tion of the sunlight. This same result can also be witnessed by the passage of clouds between the sun and mirror. The actual direction in the plant is from the apex of the leaf in sunlight and towards it in the shade. This change in direction is so rapid when produced by the shadow of fast flitting clouds across the sun's disc that it would seem that the change of temperature could hardly be felt by the plant; it certainly could not be by an ordinary thermometer; but a heated body properly placed will quicken the circulation, as cold will retard it. If he mistakes not, we have here a fine demonstration of the conversion of light into heat by its passage through the vegetable tissues, and of heat into motion by its action upon the laticiferous vessels.

CHEMISTRY.

How to Test easily the Fatty Oils.-In a paper published in the Journal de Pharmacie for July, Dr. Massie gives a method by which we may readily test the relative value. In order to test the purity of the oils, the author employs nitric acid (sp. gr. of from 1.38 to 1·41) and metallic mercury. Five grms. of this acid, and 10 grms. of the oil to be tested, are mixed together in a test-glass of 100 c. c. capacity, and the mixture stirred for a couple of minutes. The liquid is then left standing; and, when the fluid has separated into two layers, the colour of these layers is noted. This coloration may be from greenish-white to deep brown for the superior, or lighter layer; while the coloration of the acid, always less intense, will vary from light yellow to deep yellow, or even rose-red. After a while 1 grm. of metallic mercury is added, the final result of which addition will be the solidification of the bulk of the oil in most cases.

Alkalinity of Carbonate of Lime.--Mr. W. Skey, who we observe constantly sends communications to the Chemical News, and who is analyst to the Geological Survey of New Zealand, sends an interesting note relative to the alkalinity of carbonate of lime. He gives the results, which seem to show that the salt is alkaline rather than neutral. The following are results of several experiments. 1. Carbonate of lime, prepared by igniting pure oxalate of lime in a close crucible, at a dull red-heat, gives an intense alkaline reaction with reddened litmus-paper, after moistening with distilled water, or after re-ignition with pure carbonate of ammonia. 2. Carbonate of lime, prepared directly from chloride of calcium and bicarbonate of soda, by admixture of their aqueous solutions, and washing the ensuing precipitate till all the soda was removed, gave the same reaction with test-paper. 3. Limestone, shells (calcareous), calc-spar crystals, and arragonite, are all strongly alkaline to test-paper (at least, the samples he had tried were); the powder of any of these substances, washed with distilled water for many days, does not seem to lose any of this alkalinity. Lastly (and he thinks conclusively), precipitated carbonate of lime, prepared by either of the above processes, when agitated with weak hydrochloric acid, in successive quantities, until gradually reduced to a minute proportion of its original bulk, still manifests this reaction to an eminent degree; indeed,

the solution could not be rendered permanently acid till the whole of the carbonate was dissolved.-Chemical News.

Method of Treating Native Sulphides, &c.—The Moniteur scientifique for August contains a paper on this subject, by Dr. E. Kopp. He first alludes to the mineral resources of Italy, which appear to be far greater and of more value than is generally known or suspected. The difficulty of rendering these treasures industrially available is the great scarcity of fuel. Under these conditions, a series of experiments have been made, to ascertain whether it might be possible to apply cheap and readily-accessible chemical re-agents to act upon the above-named minerals (without simultaneously affecting the gangue), so as thereby to render them in a state fit for being readily converted into metals. As reagents available for the purposes alluded to, the author has found common salt, chloride of iron, and hydrochloric acid readily to suit the requirements. Among the practical suggestions found in this paper, is the fact, that the most economical method to extract the small quantity of copper present in previously-burnt pyrites, consists in first exposing the burnt substance for a time to air and moisture, and then to pour over the material a solution of common salt. A small addition of hydrochloric acid is very useful; the copper thus becomes converted into a soluble chloride.

Hydrogenium Amalgam.-A great deal of interest attaches to all attempts with this substance. We therefore give the following account of Dr. Loew's attempts as set forth in the Journal für prakt. Chemie (Nos. 6 and 7). He prepares the hydrogenium amalgam by shaking together, in a vessel to be kept very cool, a mixture of mercury containing from 1 to 2 per cent. of metallic zinc, along with an equal bulk of a solution of chloride of platinum containing 10 per cent. of solid chloride. A slimy mass is obtained, devoid of metallic lustre and prone to decomposition, owing to the presence of some zinc and some compounds of that metal; but, on treating the mass with dilute hydrochloric acid, a body having the consistence of butter is obtained, which, according to the author, is a true amalgam of mercury and hydrogenium.

Calorific Value of certain Gases.—In a paper read before the American Association at Salem, by Professors B. Silliman and H. Wurtz, there are some conclusions which will be of interest to our readers. From the second table it is clear-1. That, of all known gases, the highest calorific effects, under ordinary atmospheric conditions, are obtainable from carbonic oxide, whose calorific value, above 100° C., is about 3,000° C. 2. That, in absolute calorific value, below 100° C., in the atmospheric medium, hydrogen surpasses the volume of any other gas, giving a temperature of about 3,200° C. 3. That for all modes of application—that is, for producing both high and low temperatures-the total maximum calorific effectiveness of carbonic oxide is a constant quantity. 4. Compound condensed submultiple volumes of hydrogen, like that in marsh gas, have much less total calorific value in air than their volume of free hydrogen. 5. Condensed compound submultiple volumes of gaseous carbon, like that in olefiant gas, have no greater total calorific value in air, below 100° C., than their own volume of carbon gas in the form of carbonic oxide; while above 100° C. their value is even considerably less.

Mica a Substitute for Bronze.-The practical value of mica may by this means be much increased, but we doubt the possibility of making it a real substitute for bronze. The following quotation is taken by the Chemical News from the Journal für prakt. Chemie. The mica is reduced to small pieces in a stamping mill, digested with chlorhydric acid, cleansed by washing and sorted by sieves into sizes. The mica scales so prepared have a beautiful vitreous lustre, a silvery appearance, and bear in commerce the name of brocade crystal colours or mica bronzes. The advantages of these brocades over the common metallic ones are-1. They contain no unwholesome substance. 2. They possess a metallic lustre like the metallic brocades, and much surpass them in splendour. 3. Brown, blue, black, green, and red colours of rare brilliancy can be obtained, which is not the case with the metallic brocades. 4. They are not dimmed by sulphur vapours. The analyses by Drs. Cech and Schneider show that the colouring matter of the rose-brocade is cochineal; that of carmine is fuchsine; bright red, fuchsine, and Havanna brown; violet, Hofmann's violet; bright blue, Berlin blue; dark blue, probably impure aniline blue or Girard's violet; light and dark green, a mixture of aniline blue and curcuma; gold, curcuma; silver, the mica alone, &c.

How to Estimate Glacial Acetic Acid Quantitatively.—The Chemical News, quoting from a German journal, says, that F. Rüdorff preliminarily refers to the usual methods of the estimation in question, by means of a titrated soda solution, stating it to be unsatisfactory; and next mentions that his method is based upon the estimation of the freezing-point of the acid in question. The author enters at length into the details of his experiments, the chief point of interest of which is that perfectly pure and anhydrous acetic acid solidifies at 16°-7; that if either water, alcohol, some salts, or sulphuric acid are present, these substances tend to lower the point of solidification, so that 100 parts of the pure acid, mixed with 24 of water, solidifies at -7°.4.

Amorphous Silica for Fixing Dyes.-In Dingler's Polytechnisches Journal· (second number for June) Dr. M. Reimann describes a series of experiments made with the view to apply amorphous silica (as obtained by precipitating a solution of so-called water-glass, silicate of soda, or potassa, with an acid, and collecting, washing, and drying the precipitate in the ordinary way) for absorbing the solutions of fuchsine, aniline blue, &c., and to apply the coloured powder so prepared as a pigment for various materials. The author states that glass, first superficially acted upon by hydrofluoric acid, and next mordanted, as is usual for cotton, assumes, when submitted to the processes in use for dyeing fibre, precisely similar colours as that fibre, and that this effect is caused by the amorphous silica contained in the glass and made active by the hydrofluoric acid.

A Test for Water in Milk.—It is, as is well known, a remarkably difficult matter to detect water in milk, so as to say for certain that it has been added. A test which appears likely has been devised by Dr. A. E. Davies, F.C.S. Such a test, he believes, we have in the specific gravity of the serum, or liquid portion of the milk, from which the caseine and fat have been removed by coagulating and straining. The gravity of this liquid he has found to be remarkably constant, ranging, in that obtained from genuine milk, from 1.026 to 1028; and, by carefully ascertaining the specific gravity

of the serum of genuine milk diluted with various quantities of water, we may obtain a standard of comparison which will enable us to say, within a few per cents., what quantity of water has been added to any sample of milk that may come under our notice.—Chemical News, August 5.

A Simple Experiment in Reduction and Oxidation.-The following experiment has been described in the Berichte der Deutschen Chemischen Gesellschaft zu Berlin, No. 12.-A well-polished small copper bell is placed in a ring on a triangle, and made red-hot by causing a strong gas flame to play upon it, so as to render the metal red-hot, and, consequently, very soon black. As soon as this is the case, a strong current of hydrogen gas is directed upon the metal, by means of a flexible tube fastened to the neck of a glass funnel large enough to cover the bell. As soon as the hydrogen comes into contact with the red-hot metal, the layer of black oxide of copper is removed, and the metal appears as before it was heated. By removing the current of hydrogen, the oxygen of the air again acts upon the hot metal; and thus this alternate oxidation and reduction may be continued, provided the metal had been made thoroughly red-hot to begin with. The hydrogen should be pure, and free from traces even, of sulphur or arsenic, in order that the experiment be successful.

Reduction of Isatine to Indigo-Blue.-The Chemical News, in its admirable summary of the results of research abroad, gives the following note by Herren A. Bayer and A. Emmerling. They state that when isatine, previously pulverised, is mixed with fifty times its weight of a mixture of equal parts of terchloride of phosphorus and chloride of acetyl, to which some phosphorus is added, and this mixture is heated for several hours to from 75° to 80° in a sealed tube, and the bright green coloured liquid contained in the tube poured into a large bulk of water, next filtered, and then left standing for twenty-four hours in a large basin, a dark blue pulverulent substance is gradually deposited, which, being collected on a filter and washed with alcohol, yields a body in all its properties fully identical with indigo-blue. The quantity so obtained varies from 10 to 20 per cent. of the weight of the isatine employed. The authors enter at great length into collateral matters of interest as regards the synthesis of indigo-blue; but unless we were to produce a series of complicate formulæ, we could not give any useful abstract of that portion of their paper.

Researches on Alizarine.—A paper on this subject, which is now becoming popular enough among chemists, appears from V. Wartha in the Berichte der Deutschen Chemischen Gesellschaft zu Berlin, No. 12. The author states that, being engaged with researches on Turkey-red dyeing, he has found that the peculiarly brilliant red colour known by this term is due to a peculiar combination of alizarine with a fatty acid, which compound is soluble in a mixture of ligroine and ether, and does not even adhere very strongly to the cloth, since it may be readily removed therefrom by the liquid mixture alluded to. On evaporating this solution, there is left a brilliantly scarletcoloured fatty substance, which, only after having been fused with caustic potassa, exhibits the characteristic reactions of alizarine. The author also states that the preparation of alizarine from madder is readily performed by first exhausting the substance (madder) with ligroine (light petroleum oil), and next treating it with a mixture of alcohol and hydrochloric acid (alcohol

saturated with the gas). On diluting this solution with much water, the alizarine is precipitated, in almost a chemically pure state, in the shape of an orange-coloured flocculent body. A carefully-conducted comparative investigation has proved to the author that the vegetable alizarine sublimes at between 130° and 140°. The synthetically-prepared artificial alizarine requires a temperature of from 280° to 300°.

The Formation of Ozone during Combustion.-In a recent number of the Chemical News it was stated by Mr. Loew that in a peculiar experiment ozone was formed. In reference to this Herr J. D. Boeke has recently been performing some experiments of interest. In Herr Boeke's experiment a stream of oxygen instead of air was blown through the luminous flame of a Bunsen's burner into the mouth of a glass balloon, and he really found that the air in the balloon had assumed a peculiar odour, and the property of colouring blue a mixture of starch paste and kalium iodide. Both changes are the result of the formation of a compound of oxygen and nitrogen (probably dinitric trioxide or nitric dioxide), not from the formation of ozone, as Mr. Loew asserts. The gas in the balloon being shaken with a little water, this was unable to colour the kalium iodide starch; kalium hydroxide, however, shaken with the gas, caused a dark blue coloration in the mixture, after having been acidified with dilute sulphuric acid. It is almost unnecessary to add that he had first assured himself by a blank experiment that the iodide was sufficiently free from iodate not to cause errors. With ferrous sulphate and strong sulphuric acid it gave the characteristic reaction of nitrates and nitrites. So when Mr. Loew declares that he was able to "identify the formation of ozone by its intense odour and the common tests," he was a little rash in this conclusion.

The Carbonates of Ammonia.-In a long and valuable memoir on the combinations of carbonic anhydride with ammonia and water, Dr. Divers has greatly extended our knowledge of these oft-examined yet imperfectlydescribed carbonates. From this memoir it appears that there are three, if not four, ammonium-carbonates which crystallise from their solutions, and that these have a simple, serial relation to each other. They are the hyperacid carbonate (?), the acid or bicarbonate, the half-acid carbonate discovered by Rose, which the author shows has a formula different from that hitherto ascribed to it, and the normal carbonate, which the author considers Dalton obtained, but which will owe its recognition henceforward by chemists to the labours of Dr. Divers. By digestion at a gentle heat with strong solution of ammonia the carbonates of ammonium are converted into carbamate of ammonium, thus furnishing a very instructive instance of the dehydration of the ammonium salt of one of the simplest acids, and this, too, in the presence of water. The carbonate of ammonia, in commerce, is very uniform in composition nowadays, and this differs from the composition hitherto given to it. Instead of being (CO2),(OH)2(NH3), it is (CO2),OH,(NH3)3. When sal-ammoniac and chalk are heated together the reaction is not such as it is represented to be, and the product is not the carbonate of commerce. This is a result of the refining process; the products of the first distillation being ammonium-carbamate and water. These are some of the facts contained in this memoir; for others, and a mass of minor details, the reader should refer to the memoir itself in the June, July, and August numbers of the Journal of the Chemical Society.