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Burette Jet. By W. LEYBOLD (Zeit. anal. Chem., 26, 230).-This jet, which requires no pinchcock, is closed at its upper end. A hole is blown in the side near that end, and the rough glass is filed away. The jet is thrust into the rubber tube so far that the hole is covered. The liquid is then delivered by squeezing up the rubber where it covers the hole. M. J. S.

Use of "Solid Bromine" for Decomposing Sulphuretted Minerals and Metallurgical Products. By A. BRAND (Zeit. anal. Chem., 26, 222-226). The article introduced into commerce by Franke as 66 Bromum solidificatum" consists of siliceous earth fritted together by means of a trace of alkali in the form of rods, and saturated with bromine. The rods of 7 mm. diameter contain about 1 gram; those of 15 mm. about 3 grams per centimetre. They afford a convenient and economical means of employing a definite quantity of bromine for any operation, especially as a substitute for chlorine in the attack of mineral sulphides, &c. The boat containing the substance is thrust into a tube connected with the bulbs for absorbing the volatile bromides; a sufficient number of the bromine rods are then inserted, and the tube is closed by a plug of plaster of Paris and a cork. The bromine is then driven over the heated substance by warming the rods. Sulphur, antimony, arsenic, and mercury are completely volatilised; copper, lead, nickel, cobalt, and silver remain in the boat; iron and zinc are incompletely driven over. A gram of substance can be completely decomposed in half an hour.

M. J. S.

Iodometric Studies. By G. TOPF (Zeit. anal. Chem., 26, 137217). The addition of ammonium carbonate to solution of thiosulphate, recommended by Mohr as a means of preserving its strength, has no such effect, and moreover leads to serious errors in titrating iodine in a solution which is not acidified. Although ammonium carbonate has little effect on iodide of starch, yet with iodine it forms both iodate and hypoiodite, the latter of which immediately oxidises some of the thiosulphate to sulphate instead of to tetrathionate. The consequence is that less thiosulphate is required for decoloration, and although the addition of hydrochloric acid, after the disappearance of all the iodine, sets free that which had been converted into iodate, the results are still deficient by the amount consumed in forming sulphate. A series of titrations was made with thiosulphate solutions to which ammonium carbonates of various composition were added in the proportion of 2 and 5 grams per litre respectively. The deficiency in the quantity of iodine indicated was observed in every case, except in that in which, after the addition of the carbonate (2 grams per litre), carbonic anhydride was passed through the solution to produce ammonium hydrogen carbonate. The deficiency ranged from 3 to 20 per cent.; it increased with increase in the quantity of ammonium salt added, but diminished as that was more highly carbonated.

If an alkaline carbonate is present in a liquid, a little more iodine must be added to produce the blue colour with starch than would be the case in the absence of the alkali. On adding hydrochloric acid, all the missing iodine is recovered. The normal carbonates of the fixed

alkalis have a greater effect than that of normal ammonium carbonate, whilst the hydrogen carbonates of all the alkalis are practically without influence. Nevertheless even these, and other substances of very feeble alkalinity added to an iodine solution before titrating with thiosulphate, have an effect similar to that of ammonium carbonate on the thiosulphate solution, and to an extent far exceeding their retarding action on the formation of iodide of starch. With the hydroxides of sodium, barium, and calcium, the tendency is chiefly to the formation of iodate; nevertheless, as much as 34 per cent. of the iodine present has been observed to be consumed in the formation of sulphate. Dilution, or reduction of the proportion of alkali added, diminishes the total quantity of iodine absorbed, but increases the oxidation relatively to the formation of iodate. With the normal carbonates of sodium, potassium, and lithium, oxidation takes place to about the same extent as with the hydroxides, but there is less iodate formed. The hydrogen carbonates have a lower, but by no means insignificant action. It is entirely one of oxidation, no iodate being formed. With ammonia and normal ammonium carbonate, the tendency is chiefly to the formation of sulphate; the proportion of iodate rises with increased proportion of carbonic acid. The effect of ammonium hydrogen carbonate is far greater than that of the corresponding sodium and potassium salts.

Mixtures of alkaline carbonates with excess of barium, calcium, or zinc chloride, although neutral to phenolphthaleïn, still cause considerable oxidation to sulphate. Little or no iodate is formed. Zinc and magnesium hydroxides and magnesium carbonate cause both oxidation and formation of iodate. Aluminium hydroxide, on the contrary, has no action. An excess of alum added to ammonia produces a mixture which is entirely without influence on the titration of iodine. M. J. S.

Reaction of Thiosulphates. By F. A. FLÜCKIGER (Chem. Centr., 1887, 362; compare this vol., p. 297).-The reduction of thiosulphates to sulphides by sodium, or by a mixture of zinc and iron filings in presence of soda, or by simple ignition, had been already published by the author in his “ Pharmaceutical Chemistry."

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M. J. S.

Zinc Determination. By M. BRAGARD (Chem. Centr., 1887, 365). -Of the methods of precipitation as zinc sulphide, that with an alkaline sulphide, when Fresenius' precautions are attended to, gives the sharpest results, but the precipitate is troublesome to filter. Finkener's modification, in which the zinc is precipitated by hydrogen sulphide from a liquid very feebly acidified with sulphuric acid and largely diluted, yields a pulverulent precipitate which is easily washed. Precipitation from a formic or acetic acid solution gives good results, and is suitable for the separation of zinc from iron and nickel.

In the volumetric determination by sodium sulphide, ferric hydroxide may be used as an indicator. If test-papers are used those of lead and thallium exceed all others in sensitiveness. In determining volumetrically by potassium ferrocyanide with uranic nitrate as indi

VOL. LII.

2 z

cator, a piece of filter-paper must be laid over the uranium paper so that only the clear liquid comes in contact with the latter.

M. J. S. Detection and Estimation of Aluminium in Wine and Grapes. By L. L'HOTE (Compt. rend., 104, 853-855).-250 c.c. of wine is evaporated to a syrup in a platinum dish, and mixed with pure sulphuric acid. The carbonised mass thus obtained burns readily to a white ash in a muffle. The ash is treated with 15 c.c. of nitric acid, mixed with 100 c.c. of a solution of ammonium molybdate in nitric acid (50 grams molybdic acid per litre), heated to boiling, the phosphomolybdic acid filtered off, and the iron and aluminium precipitated in the filtrate by ammonia and ammonium sulphide. The precipitate is roasted in presence of air, reduced in a current of hydrogen, and then heated in a current of hydrogen chloride, when the iron volatilises. The residue is treated with hydrofluoric and sulphuric acids to remove silica, strongly heated and weighed. It may be proved to be aluminium by heating it on charcoal with cobalt nitrate. A blank experiment is made with the same reagents and the aluminium found is deducted in each experiment.

Wines from seven localities were found to contain 0.012-0.036 gram of alumina per litre.

479 grams of red grapes gave 0·013 gram of alumina, whilst the stalks from which they had been stripped (6.482 grams) contained 0.003 gram. C. H. B.

Detection and Estimation of Vanadium in Minerals. By L. L'HOTE (Compt. rend., 104, 990-992).-The substance (4 parts) is intimately mixed with carbon (1 part) and heated at 250° in a current of chlorine in a tube connected with a condensing apparatus consisting of several bulbs containing distilled water. If the substance contains arsenic, it should first be roasted in presence of air. The presence of vanadium is indicated by the formation of a red coloration, due to vanadic acid in the first bulb. If the quantity is too small to be recognised in this way, the contents of the bulbs are dissolved in dilute hydrochloric acid, evaporated to dryness, and moistened with colourless ammonium sulphide, when the characteristic colour of vanadium sulphide becomes visible.

Small quantities of vanadic acid can be estimated by Margueritte's method for the estimation of small quantities of iron. A standard solution of vanadium is prepared by dissolving vanadic anhydride in sulphuric acid; 1 cc. of this solution = 0.00028 gram of vanadium. The solutions can be reduced with zinc and titrated with very dilute permanganate solution, care being taken to use distilled water which has no action on the permanganate.

If the proportion of vanadium in the mineral is considerable, the contents of the first bulb will be greenish-blue, and when evaporated with ammonia and heated to redness vanadic anhydride is left, and can be weighed.

By this method, the author has detected vanadium in two specimens of bauxite, two specimens of pitchblende, a hydrated ferric oxide, and basic Bessemer slag. C. H. B.

Estimation of Vanadic Acid. By A. DITTE (Compt. rend., 104, 982-987).-When ammonium vanadate is precipitated in presence of ammonium chloride and washed with a solution of this salt as in Berzelius' method, it is necessary to remove the ammonium chloride adhering to the precipitate, since it would partially reduce the latter on beating. If strong alcohol is used for this purpose, the ammonium chloride is precipitated in the filter, and is only dissolved with difficulty, whilst if dilute alcohol is employed, small quantities of the vanadate are dissolved. The following method avoids these difficulties.

When the vanadic acid is present in the form of a pure alkaline salt, the solution, if not already neutral or alkaline, is mixed with ammonia and heated until colourless. The solution is cooled to 30-40°, mixed with powdered ammonium chloride until nearly saturated, then with four or five volumes of alcohol, and allowed to remain. If the solution is saturated with the ammonium chloride at a temperature not exceeding 40°, the alcohol precipitates only a small quantity of the salt, and this readily dissolves during washing. Care should be taken to avoid rubbing the sides of the vessel. The precipitate is collected and washed with alcohol.

If the solution contains salts which are only slightly soluble in alcohol, it is mixed with a slight excess of solid ammonium chloride, then with 4 or 5 vols. of a saturated solution of this salt, and allowed to remain for several hours. The clear liquid is decanted off through a filter, and the precipitate mixed with a fresh quantity of ammonium chloride solution, care being taken that a small quantity of the undissolved solid is always present. After remaining for some hours, the liquid is again decanted off, and this treatment is repeated two or three times according to circumstances. The filter is then washed with hot water to dissolve the adhering precipitate, and the solution is allowed to run into the beaker containing the bulk of the precipitate, which is partially dissolved, and the liquid now contains ammonium vanadate partly in solution, partly precipitated, but free from other salts. It is treated in the manner described above.

The washed ammonium vanadate is dried and heated in a platinum capsule until the filter burns, and is then kept in fusion until the precipitate is completely oxidised. In order to prevent the formation of V2O,V20s, the partially roasted precipitate is moistened with nitric acid, dried, and then fused.

When the vanadic acid is not present in combination with an alkali, the other metallic oxides must be removed by suitable methods, and the vanadic acid converted into an alkaline salt. C. H. B.

Determination of Nitrates in Well Waters. By L. SPIEGEL (Chem. Centr., 1887, 363-364).-Wagner's chromic oxide method (this Journal, 1871, 753) did not give satisfactory results. The most accurate is the Schulze-Tiemann method (this Journal, 1873, 529, and 1874, 91), but it is necessary that the end of the gas delivery tube should be plunged deep in the soda solution, that boiled ferrous chloride and hydrochloric acid should be used, and that the last traces of nitric oxide should be driven over into the measuring tube by

carbonic anhydride. Of the methods depending on reduction to ammonia, that of Harcourt and Siewert with König's modifications is the most suitable. Heating over the free flame, however, inevitably causes potash to be carried over.

Good results can be obtained by the Marx-Trommsdorf indigo process, if the nitrate solution used in standardising is of approximately the same strength as that to be tested. Nitrites have, for the same quantity of available oxygen, the same oxidising power as nitrates. Both of these methods are vitiated by organic matter.

A colorimetric process based on the blue coloration with diphenylamine in strong sulphuric acid gives a fairly accurate determination very readily. At least 9 volumes of sulphuric acid must be used for 1 volume of water. Organic matter is without influence, but ferric salts produce a blue colour by themselves and must be removed. M. J. S.

Detection of Cane-sugar, Glucose, and Dextrin in Wines. By TONY-GARCIN (Compt. rend., 104, 1002-1003).-The wine is decolorised by means of animal charcoal, and its rotatory power and reducing power are determined.

When the reducing power is equivalent to 2 grams or less, and the rotatory power is more than +13', the wine contains some foreign dextrogyrate substance. If the wine contains more than 2 grams of reducing matter per litre, 1-5 gram is deducted, and the remainder is multiplied by 6 and distinguished by the sign +. This is added algebraically to the observed rotatory power expressed in minutes, and if the sum is greater than +13', the wine probably contains foreign dextrogyrate substances, and this conclusion is certain if the excess above +13' is equal to 10'.

The nature of the foreign matter is determined by chemical methods; cane-sugar by inversion, dextrin by saccharification; glucose, in the absence of cane-sugar and dextrin, by the relation between the reducing action and rotatory power of the wine.

When polarimeters other than Laurent's are used, it may be taken that the rotatory power of wines free from foreign dextrogyrate matter is never more than +13'. C. H. B.

New Test for Coniferin. By H. MOLISCH (Chem. Centr., 1887, 366). An alcoholic 20 per cent. solution of thymol is diluted with water as long as it remains clear; an excess of solid potassium chlorate is added and after some hours the mixture is filtered. Coniferin, treated with a drop of this solution and two drops of strong sulphuric acid, acquires a fine blue colour when evaporated in direct sunlight. A wood section, or wood-pulp paper moistened with this solution, and a drop of hydrochloric acid rapidly becomes blue even in the dark. Since coniferin is only present in lignefied cell-walls, thymol may probably be of use in the microscopic detection of woodfibre. M. J. S.

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