THE ANALYST. 167 INORGANIC ANALYSIS. The Reduction of Lead &om Lead Oxide in Assaying, and the Advantages of an Oxidizing Slag. (Trans. Amer. Inst. Min. Eng., New York Meet. ; through Chem. Zed. Rep., xxviii., 54.)-In a systematic study the authors found that the action of potassium nitrate and lead oxide on sulphide ores varied largely according to the other ingredients of the slag. Thus, the addition of silica, and borax was found inadmissible, borax especially preventing the oxidation of the ore. In presence of sodium bicarbonate, on the other hand, good results are obtained, agreeing well with those given by the older methods. For the actual assay by this method, 4 assay ton ore, 70 grammes red lead, 15 grammes bicarbonate, and as much saltpetre (ascertained by a preliminary trial) as will give a lead button weighing 20 grammes.The charge is placed in Battersea pots holding 10 to 20 grammes, and run down in a, muffle heated to about 900" C., the fusion requiring 15 to 20 minutes. E. H. Miller, E. J. Hall, and M. J. Falk. A. G. L. Note on a Method of Determining Small Quantities of Mercury. Theodore William Richards and Sidney Kent Singer. (Jozirn. Amer. Chem. SOC., xxvi., 300.) -Mercury can be quantitatively separated from cadmium by immersing in the neutral solution, which preferably contains the metals as nitrates, a coil of copper wire, on which the mercury is deposited. Before being used the copper wire should be cleaned with alkali, k i d , and water successively. After the mercury has been deposited, the coil is washed with water and alcohol, dried over calcium chloride, and weighed.I t is then heated at a temperature a little above 350' C. in a current of hydrogen and re-weighed, the loss in weight being due to the mercury. I n practice it is found best to use two coils for each determination, allowing the first to remain in the liquid until the bulk of the mercury has been deposited, and then inserting the eecond to remove the last traces. For quantities of about 0.03 gramme of mercury the best results appear to be obtained by leaving the first coil four to five hours in the solution, and the second coil twenty hours. The test results given are satis- factory. A. G. L. On a Simple Method for the Determination of Arsenic in Hydrochloric Acid and Sulphuric Acid. (Chem.Zeit., xxviii., 211.)-The method depends on the fact that when potassium iodide is added to sulphuric or hydrochloric acid containing arsenic in either state of oxidation, arsenious iodide is formed, which is insoluble in fairly concentrated acids, but soluble in water. The presence of chlorine, ferrio chloride, or selenium exerts an injurious influence on the reaction, but this may be obviated by adding a few drops of a strong solution of stannous chloride in hydrochloric acid (specific gravity 1.175) just before adding the potassium iodide. To determine arsenic in hydrochloric acid, 50 C.C. of the acid of specific gravity 1.17 to 1.18 are taken; should the acid be weaker, it is brought to this strength by the addition of sulphuric acid (specific gravity 1.45).Five C.C. of N. U. Blattner and. J. Brasseur.168 THE ANALYST. 30 per cent. potassium iodide solution are then gradually added, with constant stirring. After standing for one minute, the liquid is filtered through glass wool or cotton wool, the filtrate being tested for arsenic by adding more potassium iodide. The precipitate is then washed with pure strong hydrochloric acid, to which 10 per cent. of the potassium iodide solution bas been added, after which it is dissolved in water, the solution made alkaline with sodium bicarbonate, and titrated with iodine solution. I n the case of sulphuric acid, 25 C.C. of the acid, which should have a speoific gravity of 1.45, are taken ; to prevent the precipitation of any lead iodide, 25 C.C. of concentrated hydrochloric acid are then added, after which the procedure is the 8ame as for hydrochloric acid, The method is said to give good results with quantities of arsenic up to 0.20 per cent., the values obtained in the case of small amounts being accurate to 0.001 per cent. A.G. L. The Volumetric Determination of Arsenic and Antimony in Nickel Ores. H. Nissenson and A. Mittasch. (Chem. Z e d . , xxviii., 184.)-The method is a modification of Nissenson and Siedler's method (ANALYST, xxviii., 324) applicable to the determination of both arsenic and antimony. I n a 250 C.C. flask, 0.5 gramme of finely powdered ore is heated with 8 C.C. of concentrated sulphuric acid for several hours, until the mass becomes completely white or light-yellow; 50 to 100 C.C. of water are then added, the liquid is boiled until all basic salts are completely dissolved, and, without previous filtration, treated with hydrogen sulphide.The sulphides of arsenic, antimony, and copper obtained are filtered off together with the insoluble residue, washed back into the original flask, and dissolved by heating for several hours with 7 C.C. of concentrated sulphuric acid. The solution, which contains arsenic and antimony in the lower state of oxidation, is then diluted with about 100 C.C. of water, heated to boiling, and titrated with & potassium bromate solution, using 3 drops of indigo solution as indicator ; the indigo is preferably added only just before the end of the titration, if the amount of arsenic and antimony present is known approximately. To the titrated liquid a little more potassium bromate is added; after evapora- tion to a very low bulk it is then treated with tartaric acid, an excem of ammonia, and magnesia mixture to separate the arsenic. After long standing the precipitate is filtered off and washed slightly with ammonia; the filtrate is acidified with sulphuric acid, and freated with hydrogen sulphide, the sulphide precipitate being dissolved and titrated as before, giving the quantity of antimony present.The arsenic is obtained by difference. Results obtained in this way are always slightly high as regards antimony, the arsenic not being quite completely separated as magnesium ammonium arsenate. To eliminate this error a constant correction may be applied to the results; or the sulphide precipitate obtained after the removal of the arsenic may be extracted with ammonium carbonate to remove the last traces of arsenic ; or else another portion of the ore may be dissolved in brominated hydrochloric acid, which volatilizes the arsenic, and the antimony determined in the solution, either by electrolysis or by titration with bromate, after reduction with sodium sulphi te.A. G. L.THE ANALYST. 169 The Colorimetric Determination of Chromium. A. Moulin. (Bidl. SOC. Chim., 1904, xxxi., 295-296.)-This process is based.on the fa&t recorded by Cazeneuve that the acetate of diphenylcarbazide gives a purple coloration with chromic acid and chromates. The reagent is prepared by dissolving 2 grammes of diphenylcarbazide in a mixture of 100 C.C. of 90 per cent. alcohol and 10 C.C.of acetic acid on the water- bath, and diluting the solution to 200 C.C. with alcohol of the same strength. The standard solutions of chromic acid used for the colorimetric comparison contain 0.50 gramme or 0.05 gramme in a litre. I n the determination, from 0.25 to 0.5 gramme of the sample is dissolved, chromium salts being converted into chromates in the usual way. I n the case of chrome iron the solution is oxidized by boiling with hydrogen peroxide in the presence of an excess of potassium hydroxide, the precipitated metals separated by filtration, and the filtrate and washings neutralized with acetic acid and diluted to 100 or 200 C.C. Portions of 1, 1.5, 2 c.c., etc., of the standard chromic acid solution are then introduced into a series of test-tubes, each of which contains 2 C.C.of the reagent and about 70 C.C. of water, whilst corresponding quantities of the solution under examination are introduced into a similar series of tubes. The liquids are diluted to 100 c.c., allowed to stand for twenty minutes, and the colours matched. The author states that this method yields very exact results, but that it is essential to have an excess of diphenylcarbazide. C. A. M. The Precipitation of Magnesium Oxalate with Calcium Oxalate. Nicholas Knight. (Chenb. News, lxxxix., 146.)-From analyses of dolomite made by different students the author comes to the conclusion that the magnesium precipitated with the calcium varies from an inappreciable amount (0.18 per cent. MgO) to a con- siderable quantity (1.20 per cent.MgO). He therefore recommends always to dissolve the unwatlhed precipitate of calcium and magnesium oxalates in hydrochloric acid, and reprecipitate the calcium with ammonia. A. G. L. The Use of Organic Magnesium Compounds in Analytical Operations. L. A. Tchongaeff. (Joiiru. SOC. Phys. CILim. B., xxxiv., 652 ; through Chem. News, Ixxxix., 139.)-Organic magnesium compounds of the type RMgI, where R represents an organic radical-e.g., CH,-are decomposed by water according to the equation : With organic compounds containing the hydroxyl group they react similarly. The author has consequently used the methyl derivative CH,MgI both for the recognition of the hydroxyl group, CH, being evolved, and as a means of separating bodies con- taining hydroxyl-e.g., alcohols, from other volatile substances--e.g., hydrocarbons.I n the last case, the alcohol is treated with an ethereal solution of CH,MgI, when it is converted into a non-volatile compound of the type ROMgI, whilst the hydrocarbon is not changed, and can be separated by distillation. RhlgI + H,O = R E + MgIOH. A. G. L.170 THE ANALYST. Some Applications of the Theory of Eleotrolysis to tbe Sepazation of Hetale from one another. (Chem. News, lxxxix., 110, 125.)-The author proposes to overcome the difficulties met with in the electrolytic separation and deposition of metals having higher polarization potentials than hydrogen (1) by reducing the resistance of the bath by the suppression of the formation of gae at the anode ; (2) by using cathodes of other metals besides platinum ; and (3) by forming complex salts.The first principle can be carried out in two ways : either by adding a reducing agent to the bath, or else by using a, soluble anode. For example, nickel can be separated from zinc in a solution containing ammonium sulphate and magnesium sulphate, to which sulphurous acid and an excess of ammonia is added; the operation is carried out at 90° C. Nickel can also be separated from zinc by using a zinc anode placed in a solution of magnesium sulphate, which is separated by a porous mem- brane from the solution containing the nickel and zinc, to which a large excess of ammonium sulphate and ammonia is added. A platinum cathode is placed in this liquid and connected by a metallic conductor with the zinc anode, no extraneous current being necessary.The solution should be heated nearly to boiling during the electrolysis. The polarization potential of metals which, using a platinum cathode, have a higher potential than hydrogen, can also be lowered below that of hydrogen by choosing a suitable metal for the cathode ; but in this case it must be remembered that as soon as the metal to be deposited covers the cathode, the latter behaves as though it consisted of this metal, so that the precipitated metal itself must possess the property of raising the polarization potential of hydrogen to the necessary degree. In this way lead, tin, and cadmium may be deposited from acid solutions, and cadmium may be separated from zinc, also in acid solution, by using a platinum cathode previously coated with tin or cadmium.The formation of complex ssllts has been already studied by Freudenberg (Zed. P'hys. Cliem., xiii., 97). The separation of tin and antimony in a solution contain- ing sodium hydrogen aulphide is an example, the tin passing into the state of a complex ion. Practically all the above methods are only approximstely quantitative, and require further working out. A. Hollard. A. G. L. The Direct Determination of Potassium in the Ash of Plants. Edward Murray East. (Joum. Anter. Chew. SOC., xxvi., 297.)-The ash from 2 or 3 grammes is prepared by moistening the sample with a 20 per cent. ammonium nitrate solution, drying, and incinerating for two hours at a temperature just below a red heat. The ash is transferred to a beaker with a few drops of hydrochloric aoid, the solution is heated to boiling, and 3 to 5 C.C.of barium hydrate solution, saturated at 32" C., are added. After one hour's digestion, the liquid is filtered hot, hot water also being used for the washing. The barium is next precipitated as sulphate by means of a iodhrn sulphate solution equivalent to the barium hydrate solution used. After five hours the liquid is filtered, and the filtrate evaporated down to 25 C.C. in a platinum dish. A drop or two of hydrochloric acid and the calculated amount ofTHE ANALYST. 171 platinic chloride necessary to convert all the alkalies into the chloroplatinates are added, and the determination is completed as in the Lindo-Gladding method. The method gives cloeely agreeing results, and requires much less time than the older methods.A. G. L. A Study Silberberger. sulphuric acid of the Quantitative Determination of Sulphuric Acid. Richard (Mowtshefte f. c'Jiei)i., xxv., 220.)-The author finds that when - - is precipitated in the presence of ferric salts with barium chloride, a, part remains in solution as a complex ferric-sulphuric acid, whilst some of the iron is thrown down in the form of the salt Ba,Fe,(SOJ6. If potassium nitrate is present in the solution during precipitation, the barium sulphate is contaminated by the double salt KBa,(NO,)(SO,), ; in the presence of potassium chloride the' salt KBa,Cl(SO,), is formed. In any case, barium sulphate is quite appreciably soluble in acid liquids, so that, if the precipitate obtained as usual is purified by treatment with hydrochloric acid after ignition, the results obtained are always too low unless the barium sulphate dissolved in the original filtrate is recovered by evaporation. On the other hand, when sulphuric acid is precipitated by means of an alcoholic 10 per cent. solution of strontium chloride, a volume of alcohol equal to twice the volume of the original liquid being then added, strontium sulphate is precipitated quantitatively in a pure condition. The author therefore proposes to use this method of determining sulphuric acid, especially for the andysis of pyrites and other metallic compounds, such as chromium and zinc salts. .4. G. L.