Boullay, and gallic acid by Berzelius; the proportions they obtain are as follow: equal to three proportions oxygen, three hydrogen, and six of carbon. Hence it was supposed, that gallic acid differed only in water of crystallization, but all attempts to deprive it of water, and convert it into ulmic acid, failed. The ulmates of the metals, although insoluble in saline solutions and in excess of ammonia, are, when well washed, soluble in water, like the ferro-prussiate of iron. They take fire at a temperature much below a red heat, and burn. Three of them were found by experiment to be composed, per cent., as follows: Hence the equivalent of the acid consists of fifteen proportions of oxygen, fifteen of hydrogen, and thirty of carbon, which, taking hydrogen as unity, is 315. This is precisely five times the number of gallic acid. The feeble capacity of saturation possessed by ulmin may, perhaps, be important in nature, for a large quantity of this food of plants may in consequence be transmitted to them from decomposing substances, by small quantities of alkali or ammonia. The earthy ulmates, and especially that of lime, are not quite insoluble, and withal are capable of being suspended so perfectly in fluids as to be useful in the nutrition of plants, whilst still they are not so likely to be washed away as the soluble ulmates. Azulmic Acid.-By this name M. Boullay designates a substance which has the same kind of relation to ulmic acid that azoted organic matter has to such as is of vegetable origin. The carbonaceous product left by the spontaneous decomposition of hydrocyanic acid is azulmic acid, and not a carburet of azote. It contains hydrogen, and can combine with salifiable bases in the same manner as hydrocyanic acid itself. Azulmic acid is not soluble either in hot or cold water or alcohol: strong cold nitric acid dissolves it, forming a reddish solution, precipitable by water. The alkalies dissolve it very freely, producing deep-coloured solutions: the acids precipitate these solutions, as do also the metallic salts. By heat azulmic acid gives first hydrocyanate of ammonia, then cyanogen, and leaves carbon. When analysed, the proportion of azote to carbon was in volumes as 2 to 5. Hence, upon theory, it will consist by weight per cent. of 47.64 azote, 50.67 carbon, and 1.69 hydrogen. Pursuing the analogy between ulmic and azulmic acid, M. Boullay endeavoured to form the latter by heating gelatine with potassa, in imitation of M. Braconnot's process for forming ulmin; and, in fact, azulmic acid appeared to be produced. Azulmic acid is pro duced also not only by the spontaneous decomposition of hydrocyanic acid, but by those of hydrocyanate of ammonia, of cyanogen dissolved in water, by the action of cyanogen upon bases, and indeed whenever compounds of this substance are experimented with. The action of weak nitric acid on cast iron, or the carbon it contains, produces a similar substance; and as azulmic acid appears to combine with concentrated nitric acid, there is reason to believe that artificial tannins are only combinations of this body with nitric acid, or at least that they contain an analogous substance*. 15. ON CASEUM AND MILK.-(Braconnot.) An excellent, because practical memoir on milk has been published by M. Braconnot, in the Annales de Chimie, xliii. 337, which offers many applications of a substance long but not thoroughly known, not a few of which we anticipate will hereafter come into use. This substance is caseous matter, or, as he has called it, caseum. Soluble Caseum, and its Applications.-2500 parts (grammes) of the curd of new cheese, as sold in the market, were heated to 212° for some time: it contracted, and became a glutinous elastic mass, swimming in much serum. Being washed in boiling water, to remove the acid serum, and dried, it weighed 469 parts. It was a compound of caseum with acetic and lactic acids: being divided, put into sufficient water with 12.5 parts of crystallized bicarbonate of potassa, and heated, it dissolved with effervescence, producing a mucilaginous liquor, distinctly reddening litmus paper. Being evaporated carefully, with continual agitation, it left a soft portion, which, as it cooled, acquired consistency, was drawn out between the fingers into thin portions, and then dried in the air upon a sieve: it weighed 300 parts. This soluble caseum is a surcaseate of potassa, containing still butter and salts. It resembles isinglass, is of a yellow-white colour, translucent, and of a stale taste: it is perfectly soluble in hot or cold water, producing a fluid rendered milky by the presence of butter. In this impure state the substance is easily prepared instead of the bicarbonate, the potash or soda of commerce may be used. The following are hints for its application. Like gelatine, it may be preserved without alteration for any length of time, and may be obtained in enormous quantities, if required. Associated in various ways with food, it must prove of the greatest importance on board vessels for long voyages. Its aqueous solution, sugared and flavoured with a little lemon-peel, makes an agreeable and nourishing drink for invalids. It is a powerful cement: its solution, evaporated on glass or porcelain to dryness, cannot be removed without injury to the vessels; its hot concentrated solution has been applied with great success to join glass, porcelain, wood, and stone. The same solution forms a brilliant varnish: being applied to paper, it Annales de Chimie, xliii. 273. makes labels, which, when moistened and attached, adhere with great force. It may be used instead of isinglass in dressing silks, ribands, gauze, preparing artificial flowers, &c. It has not answered in endeavours to clarify beer, but is equal to milk or cream in the clarification of table liqueurs, giving them the softness and qualities of age. It may be used in place of creamed milk in the clarification of beet-root, sugar, syrups, &c., in conjunction with animal charcoal, without exciting any fear regarding the presence of serum. M. Braconnot thinks also, that by the help of a little ammonia the greater part of the curd previously separated as above from its serum may be taken up and converted into a dry substance, which, with the help of earthy salts, will be of great service in clarification: for, having dissolved some of this preparation in water, a small quantity of muriate of lime, sulphate of magnesia, or even sulphate of lime in powder was added: the liquid remained clear whilst cold, but the slightest effect of heat made it coagulate uniformly throughout; the coagulum gradually contracted, and a perfectly clear liquid issued from it. Milk has always been considered as a certain antidote in some cases of poisoning. The soluble caseum will perform the same office against most of the metallic salts, but there is reason to believe that white of egg is better than either against corrosive sublimate. Chemical Properties of Caseum.-Caseum is an acid which, because of its tendency to combine with almost every substance, it is very difficult to obtain pure. The soluble caseum already described is to be dissolved in boiling water, put into a funnel, the aperture of which is stopped, and left until a layer of cream has collected on the surface. After removing this, a little sulphuric acid is to be added, which will form a clot of sulphate of caseum: this is to be well washed and then heated in water, with just enough carbonate of potash to dissolve it. The mucilaginous liquor formed is, whilst hot, to be mixed with its volume of alcohol. It is necessary that no deposit form at the moment; it should occur only in the course of twenty-four hours, and will include the butter, the sulphate of potash, and part of the caseum. All is to be placed on a cloth, and a clear transparent liquid will pass, which, evaporated to dryness, leaves caseum pure, except in retaining a minute portion of potash. Caseum, or caseic acid, thus obtained, is a dry diaphanous substance, resembling gum arabic in appearance, and unalterable in the air. It reddens litmus paper, is soluble in hot or cold water, forming transparent viscid adhesive solutions, yielding by evaporation transparent pellicles, which again dissolve in water. The mineral acids, except the phosphoric, when added to the liquor, unite to the caseum, and produce white, opaque, coagulated, insoluble masses. Very weak solutions are not thus coagulated, as may be seen by adding a little diluted sulphuric acid to such; heat does not cause the effect, but the moment a little lime is added it happens at once. Milk with twice its bulk of water is not coagulated by sulphuric acid cold, but apply heat and the effect is produced, because a little phosphate of lime in the milk then becomes sulphate, and acts as above. Generally, the combinations of cheesy matter with acids are imputrescent. Well washed sulphate of caseum was left with water for a long time: it gradually disappeared, but produced no putrid odour. Vegetable acids precipitate caseum, unless in excess. Potash, soda, and ammonia produce very soluble compounds with it, which are perfectly transparent, unalterable by air, and resemble gum. All earthy bases and metallic oxides form insoluble compounds. All salts, except those with base of potash, soda, or ammonia, combine with caseum to form insoluble compounds. Even a little selenitic water put into a solution of caseum, though it causes no change at first, yet, when heat is applied, produces insoluble pellicles, which are a compound of the caseum and earthy salt. The same or still more striking coagulation happens with sulphate of magnesia and acetate of lime. Strong alcohol does not affect caseum; weak alcohol dissolves it. Sugar renders a solution of caseum more liquid: gum arabic renders it quite insoluble, probably from the presence of earthy salts in it. Infusion of galls acts with it as with gelatine. M. Braconnot suspects that vegetable albumen is nothing more than caseum with some earthy salts present. Improved Milk.-Besides caseum and butter, milk contains salts, &c. which are not particularly desirable. M. Braconnot took 2 litres (4.4 pints) of milk, heated it to 113° F., gradually added dilute muriatic acid, and agitated the whole. The curd formed contained the caseum and butter, and, being separated from the whey, was gradually mixed with 5 grammes (77 grains) of crystallized sub-carbonate of soda, reduced to powder and warmed. No water was added, but the whole gradually dissolved. It had the weak acidity of recent milk, and formed about a half-litre of cream (a fifth of the first bulk), capable of numerous applications in domestic economy. If made up to its first bulk with water and a little sugar, it forms a milk more agreeable than the original; or it may be flavoured, &c., and used as cream. If it be heated with about its weight of sugar, it becomes remarkably fluid, and forms a perfectly homogeneous syrup of milk, which will keep for any length of time, and which, by the mere addition of a sufficient quantity of water, forms a perfectly homogeneous white opaque liquid, which is in every respect like sugared milk of improved flavour. The syrup diluted with water forms a nourishing drink for invalids. Carefully evaporated, but not beyond a certain limit, or the butter would separate, it gave, when cold, a soft confection, which left for a twelvemonth in a loosely stopped bottle, underwent no change. This, when exposed in thin portions to the air, was rendered quite dry, and could then be crushed and kept for any length of time without change, being always recon. vertible into useful states by the mere addition of water*. 16. MANUFACTURE OF CHARCOAL. A new process, recommended in the Journal des Forêts, for this purpose, is to fill all the interstices in the heap of wood to be charred with powdered charcoal. The product obtained is equal, in every respect, to cylinder charcoal; and, independent of its quality, the quantity obtained is very much greater than that obtained by the ordinary method. The charcoal used to fill the interstices is that left on the earth after a previous burning. The effect is produced by preventing much of the access of air which occurs in the ordinary method. The volume of charcoal is increased a tenth, and its weight a fiftht. Mr. Doolittle, of Birmington, United States, has lately charred wood in kilns constructed for the purpose. One was built of brickwork, thirty feet diameter and nine feet high, to the opening of the arch which inclosed the top. It had openings at the top and sides for the purpose of admitting air, charging, extracting, &c., all which openings were under regulation. The charcoal thus obtained was exceedingly good in quality, free from stones, earth, &c., and very abundant in quantity, the increase being, in the latter respect, sometimes half as much more as the old mode of burning would give‡. 17. POTASH OBTAINED COMMERCIALLY FROM FELSPAR. According to M. Fuchs, this important alkali may be extracted from minerals containing it, by the following method:-They are to be calcined with lime, then left for some time in contact with water, and the liquor filtered and evaporated. M. Fuchs says he has thus obtained from nineteen to twenty parts of potash from felspar, and from fifteen to sixteen from mica, per cent§. 18. SALE OF SELENIUM. Perfectly pure selenium (free from sulphur) is announced for sale, at the price of four gold Frederics (ninety francs) per ounce of Cologne (446 grains). Applications, post paid, with the money, is to be made to the Ducal Office of the Mines of Harzgerode, in the duchy of Anhalt. * Ann. de Chim. xliii. 337. Bull. Univ., D. xiv. 262. § Ann, de l'Industrie, v. 278. |