noxide of manganese, and many other natural oxides of manganese, but also that these substances are remarkably well adapted for use in all cases where ozone would be effective as an agent of disinfection. The following reactions have been determined by Valmagini: 1. Ozone test-paper, prepared with starch and iodide of potassium, is immediately rendered blue without the addition of an acid. 2. A solution of chemically-pure iodide of potassium is immediately decomposed by fragments of the mineral, and the separated iodine can be detected by starch or bisulphide of carbon, or by volatilization. 3. Artificially-prepared, chemicallypure binoxide manifests precisely the same reactions. 4. The powdered mineral strewed upon chemically-pure silver, and moistened, immediately produces a brown stain of oxide of silver, as is shown by its disappearance on ignition. 5. Air becomes ozonized by passing over the mineral, or surfaces coated with its powder. 6. Tincture of guaiacum is turned a deep blue by these manganese minerals. 7. Gases resulting from putrefaction are also rapidly destroyed by them. A number of possible sanitary applications of these minerals are suggested, among them the coating or plastering of sewers, or smoke and gas flues, the treatment of waste-water pipes, and use in manufactories, stables, cellars, etc.

New Disinfectant.-A new disinfecting compound, known as the "Universal Disinfecting Powder," is highly commended in the chemical journals. It consists of Cooper's salts and sulphate of zinc. It has been analyzed by Prof. Wanklyn, who reports upon it as follows: "This powder contains 70 per cent. of mixed chloride of sodium and chloride of calcium, and about 6 per cent. of anhydrous sulphate of zinc (equal to about 12 per cent. of hydrated sulphate), a little insoluble matter, and 15 per cent. of moisture.

Spontaneous Combustion of Coal. - The British Government commission appointed to inquire into the spontaneous combustion of coal in ships has made its report—a document of very considerable practical interest. In this report the development of heat in coal-cargoes is attributed to chemical changes which certain substances undergo through the agency of atmospheric oxygen.

The best known of these substances are combinations of sulphur and iron, known as iron pyrites. The presence of moisture in the air promotes the oxidation of pyrites; it does so apparently by bringing the atmospheric oxygen into more intimate contact with the surfaces of the oxidizable material. The oxidation of pyrites is accompanied by the development of heat, which may accumulate to such an extent as to lead to ignition.

But there is another cause of ignition. Coal varies considerably, not only in chemical composition, but in structure, some varieties being comparatively open and porous, others compact or laminated, very frable and readily broken up. Carbon in a finelydivided or porous condition has the property of absorbing and condensing within its pores large volumes of certain gases, among which is oxygen. The condensation of a gas by a porous body is at

tended by the development of heat. Moreover, the tendency to oxidation, which carbon and certain compounds of carbon possess, is favored by the condensation of oxygen within their pores, whereby the very intimate contact between the carbon and oxygen particles is promoted. Hence the development of heat by absorption and the establishment of oxidation occur simultaneously. Oxidation is proceeds so energetically that the carbon may be accelerated as heat accumulates; chemical action heated to igniting point. The breaking up of the coal before and during shipment by the rough usage to which, for the sake of speedy loading, it is often subjected, obviously favors the absorption of oxygen and increases the tendency to heating by this process. The second process is not, like the first, facilitated by moisture. On the contrary, the wet fills up the pores and diminishes the power of absorbing oxygen.

hold of a ship, will accumulate an amount of heat In a tropical voyage, coal, confined in the close which no practicable ventilation will suffice to remove. "Such circulation of air as may be established, even in the less compact portion of the cargo, is not likely to have any valuable cooling effect, and the circulation, if there be any, must be very feeble among the more closely-lying masses of small coal; so that heat, if developed in these, will accumulate undisturbed." Indeed, its development would be favored by the fresh supply of oxygen which a gradual replacement of the air surrounding those reached sooner or later when the development of parts would convey, "so that a period would be heat would be most seriously promoted by ventilation." Thus the commissioners found that the calamities occurred chiefly in tropical voyages. They also ascertained that the percentage of loss increased with the amount of the cargo.

The commissioners found it generally recognized in the trade that the breakage of coal was an evil to be guarded against. Their conclusion is that the machines known as "tips" and "spouts " conduce loading by hoist or by crane the fall from the bottom most to the breakage of the coal. In the system of or end of the wagon into the ship's hold is as great as from the mouth of the shoot or spout; but the coal, until released from the wagon, is literally undisturbed, and the fall from the bottom or end of the wagon, as the case may be, into the spout, together with the concussion of the coal in its passage down the spout, is avoided. Even in this system, however, the fall of the coal first put on board is in deep ships very considerable. To obviate the breakage consequent on this fall, anti-breakage boxes were introduced. The Peninsular and Oriental Company. among others use the box or barrow system. It had been noticed by witnesses examined that the burnings of ships often commenced under the main hatch; but the principal objection of ship-owners value of the cargo. It is now found that the breakto the breaking of coal was that it diminished the age is unprofitable and dangerous.

The commissioners observe that there is a very common confusion between explosions and spontaneous ignition. Explosions are never spontaneous. The gas which causes explosions in mines or on ships is marsh-gas-light carbureted hydrogen. When mixed with a considerable volume of air, it forms a compound which will explode on contact with flame. If coal, from seams which are charged with marsh-gas, is placed on board ship shortly after being raised from the pit, there is obviously great liability to the formation of an explosive atmosphere in the hold or bunkers. Dr. Percy and Prof. Abel observe in their paper appended to the report: "Every possible means should in such cases be had recourse to for facilitating the escape of gas from coal into the open air. But, as the gas requires a large admixture of air to render it violently explosive, it is obvious that any attempt to

solution of iodine corresponding to 0.1 gramme of tannin must be deducted the volume of the solution required to produce the colored reaction upon starched paper. For this purpose 10 c.c. of distilled water are measured out, mixed with 2 c.c. of alkaline solution, and the solution of iodine is then added, drop by drop, till a spot is obtained upon the starched paper. With a solution containing 4 grammes iodine per litre the correction is generally 0.1 c.c. for a volume of 10 to 12 c.c., but the greater or less purity of the carbonate of soda may make a slight variation in this correction. To 0.01 gramme of tannin dissolved in 10 c.c. of water it is generally necessary to take 10.5 c.c. of a solution at 4 per 1,000. The paper used is white filter-paper, covered by friction with a slight layer of powdered starch. For ordinary determinations tannic acid may be taken as the type of the active principle of astringent bodies. But, if a high degree of accuracy is required, the solution should be standardized with a pure sample of the astringent body under examination, catechuic acid being used in case of catechu, morintannic acid for fustic, etc. Crystalline gallic acid decomposes the solution of iodine in the same proportion as tannic acid. If it is desired to determine these acids separately, we first find the joint amount of tannic and gallic acids, and then, operating on a fresh portion, remove the tannic acid by means of rasped hide or gelatine and alcohol, and determine afresh the gallic acid remaining. The tannic acid is then found by subtracting the second result from the first. The extractive matters found in astringents do not interfere.

Coffee Adulteration.-Prof. G. C. Wittstein, in an article contributed to Dingler's Polytechnisches Journal, and translated by Carl Bauer for the American Chemist, discusses the subject of detecting adulterations in coffee. According to the author, masses of dough, moulded after the true bean, are sometimes sold for coffee. Unlike the genuine, these fictitious beans always have sharp edges, and may be very easily ground to a grayish-yellow powder. Boiling in water reduces them to a pasty mass, which, on addition of iodine, assumes a deep-blue color. The poorer classes of genuine coffee-beans are variously treated, so as more or less to resemble the better grades. Thus, the coffee is placed, with a quantity of shot, in a barrel, which is rolled about until enough lead has been rubbed on the beans to give them a glossy appearance. This adulteration can be detected by the use of a lens; but, when absolute certainty is desired, the beans should be digested in dilute nitric acid; then the liquid should be decanted after one hour, diluted with three times its volume of water, and the lead precipitated with sulphureted hydrogen.

Another substance for coloring coffee is a greenish powder, 100 parts of which are composed of 15 parts Prussian blue, 35 parts chromate of lead, 35 parts of a mixture of clay and gypsum, 15 parts water.

The microscope alone is frequently sufficient te discover this adulteration. For more accurate examination, however, it is better to put a considerable quantity of the beans in a suitable vessel, and to pour distilled water upon them. After two hours or so, the beans are removed and the turbid liquid allowed to settle. In presence of gypsum the superaddition of barie chloride and ammonic oxalate. natant clear liquor will become densely turbid on Prussian blue may be detected in the sediment by giving rise to a brown coloration on addition of KHO. If this change of color should not occur, the mixture will not contain Prussian blue, but probably indigo. The color of the latter may be destroyed by nitric acid. The potassic hydrate will likewise de compose the plumbic chromate, to a greater or less extent, causing it to dissolve partially or wholly in the alkali. Turmeric, if present, would merely turn dark brown. If, upon slightly moistening the sediproduced, no further doubt need be entertained as ment with sulphide of ammonium, a black color is to the presence of chrome-yellow in the mixture.

By the process of roasting, coffee is put into a condition which renders adulteration almost impossible, so long as the beans remain unground. Ground coffee is one of the easiest substances to adulterate. The most usual adulterants are chiccory, beans, peas, as also beets, carrots, and other roots resembling the turnip in properties.

As all these preparations undergo the same treatment as pure coffee, namely, of roasting to a deepbrown color, in many particulars they resemble the genuine article very closely. They cannot, however, be used as a true substitute for the latter, as all are without the most important constituent of pure coffee, namely, caffein.

suspected coffee is poured out on water. If pure, The following is a very convenient test: The the particles will float and remain in a state of suspension for hours; whereas chiccory will sink im mediately. A better method is as follows: If to 30 drops of the coffee decoction, in a test-tube, 2 drops of concentrated hydrochloric acid be added, and then, after a few seconds' boiling, the liquid be treated with 15 drops of a solution of 1 part red prussiate of potash, and 8 parts of water, and again boiled as before, the liquid will first turn green, finally blackish green. Upon now adding to the mixture 6 drops KHO, the liquid, after minute's further ebullition, will become brown, and shortly after, with the deposition of a dirty-yellow precipítate, clear, pale yellow. If the chiccory decoction is subjected to the same treatment, the last liquid will be brown and turbid, and only after long standing will a precipitate be deposited while the supernatant fluid retains its brown color. By testing in the same manner a mixture of 6 drops of chiccory and 24 of coffee, the brown turbidness will also be obtained. It is thus easily possible to discover adulterations of chiccory in coffee.

The quantity of coffee actually dissolved in a decoction is perhaps always overrated. A good, by no means weak, infusion, left upon evaporation' a resi due of 1 per cent., and a very strong infusion scarce y 2 per cent. This residue has the appearance of a dark-brown shining varnish, which is scarcely hy groscopic, at least remains dry after two days' exposure. If, however, the coffee contains one of the artificial preparations above referred to, the residue will become sticky to the fingers within 2 hours, and ple process may likewise be used as a test upon sus will, after 24 hours, be decidedly moist. This sim pected coffee. Even the impurity in coffee, chiccory, is subject to various adulterations: among others with bog-turf. According to Prof. Th. Schwartz, of Ghent, this fraud is practised to a considerable extent, especially in Flanders.

Antiseptic Properties of Boracic Acid.Prof. Mauricio Schiff, of Florence, after ex

amining and tasting numerous samples of meat, prepared in many different ways, and preserved, by Herzen's method, for months at the summer temperature of Florence, declares that no trace of putrefaction could be detected, nor could any indications whatever of change be found with the aid of the microscope. Remnants of a large quantity of meat, packed without special care in tin cans, that had been carried on two tropical voyages, proved palatable after a year, and two of his friends subsisted upon meat put up in this way for a month. A solution of crude boracic acid in water, to which borax has been added, to render it more soluble, is employed in the process. The effect of the solution is also heightened by the addition of salt and saltpetre, which tends to preserve the original fresh appearance of the meat. Chemical Production of Cellulose.- A method of producing cellulose by chemical processes, for paper manufacture, has been patented by Dr. Mitchelich, of Darmstadt, the peculiarity of which is, that the incrusting substance of the wood is not destroyed, but merely separated from the cellulose and made soluble, the original texture being left intact. Hence, in this process, it is not necessary, as in others, to divide the wood finely; a breaking up into pieces like those of domestic fire-wood is sufficient. In the process itself, a lime solution is used, which is boiled with the wood some 6 hours, at a pressure of 3 atmospheres. After boiling, the incrusting matters are found partly dissolved in the liquid, partly in the pores of the wood, from which latter they can be easily removed by squeezing apparatus. Where a very valuable white paper material is wanted, not in need of bleaching, whitish woods, as free of resin as possible, must be used, such as poplar, willow, or lime. The success of this process depends much less on the pressure in boiling than on the temperature, which must not rise above 120°. The use of oak-wood offers the advantage that the contained tannic acid is obtained as a by-product, that may be employed in tanning.

New Test for Alcohol.-While making some experiments on molybdic acid, Dr. E. W. Davy observed that, when a solution of that substance is brought in contact with alcohol, a deep azure-blue color is developed; and, as the protosulphate of iron and the protochloride of tin, two powerful oxidizing salts, produce a like effect on the solution, there is little doubt that it is due to the deoxidizing action of alcohol. This reaction of alcohol on the molybdic solution is extremely sensitive; thus, if one part by volume of commercial rectified spirits be mixed with 100 parts of distilled water, and one drop of this mixture brought in contact with it, a deep-blue coloration is at once developed.

Though small quantities of spirit, even when considerably diluted with water, will produce with the molybdic solution the blue reaction without the assistance of any external heat, still, where very minute quantities, diluted with such large proportions VOL. XVI.-7 A

of water as those just stated, are to be detected, it is necessary, for the success of the experiment, that also that too great a dilution of the test-solution the reaction should be assisted by a gentle heat, and with the liquid under examination should be avoided, as the blue coloration will not be developed if water be in excess; and, even after it has been produced, the addition of a certain proportion of that being the case, the best way of employing the test substance quickly causes its disappearance. Such is to place three or four drops of the molybdic solution in a small, white, porcelain capsule, and, having heated them slightly, allow one or two drops of the liquid to be examined to glide or fall gently on the immediately or after a few moments, the blue coloracid solution, when there will be developed, either ation. And, where the alcohol is very largely diluted with water, it is better to continue the gentle heating of the test solution for some time, to concentrate it adding the liquid to be tested; for, in this way, the or expel as much water from it as possible, before author has succeeded in detecting the spirit in mixtures so dilute as to give no blue reaction when added immediately to the test solution on its being the temperature of the acid solution must not be simply warmed. As regards the application of heat, raised too high, for, if it be heated till the acid evolves its dense vapors, or begins to boil, the solution will of itself alone, from its partial decomposition, develop more or less blue coloration, which will become more perceptible on its cooling. But such water-bath as the heating agent. an occurrence can be easily avoided by employing a

But the coloration produced in the reaction stated disappears after a variable interval of exposure to the air-a circumstance which is due to the absorpreoxidation of the molybdenum compound, as might tion of moisture from the atmosphere, and not to the have been supposed.

The reaction is not peculiar to ordinary or ethylic alcohol, but is more or less readily developed by others at least the author found it to be so in the hols, those being the only ones he had for his excase of methylic, propylic, butylic, and amylic alcoperiments. But it is more than probable that some at least of the other alcohols may act in a similar manner; however, the reaction is much more rapid and striking in the case of ethylic than in that of any of the other alcohols mentioned.

This test is of especial value for determining the purity of chloroform and chloral hydrate, one of the common impurities of the former being ethylic alcohol, and of the latter chloral

alcoholate.

Extraction of Iodine from Seaweed.—Mr. Thowald Schmidt, of Aalborg, Jutland, has devised the following new method of obtain ing iodine, potash-salts, and other commercial products from seaweed: After the seaweed is dried and burned, a concentrated solution of the ash is added to the liquor containing chlorides of sodium and calcium, left after the ammonia has been recovered in the ammoniasoda process by boiling with lime. The sulphates of potash, soda, and magnesia contained in the ash of the seaweed are thereby decomposed, and hydrated sulphate of lime and hydrated magnesia are precipitated in a form which may be available for paper-making as "pearl-hardening." The last traces of sulphates are got rid of by adding a small quantity of solution of chloride of barium. To the clear solution nitrate of lead is now added until all the iodine is precipitated as iodide of