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contraction is quite unconnected with the absorption of oxygen, which occurs when humus is shaken with air and an alkali. The amount of the contraction is proportional to the quantity of alkali and the time of shaking. The addition of borax prevents it entirely.

A solution prepared as follows, whilst not containing sufficient free alkali to produce this contraction, decomposes ammonia readily. To an excess of calcium hydroxide 200 c.c. of water and 15 c.c. of bromine are added; the mixture is allowed to remain for several days that the solution may become saturated with lime; it is then filtered and mixed with a saturated solution of borax before use. If it is desired to render this solution more strongly alkaline, it is necessary to ascertain first the maximum amount of alkali which can be used without causing contraction. This may be done by shaking the earth with borax solution, and gradually increasing quantities of sodium hydroxide in a flask, closed with a cork, carrying a sealed capillary tube, the point of which is afterwards broken while in connection with the azotometer. The flask should have a thermometer inserted through a tubulus, and proper precautions against change of temperature must be taken. M. J. S.

Griess' Reaction for Nitrous Acid in Presence of Hydrogen Peroxide. By C. WURSTER (Ber., 19, 3206–3208.)-Fresh saliva failed to give Griess' colour reaction for nitrites, but coloured tetramethylparaphenylenediamine paper. This is accounted for by the presence of hydrogen peroxide which would oxidise the nitrite to nitrate, so that the coloration could only take place in presence of an excess of nitrite. The absence of nitric acid in fresh saliva is seen when saliva is added to two portions of metaphenylenediamine sulphate in glacial acetic acid, one of which is previously treated with a drop or two of ammonia; no coloration is produced in the solution free from ammonia, whilst that containing ammonia is soon more or less coloured, owing to the oxidation of the ammonia to nitrous acid by the hydrogen peroxide.

Saliva obtained from a large dog was found to contain much hydrogen peroxide, and to be free from nitrites and potassium thiocyanate. N. H. M.

Apparatus for Kjeldahl's Method of Nitrogen Determination. By H. P. ARMSBY and F. G. SHORT (Amer. Chem. J., 8, 323-326). The distillation flask is closed by a rubber stopper with three holes. Through one hole passes a tube of half inch diameter, widening upwards to 1 inch, and about 4 inches long; sealed into the side of this is the exit tube, which is connected with a block-tin condenser; the top of the 1-inch wide tube is closed by a rubber stopper, through which passes a stoppered funnel whose stem reaches to the bottom of the flask, the remaining space in the wide tube is filled with glass beads, to stop any spray. The second hole serves for a small mercury valve to admit air in case of sudden absorption or cooling. The third hole carries a syphon tube reaching to the bottom of the flask, this serves to empty and clean the flask after each operation, so that the apparatus is never dismounted. H. B.

Determination of Phosphorus in Iron and Steel. By P. VORWERK (Zeit. anal. Chem., 26, 51).-The modified method proposed by Huss (Abstr., 1886, 1073) yields results which are too low; the organic matters dissolved by the nitric acid render the precipitation of the phosphoric acid incomplete, a defect which is not removed by the quarter-hour's boiling, or by the addition of ammonium chloride. M. J. S.

Determination of Boric Acid. By T. ROSENBLADT (Zeit. anal. Chem., 26, 18-23).-Boric acid can be completely volatilised by repeated distillation with dry methyl alcohol. The substance is placed in a dry flask fitted with a stopcock funnel and condenser. The lower end of the condenser is fitted by a cork into an empty flask, from which a double bent tube dips under ammonium carbonate solution. The substance is moistened with methyl alcohol, then a small excess of concentrated sulphuric acid is added, and a further quantity of methyl alcohol. This is distilled over into the lower flask, as are also several subsequently added quantities: 40 to 50 c.c. of the alcohol in 8 or 10 portions will carry over 0.3 gram of B2O, completely. The distillate is then mixed with ammonium carbonate and evaporated in a platinum basin, in which about 3 parts of magnesia for 1 of boric acid have been strongly ignited and weighed. The increase of weight gives the amount of B2O,.

Substances insoluble in acid require to be fused with alkaline carbonates. If containing fluorine, they must first be strongly ignited. If chlorides are present, an excess of silver sulphate must be added before distilling. The methyl alcohol employed must not darken or evolve sulphurous acid when heated with sulphuric acid.

The test determinations communicated are highly satisfactory. (Compare next Abstract.) M. J. S.

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Separation and Estimation of Boric Acid. By F. A. GOOCH (Chem. News, 55, 7-10; compare preceding Abstract).-Boric acid is proved experimentally to be more volatile in methyl alcohol than in ethyl alcohol or in water. This volatility is diminished by the presence of water, hydrochloric acid, amyl alcohol or sulphuric acid; but the residue from the treatment of borax with hydrochloric, nitric, or acetic acid parts readily with its boric acid in the vapour of methyl alcohol; in the last case owing to the tendency of sodium acetate_to become alkaline, the residue must be kept acid with acetic acid. the retention of the boric acid thus volatilised, so as to weigh it after an ignition, magnesium oxide proved unsuitable, owing to its insolubility; lime, on the other hand, is quite efficient, but with lime, hydrochloric acid must not be used for decomposing the borate, as the chlorine of calcium chloride is not readily driven off by heat. On these facts the following method is based:-The substance dissolved in water and nitric acid, or acetic acid, or in the acids alone, is run into a retort connected with a condenser and receiver, and heated by means of a paraffin bath and distilled to dryness. The residue is treated six times successively with 10 c.c. of methyl alcohol, being evaporated to dryness after each addition; when nitric acid is used, a little water is added from time to time to break up the cake of

nitrate; when acetic acid has been used, a few drops of acetic acid are added with the fourth portion of methyl alcohol. In all cases the receiver contains a quantity of lime ignited and weighed before and after the distillation; any increase in the latter weighing is due to boric acid. When chlorides are present in the original substance it is best to dissolve it in nitric acid, and remove the chlorine by means of silver nitrate before distilling, although decomposition with acetic acid and direct distillation may be used successfully. The number of distillations required really depends on the quantity of boric acid present. A neat and convenient apparatus is described which may prove useful in other similar operations, besides this for which it was devised. Many experimental details of interest are also included in the original paper.

D. A. L. Absorption Tubes for Estimating the Carbonic Anhydride in Air. By T. C. VAN NUYS (Amer. Chem. J., 8, 315–323; compare Abstr., 1886, 835).-The carbonic anhydride is absorbed in two long tubes shaped like Guy-Lussac burettes, but provided at the bottom with an outlet and stopcock. They are filled with air free from carbonic anhydride, baryta-water is introduced, and the air to he analysed aspirated through; the tubes are then emptied and rinsed into a flask for titration. Full particulars are given of all the precautions necessary. H. B.

Microscopical Analysis. By K. HAUSHOFER (Jahrb. f. Min., 1887, 1, Ref., 13—15).—A number of substances, when treated with hot, concentrated sulphuric acid in an assay tube (0·2 c.c. of acid to 10 mgrms. of the substance), are oxidised and partially dissolved. On cooling, anhydrous sulphates frequently separate out, the crystalline form of which, detected under the microscope, may be characteristic for certain metals. Thus, copper compounds give a green residue, which, under the microscope, is seen to consist of colourless or pale violet hexagonal plates (rhombic ?), the plane angles of which measure 120°. Iron compounds give colourless, thin tablets, rhombic in appearance, with an acute plane angle of 87°. Zinc compounds give prisms with forked ends, suggesting the forms of gypsum crystals. Mercury compounds give a colourless crystalline powder; the crystals rarely have distinct forms; they are tabular crystals with a rhombic character. Silver compounds, with the exception of the halogen salts, give rhombic pyramids with an acute basal angle of 77°, and with indications of the planes of a doma, and of vertical pinacoids. Only a few of the nickel compounds occurring in nature give salts which crystallise distinctly. Nickel arsenide, gersdorffite, and ullmannite give forms resembling square prisms with a pyramid superimposed. Of the manganese compounds, manganese spar and manganese sulphide give rather large prisms with oblique terminal planes. On exposure to the air, a mass of smaller prisms is formed. Manganite, braunite and hausmannite give colourless prismatic crystals. Arsenic compounds give octahedra of As2O3, in addition to the sulphates. Antimony oxide and sulphide give colourless, prismatic crystals. All the borates occurring in nature are decomposed in concentrated sulphuric acid. On cooling, the boric acid separates out in

what seem to be hexagonal tablets. This method is not adapted for the detection of boron in tourmaline and axinite. B. H. B.

Microchemical Tests. By K. HAUSHOFER (Jahrb. f. Min., 1887, 1, Ref., 15—17).—Tellurium treated with concentrated sulphuric acid gives an amaranth-red colour. On heating, the red colour disappears, and tellurous anhydride separates out on cooling in colourless, hexagonal tablets. The crystals are soluble in water, and on evaporation separate out again; the tellurous anhydride obtained by evaporation being rhombic.

Selenium dissolves in concentrated sulphuric acid with a leek-green colour, and on cooling gives a brick-red sediment of selenium.

Bismuth treated with boiling, concentrated sulphuric acid gives numerous very small prisms on cooling. On exposure to air, these rapidly dissolve, and acicular crystals grouped in the shape of a star are formed. These also disappear after a short time. After a few hours large, transparent, monoclinic tablets are formed.

Solutions containing 0.1 gram of barium chloride in 20 to 80 c.c., treated with 1 c.c. of concentrated hydrochloric acid, give, with dilute sulphuric acid, rectangular crystals which may be distinctly recognised. With strontium, very perfect, rhombic crystals are obtained.

On precipitating lead from boiling dilute solutions with sulphuric acid, the sulphate appears as sharply defined rhombic tablets. If this precipitate is washed and treated with a drop of hydrochloric acid, the characteristic long lamellæ and rhombic crystals of lead chloride are immediately formed. B. H. B.

Titration of Zinc and Cadmium Sulphides with Iodine. By P. v. BERG (Zeit. anal. Chem., 26, 23-25).-The filter containing the washed sulphides is thrown, as soon as it is drained, into a bottle which contains about 800 c.c. of recently boiled water, and from which the air has been expelled by carbonic anhydride. The bottle is well shaken to break up the precipitate, otherwise the separated sulphur would partially protect the metallic sulphide. A moderate quantity of hydrochloric acid is added (which need not entirely dissolve the precipitate), and then an excess of iodine solution of known strength. The residual free iodine must, without loss of time, be titrated with thiosulphate. The whole operation takes about five minutes. The results obtained on known quantities ranged from 988 to 100.2 per cent. In the case of manganese, only about 95 per cent. was obtained. Cobalt and nickel sulphides are not attacked by the acid iodine solution. M. J. S.

Valuation of Zinc-dust. By F. WEIL (Compt. rend., 103, 1013 -1014). The zinc-dust is mixed with a standard solution of cupric chloride containing 10 grams of metallic copper per litre, and when all the zinc has been dissolved, the liquid is poured off, strongly acidified with hydrochloric acid, and the excess of copper determined by means of a standard solution of stannous chloride (Abstr., 1883, 509).

The copper solution is prepared by dissolving cupric oxide (from

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the nitrate) in hydrochloric acid, and then adding ammonia until a very slight turbidity is produced. If the substances are mixed in a platinum dish, solution takes place rapidly. If a porcelain dish is used, a flat spiral of platinum wire must be placed in the liquid. In order to ascertain if all the zinc has been dissolved, the precipitate is touched with a clean platinum wire; if the wire acquires a red or black coating some zinc is still undissolved, but if it remains bright the reaction is complete. C. H. B.

Detection of Mercury in Organic Liquids. By A. ALMÉN (Arch. Pharm. [3], 24, 1031).-This method is a modification of Reinsch's. In the liquid mixed with 8-10 per cent. hydrochloric acid a well-ignited copper or better brass wire is immersed, and the whole is heated gently during 14 hours. The wire is then white if much mercury is present or dirty grey if less; it is dried on paper, placed in a small glass tube, which is sealed off a few mm. above the wire. On carefully heating so as to distil off the mercury, there appears close to the wire a reddish-brown non-volatile incrustation, then mercury beads, beyond yellow oil drops, and finally a little water. lens or microscope may be necessary for the examination of the deposits. In the case of urine, a considerable quantity can be heated with aqueous soda, with or without sugar as a reducing agent; after settling, the test can be applied to a portion of the sediment.

J. T. Separation of Mercury and Palladium from one another, and from Lead, Copper, and Bismuth. By T. ROSENBLADT (Zeit. anal. Chem., 26, 15-18).-The sulphides of mercury and palladium are soluble in potassium thiocarbonate, whilst those of lead, copper, and bismuth are insoluble. A solution prepared by dissolving 1 part of sulphur in 2 parts of carbon bisulphide and adding 23 parts of aqueous potash of sp. gr. 1·13, will dissolve 20 grams of mercuric sulphide per litre.

The mixed sulphides are boiled for half an hour with a sufficient quantity of the thiocarbonate, and the insoluble sulphides are washed until the filtrate is colourless. From the solution, both mercury and palladium may be thrown down by hydrochloric acid, but a stream of carbonic anhydride precipitates the mercury only. The mercuric sulphide contains free sulphur, which, after drying, may be con"veniently removed by extraction with carbon bisulphide in a Soxhlet's apparatus.

The results reported leave nothing to be desired as regards accuracy.

M. J. S.

Estimation of Alumina and Iron Oxide in Mineral Phosphates and Manures. By R. T. THOMSON (J. Soc. Chem. Ind., 5, 152-154). After considering the methods of separating the phosphates of aluminium and iron from acid solutions containing these substances in conjunction with calcium phosphate, the author gives a process for determining these compounds in commercial phosphates. Two or three grams of the substance is dissolved in hydrochloric acid, evaporated to dryness, the residue redissolved in hydrochloric acid, diluted, and filtered. The phosphates are then precipitated

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