the manufacture of British gum and dextrine, the peculiar actions of sulphuric acid and diastase in the formation of sugar, and the saccharine worts of the brewer and distiller were then detailed; the supposed important part that this substance plays in the animal economy, in the formation of fat, briefly noticed; as also the conversion of this body into sugar during germination, thus supplying valuable food to the young plant as it was required.

The whole of this interesting demonstration, replete with useful and valuable information, was illustrated by a series of accurate botanical and microscopic sketches of the various kinds of starch and some of the plants from which they are derived, for which, and also many interesting preparations, the Professor stated that he was indebted to the kindness of Dr. Pereira.

The microscopic configurations of the various kinds of this substance, with their beautiful appearance when viewed by polarized light, were exhibited in the library by Mr. Ross at the close of the lecture.

Friday, Feb. 3, 1843.

Mr. E. Solly, Jun., on "Smoke and its Consumption."-This subject, so important to every manufacturer and inhabitant of this smoky metropolis, and indeed we may say of the United Kingdom in general, was treated in a very clear and instructive manner on the above evening. Mr. Solly apologized for beginning his lecture on the most elementary principles of combustion, but from many in the assembly being unacquainted with the scientific groundwork of the subject, this was imperative.

The elementary constituents of the combustible bodies in general use were fully detailed, and the principles on which these elements burnt or were oxidized explained and well illustrated: the necessary adjuncts to their perfect oxidation, so as to prevent any deposition of their carbon in the form of soot or smoke, shown by various experiments; and ultimately the numerous methods that have been invented or proposed by different individuals within the last twenty years, discussed and exhibited by a series of coloured sectional sketches, arranged so as to divide the inventions into the distinct principles on which they were founded, as, for instance,-1st, those where the combustion was effected by a downward current of the smoke, through the red and glowing body of fuel; 2nd, in which a current of air was made, to enter over the surface of the burning fuel; 3rd, where a current of air was made to meet the smoky products of the combustion at the extremity of the fuel or bridge; 4th, the cases in which air previously heated was admitted in the same way and for the same purpose, avoiding the cooling attendant on the previous method; 5th, where the unconsumed carbon, &c. was made to traverse a considerable length or a second chamber of clear burning fuel; and 6thly, in which the whole of the bars of the furnace which support the fuel were made to move gradually from the point at which the fresh fuel was being delivered. The lecture was illustrated by some good experiments, some of which we cannot

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