LACTIC ACID is left in either the anhydrous or hydrated state in the retort, after the foregoing distillation of citraconic acid. 19.5 grammes of anhydrous lactic acid, exposed for eight hours to 500° F., gave the author 12.2 per cent. of aldehyde, 14.9 per cent. of lactide, and 1 per cent. of carbon. By raising the temperature to 572° F. and higher, the quantity of lactide and lactic acid were diminished, and the aldehyde increased. As the disengagement of the gas is much more violent, the gases must be more carefully cooled, to prove directly the increase of the aldehyde. The lactide produced is, for the most part, decomposed into aldehyde and carbonic oxide at this heat, which is much higher than the point of sublimation. The decomposition, therefore, of the lactic acid is simply as follows:-Lactide is first produced, and is decomposed at a higher temperature into 2 equivalents carbonic oxide and 1 equivalent aldehyde C4 H4 O2+2CO =C HO1. The presence of carbonic acid and the composition of citraconic acid seem to show that in the distillation a substance containing more hydrogen is formed, but it could not be isolated. LACTATE OF COPPER, submitted to distructive distillation, presents two stages of decomposition. In the first, at between 392° and 410° F., carbonic acid and aldehyde, and a little hydrated lactic acid are formed, the latter very likely owing to the crystals having retained some water of crystallisation. The retort contains metallic copper, and anhydrous lactic acid, which decomposes in the second stage at between 480° and 500° F. Lactates of powerful bases are decomposed differently. Dr. Engelhardt recommends the dry distillation of lactates of feeble bases for the preparation of aldehyde. ON AMDULIN: A MODIFICATION OF STARCH.* SCHULZE found that when starch is acted on in the same manner as for the production of dextrine, but the boiling interrupted by the addition of sulphuric acid when the starch is dissolved, and the hot liquid immediately neutralised with carbonate of lime, in a few days floculi deposit from the perfectly clear liquid, and may easily be separated by filtration. When dry they have the appearance of white sago, and the composition of starch. Schulze calls it amdulin. It has the same action as starch on iodine, but differs from starch in being completely soluble in hot water. *Pharmaceut. Central Blatt. ON THE COMPOSITION OF STEARINE.* BY G. ARZBAECHER. THE author was led by the irreconcileable statements concerning the composition o stearine in Gmelin's Handbuch der Chemie, to perform several combustions of stearine prepared from mutton and beef suet. The stearine was prepared by melting each part in a water bath, and agitating with ether. The beef melted at 117° and the mutton at 122° F. The ether, after cook ing, was poured off, and the stearine was pressed. This treatment was repeated four or five times. Thus prepared, the melting point of each stearine was found to be uniformly 141 F. Beef stearine yielded as a mean of four analyses, which agree well with those of Gay Lussac, and Lecan as will be seen from the following table : Arzbaecher. Chevrel. Lecanu. Carbon .. 78.74 78.78 100.00 78.74 12.27 8.99 0=100 or H=1 9.3 9.2 10.5 1 10.7 4 24.7 Carbon .... 54.9 54.8 55.7 12 55'4 .... M. Choubine adopted the No. 451.88 36.15 should have the formula Rammelsberg Mosander.. ..... C12 H12 NO4 + NO, HO. 580 600 554-88 44.39 46.40 48.00 Messrs. Laurent and Gerbardt make itC12 H13 NO4 + NO3, HO. Hermann Hermann denied the existence of didymium, and did not free the lanthanium from it. Consequently his atomic weight must be too high. M. Rost Van Tomniger proved similar results. Vlaanderen has also confirmed this formula, which must be adopted as the correct one. REDUCTION OF CHLORIDE OF SILVER.* BY M. WETTSTEIN. THIS chemist having made some experiments to determine the comparative value of the methods of reducing chloride of silver hitherto employed; namely, with carbonate of potassa, caustic potassa, sugar and caustic potass, zinc, iron, caustic lime and rosin, a mixture of caustic lime with charcoal, and charcoal alone, found the last mentioned the surest, simplest, and most economical. Two parts of chloride of silver and one of damp powdered charcoal are mixed and pressed into a black lead crucible, which is then covered with a piece of tile; during the calcination a hydrochloric acid gas is given off; after this ceases, the calcination is continued from 15 to 20 minutes. A carbonaceous mass results, from which the silver is dissolved by nitric acid of sp.-gr. 1.20, and gently heated towards the conclusion of the operation. The charcoal powder is not washed too long, as the last portions of silver adhere so obstinately to it that an inconvenient quantity of water would be required. The remaining charcoal, which still contains some chloride, must be dried and preserved for the next operation. The impurities of the solution of silver are insignificant, and may be diminished by employing lamp-black. To obtain the silver in the metallic state the crucible must be heated much higher. The author attributes the production of hydrochloric acid to the combination of the hydrogen always present in charcoal with the chlorine. * Buchner's Repertorium. SEPARATION OF NICKEL AND BY PROFESSOR WÖHLER. IN Professor Liebig's mode of separating nickel and cobalt, by pouring the two metals into potassio cyanides, and precipitating the nickel by means of peroxide of mercury, protonitrate of mercury may afterwards be employed for precipitating the cobalt, and ascertaining its weight in a direct manner. The liquid from which the nickel has been precipitated by peroxide of mercury, and which contains the cobalt in the state of cobalto-cyanide of potassium, is carefully neutralised with nitric acid, and a solution of protonitrate of mercury, as neutral as possible, added. All the cobalt is precipitated as cobalto-cyanide of mercury, in the form of a dense white precipitate, which is readily filtered and washed. It then requires only to be heated in the air to convert it into black oxide of cobalt. II. CHEMICAL MANUFACTURES AND AGRICULTURAL CHEMISTRY. PHOTOGRAPHIC INVESTIGATIONS.† | lose any of their qualities after an indefinite BY M. BLANQUART EVRARD. I HAVE the honor of submitting to the Academy Photographic proofs on paper, obtained by means of a matrix of albumen. The idea of employing albumen, rendered sensible to the action of light by mixing it with aceto-nitrate of silver, and spread in a fine layer on a plate of glass, belongs to M. Niepce, of St. Victor. It is the most complete confirmation of the principle of the deep impregnation of papers by the photographic substance, a principle which I had laid down previously in a communication to the Academy. "The deep impregnation of the chemical elements in the paste of the paper," 1 said then, "in such a manner that this paste becomes a medium in which may be accomplished the chemical re-actions which finally constitute the photographic image, is a consideration most essential to the success of the operation." (Comptes Rendus de l'Academie, vol. xxiv., 117.) In proposing to substitute for the paste of paper a completely transparent and solid body which might contain the chemical elements, M. Niepce, of St. Victor, opened a new view to photography on paper. Responding to the appeal which he made to experimenters for arriving at practical results, I now submit to the Academy a method which combines all the conditions necessary for the industrial application of photography: for the matrixes on glass, by the preparations obtained on glass which I am about to describe, are unalterable in the light, do not * Annalen der Chemie und Pharmacie. + Comptes Rendus, No. 8, 20th August, 1849. number of drawings, are susceptible of being reconstituted, if accidentally lost, provided that we have a single proof of the lost matrix, and, finally, at all times, in all temperatures and conditions of light, they give satisfactory results. As to the quality of the proofs, I propose to send successively to the Academy results to obtain its opinion. I now confine myself to those which appear to me necessary for proving that photography is capable of the production of models, in the very characters of those models: thus, I now present the proof of a miniature portrait produced, of the same size as the original, and in the light and transparent conditions of this sort of painting; a proof after an oil painting in opposite characters, vigorous shades and brilliant lights; a view from nature, with figures (white cows); and a bronze statue of remarkable finish and model; and, lastly, a copy from an engraving of the same dimensions, uniting, notwithstanding this great difficulty, delicacy, model, and vigor. The following are the preparations :— Collect in a deep vessel a certain number of whites of eggs; remove every thing solid or not transparent; avoid also all dust, which would cause stains. Add 15 drops of a saturated solution of iodide of potassium. Beat up the eggs into a snow, and allow this snow to to rest until it resumes the liquid state. Clean the glass to be used with alcohol, place it on a support, and pour on it a sufficient quantity of albumen. Spread this albumen over the surface of the glass, using for this purpose a piece of glass, in such a manner that its cut side remains in contact with the surface of the glass. Give it several coats. This operation has for its object to put the albumen in perfect AGRICULTURAL CHEMISTRY. contact with the surface of the glass, so that The albumen being well dried on the glass, Glasses thus prepared are photogenic; they may be employed indifferently in the humid or the dry state, if in case of having to operate at a distance or on a journey. In the same way, the proof may be produced after exposure to the camera obscura, either immediately or on return from a journey. This operation is practised, as I indicated for paper in my communication of November, 1847, by plunging the glass in a bath saturated with gallic acid; however, to give to the proof all its value, it is advisable to add to the bath a little aceto-nitrate of sil ver. It will be prudent to take the proof out of the gallic acid before its various parts have acquired the desired tone; for, if the action were pushed too far we could not weaken the too-deep tones which they would present, whilst, if its shades were too weak, we might, without inconvenience, submit it again to the action of gallic acid, even should the matrix have served for producing a great number of proofs. After this operation the glass should be washed in a large quantity of water, and afterwards passed into a solution of bromide of potassium (30 grammes in 100 grammes of water), then washed again in a large quan tity of water, and finally dried by keeping it Thus treated, the albumen acquires on the The positive proofs were obtained in the same manner as the clichés on paper. IMPROVEMENTS IN MANUFACTUR- THE patentee commences his specification The invention consists in the manufacture in the proportion of 1 lb. of pure chloride of lead to 1 cubic foot of water. As some water contains earthy salts (sulphates or carbonates, or both) which precipitate lead, the patentee prefers to use such an excess of chloride of lead as will compensate for this loss. The solution is prepared by introducing the chloride of lead and boiling water into a wooden barrel, provided with a revolving agitator, and then it is run into cisterns to settle. The clear solution of chloride of lead is mixed while still warm (because if allowed to become cool it would deposit some of the chloride of lead) with an equal bulk of the lime-water; on this taking place, the insoluble oxychloride of lead is immediately formed and speedily settles to the bottom of the cistern, leaving a clear supernatant liquor (a weak solution of chloride of calcium); and after this liquor is drawn off the precipitate is collected and dried. solution of each of known strength, and to use it with chloride of lead in the same manner as the lime-water.-Sealed February 14, 1849. INVESTIGATIONS ON THE NATURE OF THE MINERAL SUBSTANCES NECESSARY FOR THE DEVELOP. MENT OF A VEGETABLE.* BY THE PRINCE OF SALM HORSTMAR. THE Prince communicates the result of some interesting investigations which he undertook concerning the inorganic substances which were necessary for the development of a plant. To determine these mineral substances with accuracy, the first condition necessary to be fulfilled was to find a medium which was perfectly free from inorganic matters in which seeds might be made to germinate. The author fixed on the charcoal arising from the calcination of the purest and As the operation of mixing the lime-water and the solution of chloride of lead requires to be performed in an instantaneous manner, the patentee prefers to employ for this pur-whitest sugar-candy. This charcoal had been pose two tumbling-boxes, of about 16 cubic feet capacity, which are charged with the two liquids, and simultaneously upset into a cistern, in which the oxychloride of lead is instantaneously formed, and from which the mixture flows into other cisterns when the oxychloride subsides, The patentee states, that although he has only mentioned pure crystallised chloride of lead in the description of the process, yet it is not absolutely necessary that it should be in this form; for a rough chloride, made from lead ore, and its equivalent of muriatic acid, boiled to dryness, will answer, provided it be well washed, to free it from chlorides of iron, manganese, or other bodies likely to injure the color of the oxychloride. The exact proportion of pure chloride contained in the rough chloride should be ascertained previous to use, in order that the proper quantity may be mixed with the lime-water. If, however, a solution of chloride of lead of uncertain strength is obtained, or lime-water not quite saturated, they can be used with but little disadvantage, for it is only necessary to be careful not to add an excess of lime (i.e., not more than the half equivalent), which can be easily ascertained after a few trials by filling the lime or lead tumblingbox more or less with its respective solution, as the trials may direct. The patentee says, that it will not be necessary to describe any particular mode of proceeding with soda, potash, ammonia, or barytes, for if ever it should happen that these bodies could be used in preference to lime, it would be merely necessary to make a prepared on a porcelain plate, placed in the muffle of a reverberatory furnace, which was safe from the introduction of cinders. The product was powdered and calcined a second time before being used, in order to destroy all traces of carburets of hydrogen, which are prejudicial to vegetation. The author used oats in all his experiments, and this selection was made on account of the importance of the plants belonging to the family of gramina, and of the fact that, even in a room, the oat gives ears capable of ripening. The experiments were made in tin vessels of 5 inches high, 2 inches broad at the top, and at the bottom. These vessels were covered on the inside with white wax, to preserve the roots from contact with the metal. Into each of these vessels was introduced 75 grammes of sugar charcoal, with which was mixed the mineral matters whose influence on vegetation it was desired to study. In order to mix uniformly the small quantities of insoluble mineral matters with the charcoal, they were first triturated with a little charcoal, and then this mixture was added to the rest of the charcoal, stirring the whole in a capsule. The soluble substances were dissolved in 20 grammes of water, and the charcoal was impregnated with this solution. When 0.1 grammes of nitrate of ammonia was employed as a manure, 15 grammes of water were added, because the utility of this excess of water had been demonstrated by previous experiments. When * Journal für Praktische Chemie, xlvi., 193. |