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Henry E. Roscoe states that although his method of measuring the varying intensity of the chemically active rays as affecting chloride of silver paper has been the means of pointing out many important facts, yet it has not been introduced as a regular portion of the work of meteorological observatories; until wbich is done we can not hope to obtain any thing like a complete knowledge of the laws of distribution of the chemical rays over the earth's surface. This neglect of Roscoe's method is, in part at least, due to the labor of observing. He has, therefore, advised a modification of the instrument described by him in 1865, and as thus modified the constant sensitive paper is exposed to the action of total daylight at given intervals, say at every hour during the day, by a self-acting arrangement for accurately noting the times. These hourly records are then read off in the evening by the observer. Many mechanical difficulties have been overcome through the skill of Mr. Jordan, of Manchester, and the instruments, as described by Roscoe in the last volume of the “Transactions of the Royal Society of London,” are said to give complete satisfaction, In order to read off the intensities of recorded photographic images, a standard series of graduated tints is provided. Special directions are given for the preparation of the sensitive paper. The correction due to the reflection and absorption of the glass cover is also investigated; and the comparison of observations made by hand, and by the self-recording instrument, over twenty days with the two methods, closely agree.-Philosophical Transactions, London, 1875, 655.


The presence of a considerable amount of chloride of antimony was demonstrated several years ago, by Professor Böttger, in the so-called explosive antimony formed on the negative pole, consisting of fine platinum wires, the positive one being of massive antinjony, when the current of a single

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Bunsen element is passed, for three or four days, through officinal solution of terchloride of antimony, with a resistance of about eight hundred feet of copper wire in the circuit. He has recently also detected occluded hydrogen in it, possessing identical reducing properties with the hydrogen absorbed by palladium. Thus, if the platinum wires, covered with recently deposited explosive antimony, are placed in a very dilute aqueous solution of ferricyanide of potassium, the partial conversion of the latter into ferrocyanide will be evident in the course of ten or fifteen minutes. Pure antimony, perfectly free from arsenic, will not produce such a result. Since the liquid employed is a hydrochloric-acid solution, the liberation of gaseous hydrogen at the negative pole, with the antimony, by decomposition of the acid, might be expected, but not the slightest trace of it could be detected, while, on the other hand, the presence of chlorine at the negative pole, in combination with antimony, without the evolution of hydrogen, is so remarkable that it seems desirable to test other metallic chlorides thus electrolytically.—15 C, XXII., 1875, 337.

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The increased demand for bromine, after the introduction of potassic bromide into medicine in 1866, led to its preparation from the mother liquor at the different salt-works of Pennsylvania, and subseqnently at those of Ohio and West Virginia. The method employed is the usual one with binoxide of manganese and sulphuric acid. From 1867 to 1870 the production increased from 11,000 pounds to 194,000 pounds. Up to 1870 all was consumed in the United States, but since then it has been exported. The price, however, has been so depressed by excessive production that no new works for its preparation are being established. -18 C, February 9, 1876, 95.

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DETERMINATION OF OZONE IN THE AIR. The determination of the quantity of ozone in the air has not yet been achieved by any convenient method, since the tint of the ordinary ozone test-papers is determined by the velocity of the wind. It was supposed by Von Pettenkofer that the absence of the ozone reaction in the atmosphere of closed dwelling-rooms was due to the slight circulation in


the air. This subject has, however, been fully investigated
by Wolffhugel, who finds that, while a given quantity of
fresh air yields a very visible ozone reaction, yet ten or
twelve times that quantity taken from the interior of dwell-
ings produces no effect, even when the rooms are unused,
having previously been well aired. Wolffhugel has also
shown that there is a great absence of ozone in the air near
the ground.—7 C, 11, 122.

Gladstone and Tribe find that when aluminum foil and
iodine are placed together in water, hydrogen is copiously
evolved. The same phenomenon takes place if aluminic io-
dide be substituted for iodine, its formation really being the
first part of the reaction just described. Aluminic bromide
or chloride acts in much the same manner, the aluminum
used being almost completely oxidized. The same experi-
menters sought to determine whether zinc or iron, heated
with solutions of their respective iodides, would yield hy-
drogen, and obtained only negative results. These metals,
however, with aluminic iodide in water, produced readily a
copious evolution of the gas. Aluminum alone decomposes
water, according to Deville, only at a white heat. But
Gladstone and Tribe, by simply coating aluminum foil either
with copper or platinum, procured couples which effected
the decomposition quite easily at the low temperature of
100° Centigrade.—21 A, 822, September, 1875.

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Deville and Debray find that when a mixture of potassium
cyanide and spongy platinum is heated together in the neigh-
borhood of a little water, at about 500° or 600°, a vacuum
having first been established, great quantities of hydrogen
are evolved, and the well-known platino-cyanide of potassi-
um is formed. The hydrogen is not pure, but contains small
quantities of ammonia, and from four and a half to twelve
per cent. of carbonic oxide.—6 B, January 24,


About a year ago Professor Guthrie described under the above name a set of hydrates which exist only at very low

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temperatures. Whenever a crystalline salt is dissolved in water and the solution frozen, solidification takes place below the Centigrade zero, and a definite compound of the water with the salt is formed. And whenever any crystalline salt is mixed with ice or snow, the same compound is formed, and a fall of temperature ensues. Hence with every crystalline salt a freezing mixture may be prepared. Guthrie now extends his observations to colloid bodies, and shows that they act very differently from the crystalloids. Thus from a solution of gum, gelatin, or albumen all the water separates as ice at 0° Centigrade, and no cryohydrate is produced. This new distinction between crystalloids and colloids seems to be of the very highest importance.-1 A, June 30.

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Faulquier narrates a curious phenomenon which took place during the summer of 1875 at Palavas, near Montpellier. In the vicinity of this place are extensive salt marshes, which, in consequence of persistent north winds, have become almost dried up. The accompanying heat of the season has produced a rapid decomposition of the organic matter in the soil, which has been accompanied by a development of sulphuretted hydrogen. The existence of this gas bas been very palpable to the senses, and has also produced an unexpected influence upon the residences near by, the painted surfaces of the houses having first turned brown, and finally almost entirely black, while the paint even in the interior of the houses has become much altered. All silver and silvered objects have also become blackened by the same influences. Another effect is that of loosening and crumbling away of the plaster between the joints of the building-stones, which Faulquier attributes not to the sulphuretted hydrogen, but to the saline particles contained in the atmosphere.—1 B, September 5, 346.

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AMMONIA IN SULPHURIC ACID. Professor F. H. Storer finds that ammonia in traces is an invariable contaminant of sulphuric acid. Nine samples of acid were examined from different manufactories, seven being obtained direct from the makers. These were kept previous to examination in tightly stoppered bottles, and in every case

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the portion tested was taken from the middle of the bottle containing it. The same impurity, ammonia, was also found in a very large number of other chemicals in the preparation of which sulphuric acid is employed. Professor Storer thinks that the ammonia may get into the acid, partly from the air, partly from the water employed, partly from a reduction of the nitric acid used in oxidizing the sulphur dioxide formed in the first stage of the sulphuric manufacture. In fact, he finds by direct experiment that whenever dilute nitric acid is made to act either upon lead or sulphur (as in the leaden chambers of sulphuric-acid works) traces of ammonia are produced.-4 D, December, 1875.

AMMONIUM NITRITE. This extraordinary substance bas been reinvestigated by Berthelot, who obtained it by double decomposition from barium nitrite and ammonium sulphate. The filtered solution, evaporated over quicklime in vacuo, yields crystals of the substance desired. It is also formed by the simultaneous reaction upon each other of nitrogen tetroxide, dry ammonia, and oxygen. It forms a white, crystalline, deliquescent salt, having peculiar elastic properties. It decomposes slowly at ordinary temperatures; at 60° to 70° Centigrade it explodes violently; under a severe blow it detonates. In solution the salt, anomalously, decomposes more rapidly than when dry; heated, torrents of nitrogen are evolved. It seems to be one of the least stable bodies known.-Annales de Chimie et de Physique.

ACTION OF NITRIC ACID ON METALS. The subject indicated by the heading of this paragraph has recently been studied by Mr. J. J. Acworth, who explains some points which have often led to confusing uncertainties. Thus nitric acid, acting in the cold on copper, should yield nearly pure nitric oxide, but does not always. Acworth finds that as cnpric nitrate accumulates in the solution, nitrous oxide begins to be formed; and that when the above-named salt becomes sufficiently abundant the latter gas is given off almost alone. If ammonic nitrate be added to the nitric acid during its action on copper, the gases evolved consist chiefly of nitrogen with nitrous oxide, and

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