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-The experiments were made on a sandy soil, with barley and oats. 200 kilos. of Chili saltpetre and 300 kilos. of ammonium sulphate were used to the hectare; the plots manured with the former salt showed a better result in grain, but a smaller yield of straw. Compared with unmanured plots, the increase obtained by manuring was—

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Calculating the cost of the manures and the market prices of barley, oats, and straw, the author considers the Chili saltpetre the more paying of the two.

J. F.

Experiments with Chili Saltpetre. By v. MAGERSTEIN (Bied. Centr., 1886, 581-583).—In order to compare the effects of this manure when used as top-dressing and when dug in, the author prepared plots of 7 to 8 square metres all cultivated in the same way, except as regards the application of the manure. In the cases of potatoes and oats, the top-dressing gave the better results, but the contrary was the case with barley; the difference is attributed to the dryness of the season. The solution of the salt was slow and concentrated; therefore unfavourable to growth. The roots of barley came first in contact with it, whilst the deeper roots of potatoes and oats received a more dilute solution and were stronger when it reached them. J. F.

Analytical Chemistry.

Kjeldahl's Method of Estimating Nitrogen. By C. ARNOLD (Arch. Pharm. [3], 24, 785-794).-The author shows that this method (Abstr., 1884, 364; 1885, 930) is also applicable to nitrates, nitro- and cyanogen-compounds, in the presence of benzoic acid, sugar, mercury, and copper sulphate; further, in the case of alkaloids and other compounds that can be treated by this method, oxidation by potassium permanganate is unnecessary if the boiling be continued until the warm liquid acquires a bluish-green tint, becoming colourless on cooling; this takes place tolerably quickly in the presence of mercury and copper. That the oxidation has been completed can readily be ascertained by adding a crystal of potassium permanganate, which should give a persistent violet or green coloration. A description of the apparatus used by the author is given.

J. T.

Separation of Arsenic and Antimony. By ZAMBELLI and LUZZATO (Arch. Pharm. [3], 24, 772).-These elements can be separated, even in forensic cases, by treating the still moist sulphides with hydrogen peroxide at 40° for some hours, then heating to near 100°

and filtering. The arsenic acid formed goes into the filtrate, whilst the insoluble antimony oxide remains on the filter. The method is said to be very delicate.

J. T.

Detection of Thiosulphate in Hydrogen Sodium Carbonate. By BRENSTEIN and T. SALZER (Arch. Pharm. [3], 24, 761).— According to Brenstein, the reaction given for thiosulphate by Mylius. is not characteristic, as other oxygen-compounds of sulphur, such as sulphites, give rise to the formation of hydrogen sulphide. A better test for thiosulphate is to add to a 5 per cent. solution of hydrogen sodium carbonate a few drops of silver nitrate solution, then excess of nitric acid, and heat to boiling; even minute traces of thiosulphate give an immediate dark precipitate of silver sulphide.

According to Salzer, the absence of thiosulphate is easily ascertained by adding a few drops of iodine solution to about 20 c.c. of a saturated solution of hydrogen sodium carbonate; the solution must have a yellowish tint. Decolorisation of the iodine solution does not necessarily imply the presence of thiosulphate, since normal carbonate, the most commonly occurring impurity, produces this effect. Both authors found thiosulphate to be a constant impurity of ordinary qualities of hydrogen sodium carbonate, whilst the better qualities were mostly free from it.

J. T.

Estimation of Small Quantities of Silver in Burnt Pyrites. By E. THILO (Chem. Zeit., 10, 822; 1065-1067).-The amount of silver in burnt pyrites is ordinarily 0·003-0008 per cent., and to obtain trustworthy results material containing 001 gram of silver should be taken for analysis, or about 300 to 500 grams of pyrites. Many difficulties have been encountered in endeavouring to deal with these large quantities of material so as to get all the silver. Experiments show that the decomposition of the whole mass is out of the question, therefore methods for extracting the silver, &c., were tried; treatment with nitric acid or with gaseous chlorine, and subsequent extraction of the silver chloride proved unsuitable. Digestion with chlorine-water was somewhat better; but bromine or bromine-water gives the best results. The powdered burnt pyrites is passed through a 0-25-mm. mesh sieve, and about 300-500 grams of it is placed in an acid-proof iron basin; it is well covered with water, and while vigorously stirred, bromine is added until present in excess. After 24 hours it is heated on a water-bath for one hour with frequent stirring, treated with excess of ammonia, then with 500 grams of ammonium chloride, and 1 litre of water. The mass is boiled for an hour, and filtered. The residue is dried, ignited at a low red heat, and again treated with ammoniacal ammonium chloride, by which means all the silver is extracted. Inasmuch as copper is quite as difficult as silver to extract by means of bromine, and as the amount of copper in the pyrites is reduced from 5 per cent. to a trace (0.01 per cent.) by the above treatment, this may be used as an indicator of the progress of the desilvering, and in practice when the copper is reduced to this amount it may be safely inferred that all the silver is removed. The solution, about 4 litres, is made acid with hydrochloric acid; it is not

affected by daylight either before or after acidifying. The silver, copper, and lead are then precipitated by means of chemically pure zinc. When the precipitation is complete, the solution is colourless (or rose-red if cobalt is present), and is not turned blue by ammonia. As the precipitate contains, most likely, silver chloride and bromide, and some iron oxide, it is fused with potassium cyanide, and subsequently with anhydrous borax, the temperature being raised to melt the copper. The regulus is dissolved in nitric acid, and the silver either precipitated by means of hydrochloric acid or determined electrolytically. Silver determinations may also be made in ordinary pyrites, which is first roasted carefully, and then treated in the above manner. Good results have been obtained by this method, with roasted copper schist, with spathic iron ore containing argentiferous tetrahedrite and pyrites, and with other ores. A determination can be completed in three days. D. A. L.

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Comparative Gasometric Assaying with Especial Reference to the Valuation of Zinc Powder and the Testing of Carbonates. By J. BARNES (J. Soc. Chem. Ind., 5, 145–147).--In a previous communication (Trans., 1881, 462), the author described a method for the valuation of zinc powder, consisting in measuring the amount of hydrogen liberated on treatment with an acid. author has since devised a method and constructed an apparatus for gasometric assaying, contrived originally for the valuation of zinc powder, but applicable also to the estimation of other substances, which may be made to canse or control the evolution of gases. method, which is described in detail in the paper, is a comparative one, and requires at least two graduated instruments, each provided with a suitable gas evolving arrangement. A substance of known value, taken as the standard, is placed in one, and the sample to be examined in the other instrument. The value of the sample is บ W then calculated by the following formula: Ra; where V V 20

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equals the volume of gas from standard, v the volume of gas from sample, W the weight of standard, and w the weight of sample. R is the amount of pure substance or its equivalent in unit of standard, and the amount of pure substance in unit of sample.

D. B.

Determination and Valuation of Copper in Ores and Products for Commercial Purposes, with some Remarks on the Assay of Gold in Bar Copper. By J. W. WESTMORELAND (J. Soc. Chem. Ind., 5, 48-64).-Estimation of Moisture.-This, although apparently a simple process, is conducted very differently by various assayers, and the author proposes that the temperature and manner in which the moisture is to be taken should be more clearly defined than it is at the present time.

Wet Assay of Copper.-Having examined a large number of samples of all kinds of copper ores and products by several wet processes, the author has given the iodide process as modified by Brown the preference being more trustworthy and accurate than the electrolytic process. For cupreous pyrites, burnt ores, &c., the following method

may be used. From 50 to 150 grains of the sample is dissolved in acids, evaporated to dryness with excess of sulphuric acid, diluted with water and filtered. From this solution, the copper is separated with sodium thiosulphate, the precipitate dried, ignited, dissolved in nitric acid, evaporated with sulphuric acid to separate traces of lead, diluted with water and filtered, sodium carbonate added in excess, and then acetic acid to acid reaction. The solution is then titrated with potassium iodide. As an alternative method, the ore may be calcined, dissolved in hydrochloric acid, the ferric salt reduced by boiling with a solution of sodium sulphite, and hydrogen sulphide passed through the cold solution; the precipitated sulphides are then washed, and the process conducted as before. Richer copper ores, mattes, precipitates, &c., are dissolved in acids, and the solution precipitated either with sodium thiosulphate or hydrogen sulphide, the sulphides being dissolved in acids, and treated as before. The accuracy of this process was tested by numerous experiments, in which known weights of pure electrotype copper, silver, arsenic, antimony, lead, cadmium, bismuth, tin, manganese, zinc, and iron salts were used. The solutions were made to represent cupreous burnt ores, mattes, cupriferous lead regulas, second quality and rich precipitates, &c. Experiments were also made in many cases with the metals separately. The electrodeposition method may be employed in cases where it is desirable to have results of two separate and distinct processes, it being noted that with pure solutions of copper, accurate results are obtained, whilst when silver or bismuth are present they are precipitated, and in one experiment tin was also deposited with the copper. In the presence of ferric salts, the deposition is retarded. It was found that whilst the results with refined or bar coppers and rich precipitates agree with those obtained by the iodide process, those obtained by electrolysing sulphuric acid solutions of mattes, copper ores, &c., are generally slightly below the true percentage. With burnt ores, cupreous pyrites, and ores containing but little copper, the author first precipitates with hydrogen sulphide, dissolving the sulphide in nitric acid, and evaporating this solution with excess of sulphuric acid, the sulphates dissolved in water give a solution from which copper (and bismuth) is readily deposited. The results by the battery process are generally from 0·01 to 0.04 per cent. higher than by the iodide process, this being cansed by a slight deposit of bismuth.

The Cornish Process of Dry Assay. This process is considered to be inaccurate and misleading, and is also liable to serious variation even in the hands of experienced operators.

The author is of opinion that in cases where the sulphur contents of pyrites are sold to alkali works, the burnt ores being returned to the vendors, an accurate wet assay forms the best check on the copper contents of the ore delivered to and received from the alkali works.

In the remaining part of the paper, the methods in vogue for fixing the prices payable for copper in pyrites, copper ores, &c., are discussed. Reference is also made to the assay of gold in bar copper, and the opinion is expressed that these assays are not conducted as carefully as they should be, taking the value of the metal into consideration. D. B.

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Estimation of Ammoniacal Nitrogen in Soils, and the Amount of Assimilable Nitrogen in Uncultivated Land. By A. BAUMANN (Landw. Versuchs-Stat., 1886, 247-303).-The methods employed to estimate the ammonia in soils are unsatisfactory. Schlösing's method, whereby the ammonia is freed by means of milk of lime or sodium hydroxide, gives results too high, probably owing to the formation of ammonia from other compounds during the period (2-3 days) required for the process. In Boussingault's process as modified by Schlösing, a hydrochloric acid extract of the soil is treated with magnesia usta, but the ammonia collected in acid must not be estimated by titration, but must be azotometrically determined; nor must cork nor caoutchouc be employed in the formation of the apparatus. The liquid in the evolution flask must be boiled for at least an hour, and the magnesia usta must be fresh. With these two processes, it is found that humous soils, when treated with sodium hydroxide, continuously yield ammonia; if the soil, after treatment with magnesia, be further treated with sodium hydroxide, another supply of ammonia is obtained, but only in the case of soils rich in numus. Knop's process, in which the ammonia is decomposed by brominated sodium hydroxide solution, is vitiated by the fact, noticed by Knop and others, that in the presence of the soil itself a contraction of the volume of gas enclosed in the apparatus occurs; this contraction was stated by some to be due to absorption by the organic matter, whilst others considered the oxides of iron in the clay to be the real cause; also it had been stated that the presence of borax prevented this contraction. To ascertain the cause of the contraction, a sample of stiff soil poor in humus, was taken from uncultivated land at a depth of 15-20 cm.; this sample seemed free from humus, although root-fibres were visible; at a distance of 40 m. from this spot another sample was drawn from a depth of 2-10 cm., this was close to a pine 50 years old. The sample showed humus, and when dry was grey. At another spot, close to a 100 year old pine, a third sample was taken, and this when dry was dark-brown. These last two samples overlaid a soil similar to the first sample. Employing these samples, the author argued that if the contraction was due to the clay and the iron, and not to the humus, then identical contractions would be observed when equal quantities of all samples were subjected to like conditions. On the other hand, if the phenomenon is caused by the humus, then that sample richest in humus would produce the greatest effect on the volume of the gas, and when box was employed no contraction should occur. It appears that the ferruginous soil poor in humus produced no contraction, but rather an increase of volume after the first hour; this is explained by the probable presence of nitrogenous matter decomposable by the brominated alkali. The presence of borax assisted the evolution of gas.

Experimenting with humous samples, it was found that the volume of gas evolved by Knop's method stands in no ratio to the percentage of ammonia present; this remarkable result was most manifest in the case of the third sample, which contained most humus, for then the contraction was evident when only 5 grams were used,

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