Imagini ale paginilor

constituents of a gaseous mixture, converting each into a solid or liquid form, in which condition they can be weighed on a balance. Professor Wurtz alludes in his memoir to the fact that gravimetric methods for gas analysis were successfully employed by chemists some thirty years ago, and expresses his surprise that so little has been done to de. velop their capabilities. The general outline of his method is about as follows: In a crude coal gas, as drawn from the hydraulic main, the gas-chemist should be able to separate and deternine with precision the following: (1) Tar, suspended in the form of spray; (2) Water, do. ; (3) Water, as vapor, dissolved in the gas; (4) Naphthaline (condensible); (5) Other condensible hydrocarbons; (6) Smoke and soot (with dust); (7) Ammonia; (8) Carbonic acid; (9) Sulphureted hydrogen; (10) Carbonic oxide; (11) Oxygen (intermixed air).

Of these eleven proximate constituents, Professor Wurtz affirms that he has succeeded in separating with very satisfactory sharpness Nos. 1, 2, 3, 6, 7, 8, 9, and 11, eight in all, besides approximating to No. 4 the naphthaline in excess. Nos. 5 and 10 are still subjects of experiment. The following are the devices and manipulations employed : First. Arresting suspended matter by means of empty dry flasks, and straining through cotton previously desiccated. Absorbing next the ammonia, by means of re-agents which act on no other ingredient. Next, drying the gas with calcium chloride, which, ammonia being absent, may now be done. Next, taking up the sulphureted hydrogen by a normal metallic salt, so selected or so managed as to give up no water or acid vapor to the desiccated gas. Next, using sodic hydrate to absorb the carbonic acid, with certain precautions. Next, alkalized pyrogallol, or other suitable agent, to absorb oxygen, arranged so as to lose no water. The final (rough) measurement of the gas is then made at an observed temperature by a gas-meter. The whole process is finally completed by a process of distillation, either at the ordinary or higher temperature in a current of the same gas analyzed, that has been subjected to similar treatment, and thus freed from all the ingredients to be separated from each other. After final weighings, the correct initial volume of the gaseous mixture is calculated from certain formula derived from the crude meter-indications and the final weighings. For further details, we refer our readers to the memoir in full (vide Journal of the Franklin Institute, Vol. LXIX., p. 146 et seq.).

Schering affirms that the burning of glycerine may be readily effected in any form of lamp which permits the flame to be brought directly above the surface of the combustible. A long wick will not afford a steady flame, because of the sirupy consistency of the glycerine. The flame of glycerine is, like that of alcohol, very slightly luminous; and as the latter is of great utility as a solvent, Schering was induced to experiment with the glycerine flame, with the view of substituting the latter for the alcohol flame for laboratory and other purposes. The results obtained were quite satisfactory.

The assertion of Raoult, that pure cane-sugar in aqueous solution, and with the complete exclusion of air and ferments, would gradually undergo inversion under the influence of light, has been called in question by Kreussler, who has repeated the experiment with every possible precaution. The last-named chemist asserts that a pure sugar solution, kept in glass tubes, the open ends of which were drawn out and sealed with the blow-pipe, after the air contained therein had been completely driven out, failed to respond in the slightest degree to Fehling's test for glucose. Where the air had not been completely excluded, however, the contents of the tubes upon examination indicated the conversion of from 52 to 90 per cent. of the cane-sugar


grape-sugar. Albumen for printing purposes is said to be becoming scarce, and a new source of supply is greatly needed. The debasement of silks by foreign admixture, if we may infer from the comments of journals devoted to textile interests, has of late reached such a height as to promise shortly to rival that of a class of cotton-goods which have added largely to the notoriety, if not to the fame, of one of the manufacturing centres of England. A writer to one of the French journals shows that the weighting of black silks—which began with the modest aim of making up for the loss sustained in ungumming-is now carried to the extent of 100, 200, and 300 per cent. This increase of weight is effected by treatment with salts of iron and astringents, salts of tin and cyanides. The bulk is augmented proportionably to the weight. The same writer points out very clearly the evils attending this excessive adulteration. The chemical and physical properties of the silk thus treated are materially modified. What is sold as silk is, in reality, a mere agglomeration of heterogeneous matters devoid of cohesion, held together temporarily by a small portion of silk. The strength and elasticity of the fibre are likewise reduced. From being in its natural state one of the most stable of substances, and but slightly combustible, in its adulterated state it burns like tinder if touched by a flame. It is likewise affirmed to be liable to undergo spontaneouis decomposition, and to absorb gases with the evolution of heat which sometimes leads to actual combustion. The adulterated silk when burning scarcely gives off the characteristic odor of animal matter.

It is of interest to supplement our notices in last year's Record of the artificial production of vanillin--the active principle of the vanilla bean (which is now a commercial operation)-by reference to a suggestion for obtaining it largely by another process. In several manufacturing operations pine-wood is treated in iron boilers, under high pressure, with a solution of caustic alkali. The resulting liquid contains various salts of soda, and, if the temperature has not been too great, among them the soda salt of vanillin. Experiments made with the view of establishing this fact are conclusive, its presence being demonstrated by the presence of an intense vanilla odor, which becomes more prominent when the liquid is treated with an acid and left standing for several days. It has thus far, however, been found impossible to extract the crystallized vanillin from the above-nained liquid, though in all likelihood this consummation will not be long delayed.

M. Gerard gives the name of Apparatine to a colorless, transparent substance which he obtains by heating starch, or substances rich in starch, with caustic alkali. The product resulting from this treatment is said to be excellently adapted as a dressing for all kinds of textile fabrics--cotton, woolen, or silk--to which it imparts a velvety gloss impossible to obtain by any other mode of treatment.

M. Paulet's observations upon the chemical operations involved in the preservation of timber, contribute materially toward the rational explanation of conflicting and often contradictory results obtained in practice. This author's investigations-lately placed before the French Academy-were devoted specially to the examination of the destructive action which takes place in wooden railway sleepers injected with sulphate of copper. It is generally held that the protective action of metallic salts is due to their combination with the ligneous tissue, and especially with the nitrogenous matter, which is rendered insoluble and poisonous to living beings. This operation the author claims to be insufficient. He affirms, from his studies of the action of metallic salts, and especially of sulphate of copper, upon the nitrogenous matter of wood, that the albumino-cupric precipitate is not absolutely insoluble in water, and that it is especially soluble in water containing carbonic acid. The nitrogenized matter in wood is partly soluble and partly insoluble. The soluble albuminous portion is fixed by the metallic salt, which combines also with the insoluble nitrogenous matter. The water, especially if charged with carbonic acid, destroys and removes this metallic compound; in proof of which the author gives a number of examples, which show that the copper gradually passes out of the combination and disappears altogether, giving place to the carbonate of lime. The process is explained to be as follows: The carbonate of lime contained in the ballast is slowly dissolved under the influence of the rain-water, and penetrates gradually into the wood, substituting the copper. So long as the copper remains in its original combination, its preservative action continues. The carbonate of lime is not a septic agent, but it eliminates the preservative body from its compounds, and restores the matter to be preserved, if not to its natural state, at least to one which facilitates the access and the action of destructive agents. This theory is confirmatory and explanatory of the fact, long established by observation, that railway sleepers, etc., are destroyed most rapidly in calcareous soils; and the affirmation of the imperfect insolubility of the albumino-metallic precipitate, is additionally confirmed by the fact that the injection of timbers with metallic compounds has been found to afford but little protection to the same where they are immersed in fresh or salt water. Some further comments on the methods of injecting timber with preservative compounds will be found under the department of General Technology,

It is of importance to record that Coupier's process for producing aniline colors without the employment of arsenic is being largely introduced. It appears that Coupier some time ago succeeded in producing fuchsine by the action, at à suitable temperature, of hydrochloric acid and iron in small quantities on pure aniline and nitrotoluol. Although it was demonstrated that the aniline red obtained by this method was identical with that usually manufactured, and that the yield was greater than where arsenic acid was used, the process was until lately very sparingly introduced on the commercial scale. Recently, however, we learn, the Gesellschaft für Anilin Fabrikation of Berlin has erected new works, where no arsenic acid is used in the preparation of colors. Not only fuchsine, but all the colors derived from it, are made, and all are warranted to be free from this poisonous agent. The company is producing from 200 to 300 kilogs. per diem, and the product is affirmed to be not only purer, but stronger than that made from arsenic acid. Being entirely free from this poisonous substance, these dyes are suitable for a great variety of industrial uses where the others have been found to be dangerous. Upon this subject the Chemical Neros expresses the hope that, the commercial success of the innovation being demonstrated, other manufacturers of these dyes will adopt the new method, and relinquish the old arsenic-acid process, which, apart from the inconveniences it has caused both manufacturers and consumers, has led to many lamentable accidents.

Eosin (from čwc, daun) is the name by which a newly introduced dye-stuff has been designated. In its solutions and upon silk it is characterized by exhibiting a gorgeous fluorescence, in which the beautiful tints of rose and garnet red predominate. It is brought into commerce in the form of a brown red powder, with a greenish, metallic sheen. It is soluble in water and in alcohol.

Delachanal and Mermet have devised a lamp for photographic purposes which effects the continuous combustion of carbon-disulphide and nitrous oxide. Riche and Bardy have investigated the photo-chemical intensity of various flames,

[ocr errors]
« ÎnapoiContinuați »