METHODS FOR THE DETERMINATION OF VANADIUM. THE importance which has recently been attained by the element vanadium in metallurgy has caused considerable research into rapid and accurate means for its determina. tion. Two recently published volumetric methods are here given. The first of these was worked out by Mr. H. F. Watts of Boulder, Colo., and appeared in the Western Chemist and Metallurgist for November. The second is a colorimetric one devised by Mr. Arnold Wm. Gregory, an English chemist, and was published in a recent issue of CHEMICAL NEWS (see vol. c., p. 221). Fill a 500 cc. beaker half full of cold water and transfer the cold crucible containing the melt to it. Care should be taken at this point as the reaction between the peroxide and water is violent. It is well to float the crucible in the beaker, cover with a large watch-glass, and add water to the contents of the crucible a few drops at a time from a wash-bottle. When solution is complete, remove and wash the crucible, heat to boiling, and pass a current of carbon dioxide through the solution until saturated. Remove from the heat, allow to settle, and pour through a filter supported on a platinum cone. Wash three times by decantation and three times on the filter, using hot water containing a little sodium carbonate. Suction can be applied toward the end of the operation if found necessary. The filtrate is brought just acid with nitric acid, boiled, and the vanadium precipitated with lead acetate; the slight excess of nitric acid being corrected by the addition of a grm. or two of sodium acetate. The precipitate of vanadate of lead is separated by filtration, and dissolved in a small quantity of dilute nitric acid. To the solution add 10 cc. concentrated sulphuric acid, evaporate to fumes, cool, add cold water and separate the sulphate of lead by filtration, catching the filtrate in a flask. The filtrate, which may amount to 150 cc., is boiled and reduced by sodium sulphate, using I grm. and adding in successive small portions. The excess of sulphur dioxide is removed by boiling; for convenience in testing this point fit a stopper and delivery tube to the flask. When the escaping steam no longer decolorises a dilute solution of permanganate of potash, held in a small beaker, the boiling is stopped, and the hot solution titrated with standard permanganate. The iron factor multiplied by o‘916 equals vanadium. If the material contains arsenic it will be necessary to remove it. A convenient point at which to do this is after NEWS right strength. Heat the solution to boiling, and pass a current of carbon dioxide gas. From this point the method is carried out as described above. For Products containing much Silica, not readily decomposed by acids, the method of heating with sodium peroxide may be used, but in this case it will be necessary to remove the silica. The filtrate from the iron, after slight acidification with nitric acid, is made alkaline with ammonia, and 3 or 4 grms. of ammonium carbonate added. The beaker is put on a warm plate and allowed to stand for an hour with occasional stirring. The voluminous precipitate of silica is separated by filtration on a 12 cm. filter supported on a platinum cone, using suction. This precipitate, although somewhat inclined to be sticky, is not difficult to filter if suction is used. The washing with hot water, containing a little ammonium carbonate, must be thorough. Ten or twelve times is not too much, churning up the precipitate well with the stream from the wash-bottle. The filtrate now freed from the greater part of the silica is again made slightly acid with nitric acid, and the precipitate with lead acetate made as before. When using the acid method of decomposition, it is not always safe to assume that the vanadium is all extracted by treatment of the ore crushed to 80-mesh or coarser, with dilute nitric acid, as is sometimes recommended. Some vanadiferous sandstones yield to this treatment, but not all, and the writer has repeatedly found vanadium in residues treated in this manner. To make sure of complete extraction the ore should be finely ground in an agate mortar and decomposed first with aqua regia. The direct reduction and titration of the vanadium in the presence of the accumulated salts of the analysis is inaccurate, the end-point being uncertain and successive reductions generally failing to check; so it is always necessary to separate the vanadium from these by precipitation with lead acetate, the titration of pure vanadium solutions being exact. If rapid approximate results are wanted, the filtrate from the iron residue may be acidified with sulphuric acid and the solution reduced and titrated. The method as described has the advantage over the ammonium carbonate method in that the separation of the iron and vanadium is performed, in nearly every case, at a single operation, and obviates the necessity of a resolution and re-precipitation of the iron residue. A clean separation can be made on iron vanadate, using 300 mgrms. of substance. The carbon dioxide is used to prevent bumping, although in some cases its use apparently gives a cleaner separation, due possibly to the tendency of the alkaline carbonates formed to hold vanadium in solution. Engineer, x., No. 6. The Chemical PROCEEDINGS OF SOCIETIES. ROYAL SOCIETY. Ordinary Meeting, January 13th, 1910. the first reduction by sodium sulphite. Pass hydrogen Sir ARCHIBALd Geikie, K.C.B., President, in the Chair. sulphide, filter, boil out excess, and titrate. A correction from the burette reading should be made as follows:-To 150 cc. of water in a flask add 10 cc. sulphuric acid and I grm. sodium sulphite. Boil out the sulphur dioxide and titrate. The amount of permanganate used to colour the solution should be deducted from the assay. This correction usually amounts to 0.2 cc. Method for Ores.-Treat 1 grm. of the finely ground ore (less if high grade) with 10 cc. of aqua regia, and evaporate to dryness. Add 10 cc. nitric acid, 120 specific gravity, and digest on the hot plate for a few minutes. Filter off the silica, &c. Nearly neutralise the filtrate with caustic soda, and pour it with constant stirring into a hot solution of caustic soda contained in a large beaker. A stick of caustic soda dissolved in 200 cc. of water is about the CHEMICAL NEWS, " SIMPSON. This paper relates to measurements of the electricity of rain made in continuation of those described at the beginning of last year (Phil. Trans., 1909, Series A, ccix., 379-413); and, in addition, to a series of measurements of the electricity of snow made during the winter of 1908-09. Electricity of Rain and Snow.” By Dr. G. C. | from acetylene tetrabromide, is very stable and forms characteristic crystals. Alkaline mercury cyanide solution gives with dichlorethylene a good yield of mercuric chlor acetylide, Hg(C: CCI)2, which, when warmed with potassium cyanide and caustic potash, liberates perfectly pure chloracetylene. Bromacetylene can be prepared similarly. Both substances yield metallic compounds similar to those obtained with acetylene, and there seems to be no reason for rejecting the usual formulæ CH CC1 and CH CBг. Besides the normal silver, copper, and mercuric salts, monochloracetylene yields trichlormercury- acetic acid, (CIHg)3C.CO2H, with mercury chloride. When chloracetylene is led into ammoniacal silver.nitrate solution, the white precipitate obtained very readily turns brown in air, and after being dried explodes. With cold saturated mercury chloride solution chloracetylene gives tris-chlormercury-acetic acid, (CIHg)3C.CO2H. All the main conclusions drawn from the previous work have been confirmed, and it may now be stated with confidence that in Simla (a) More than three times as much positive as negative electricity is brought down by the rain. (b) The heavier the rainfall, the more likely is it to be positively charged. (c) Light rain is, as a rule, more highly charged than heavy rain, irrespective of whether the charge is positive or negative. With regard to the electrification of snow the measurements indicate that in Simla (d) The positive charge carried down by the snow is between three and four times as great as the negative charge. (e) Snow is generally more highly charged than rain. "Polarisation of X-rays compared with their Power of Exciting High Velocity Cathode Rays." By L. VEGARD. Osmium.-A. Gutbier and K. Maish.-Pure osmium metal was converted into sodium hexachloro-osmate, and by double decomposition with alkaline chlorides the rubidium and cæsium hexachloro-osmate were obtained. They form octohedral crystals of the regular system, which are soluble in cold water. The pure aqueous solutions decompose very readily in air, becoming darker, until finally a fine black powder separates. They dissolve in dilute hydrochloric acid, giving stable solutions from which they can be re-crystallised. The compounds are anhydrous and are stable in dry air. They correspond in chemica! behaviour to the hexachloroplatinates, as well as in thei. CHEMICAL NOTICES FROM FOREIGN crystallographic character. NOTE-All degrees of temperature are Centigrade unless otherwis expressed. Comptes Rendus Hebdomadaires des Séances de l'Académie des Sciences. Vol. cxlix., No. 21, November 22, 1909. New Syntheses of Vanilline.-A. Guyot and A. Gry.-Mesoxalic ether or any aß-diketonic ether, when added to a solution of zinc chloride in acetic acid, gives condensation products, e.g., methyl paraoxymetamethoxyphenyltartronate, which are transformed quantitatively into vanilloyl carbonic acid by oxidation, and the acid can be decomposed into vanillin and carbon dioxide by any of the methods described by Tiemann, Gassmann, or Bouveault. The yield of vanillin is good (70 to 80 per cent of the theory), and the substance is obtained in the pure state, quite free from isomers and resinous matter. Condensation Products of Camphor. - Marcel Guerbet.-Montgolfier has shown that when the mixture resulting from the action of sodium on a toluene solution of camphor is heated to 280° in a closed vessel, a certain proportion of campholic acid is formed together with neutral oily substances. Montgolfier thought that they consisted of colophenic hydrocarbons, (C10H16)n, but when they are subjected to fractional distillation, products are obtained which contain too much oxygen to be derived from colophene. The fractions which pass over between 326° and 335° give crystals from which definite compounds C20H300 and C20H32O can be separated. C=C first is bornylene camphor, C8H14 do CH2 CH-CH The > C8H14 Platinum.-A. Gutbier and Fr. Bauriedel.-If a solu tion of an organic ammonium bromide is added drop by drop to a solution of hydrogen platinum bromide, and the crystalline precipitate re-crystallised from hydrobromic acid, the hexabromoplatinates are obtained in the pure state. Their melting-points could not be determined with absolute certainty, as the substances liquefy only at very high temperatures and begin to change colour previously. They usually dissolve in water at the ordinary temperature, giving beautiful red liquids, and can be re-crystallised from unless a small quantity of hydrobromic acid or water is water. They are practically insoluble in absolute alcohol present, when again they form red liquids. All solutions are yellow when diluted. Concentrated caustic soda in excess colours the solutions yellow; they become colourless on warming. Ammonia produces at the ordinary temperature a yellow coloration which disappears on warming. Hydrazine hydrate decolorises the solution at the ordinary temperature, platinum being separated and nitrogen evolved. Molecular Weight of Caoutchouc in Latex.-F. Willy Hinrichsen and Erich Kindscher. The determination of the molecular weight of caoutchouc in benzene solution by the method of the lowering of the freezingpoint gives the value 3173 for the molecular weight. This is only the lower limit, for it is possible that in the latex some constituents soluble in benzene are present which would lower the freezing-point. This result appears to show that Weber's theory of the polymerisation of a hydrocarbon of low molecular weight is incorrect, and that the original caoutchouc possesses a very high molecular weight. Reaction for Polybasic Acids and a New Reaction for Titanium. - Jean Piccard. In reductions with titanium trichloride certain acids act as catalytic agents to while the second is C8H14 CO CHC8H14, obtained accelerate the reaction, and it is found that, in general, monobasic acids have no action, while polybasic act as catalysers. Hence this reaction can be used as a test of the basicity of an acid. It is interesting to notice that hydrofluoric acid is very strongly active, which confirms the assumption of the polymerisation of the acid to form H2F2 molecules. It is already known that the salts of trivalent titanium give with oxalic acid in aqueous solution a yellow coloration. Pyrocatechin also gives an orangeyellow coloration with titanium trichloride, and this colour Messrs. reaction is much more marked than that with oxalic acid. If the dilution is not too great, a red-brown amorphous precipitate is obtained, forming a black insoluble powder LONGMANS & CO.'S LIST. on drying. It appears to be a mixture of various com. pounds. If the dilution is greater the formation of the yellow coloration is a very sensitive test for titanium, fifteen times as sensitive as the hydrogen peroxide reaction. Pyrocatechin must be present in excess, and mineral acids prevent the reaction, while alkalis, alkaline carbonates, or ammonia weaken it. Preparation of Colloidal Solutions of Metals by Ultra-violet Light.-The Svedberg.-If a metal, the surface of which has been freed from a layer of oxide, is placed in a shallow dish, covered with a dispersion agent, and subjected to the radiation of a quartz mercury lamp, after a few minutes the liquid shows under the ultra-microscope the characteristic appearance of a colloidal solution. Different metals behave differently in different dispersion agents. Silver, copper, tin, and lead very readily yield colloidal solutions, particularly the last-named, while platinum, aluminium, and cadmium show no tendency to form them. Existence of True Percarbonates and the Difference between them and Carbonates with Hydrogen Peroxide of Crystallisation.-E. H. Riesenfeld and B. Reinhold. By the electrolysis of a solution of potassium carbonate under suitable conditions, anhydrous, nearly pure, potassium percarbonate can be prepared. When concentrated neutral potassium iodide solution is added to percarbonates, iodine instantly separates, while the hydrogen peroxide addition products of the carbonates are decomposed by this reagent giving off oxygen. This reaction can be used to distinguish percarbonates and peroxides. True percarbonates are formed only by the electrolysis of alkali carbonate solutions. All the salts hitherto obtained by the action of hydrogen peroxide on alkaline carbonates appear to be carbonates with hydrogen peroxide of crystallisation. MEETINGS FOR THE WEEK. RECENT ADVANCES IN PHYSICAL AND By A. W. STEWART, D.Sc., Svo. 7s. 6d. net. RECENT ADVANCES IN ORGANIC CHEMISTRY. By A. W. STEWART, D.Sc., Lecturer on Stereochemistry in University College, London. With an Introduction by J. NORMAN COLLIE, Ph.D., LL.D., F.R.S., Professor of Organic Chemistry in University College, London. 8vo. 7s. 6d net. "To anyone who has knowledge enough to know of the vast extent of this subject, but not a courage sufficiently brave to attack it, we would advise him to peruse this excellent work."- Chemical Trade Journal. THE FUNDAMENTAL PRINCIPLES OF CHEMISTRY. An Introduction to all Text-books of Chemistry. By WILHELM OSTWALD. Authorised Translation by HARRY W. MORSE. 8vo. 7s. 6d. net. A DICTIONARY OF APPLIED CHEMISTRY. By T. E. THORPE, C.B., F.R.S., Phil.D., D.Sc., &c. Complete in Three Volumes, Half-bound. Vol. I., with 239 Illustrations, 8vo., £2 2s. Vol. II., with 240 Illustrations, 8vo, £2 2s. Vol. III., with 352 Illustrations, 8vo., £3 3s. THE PRINCIPLES OF CHEMISTRY. By D. MENDELÉEFF, Professor of Chemistry in the University of St. Petersburg. THIRD ENGLISH EDITION. Edited by THOMAS H. POPE, B.Sc., F.I.C. With 110 Illustrations. 2 vols. 8vo. 32s. net. MONDAY, 24th.-Royal Society of Arts, 8. (Cantor Lectures). "Tex- HIGHER MATHEMATICS FOR STUDENTS OF tile Ornamentation," by Alan S. Cole, C.B. TUESDAY, 25th.-Royal Institution, 3. "The Cultivation of the Sea," by Prof. W. A. Herdman, F.R.S., &c. WEDNESDAY, 26th.-Royal Society of Arts, 8. "Goldsmiths' and JUST PUBLISHED. Demy 8vo, 168 pp., 109 Illustrations. 8/6 net. MODERN COKING PRACTICE Including the ANALYSIS of MATERIALS and PRODUCTS. A Handbook for those engaged in Coke Manufacture and the Recovery of By-products. By T. H. BYROM, F.I.C., F.C.S., Mem. Soc. Chem. Industry, Chief Chemist to the Wigan Coal and Iron Company, and J. E. CHRISTOPHER, Mem. Soc. Chem. Industry, Lecturer on Coke Manufacture at the Wigan Technical College. LONDON CROSBY LOCKWOOD & SON, 7, STATIONERS' HALL COURT, E.C., and 121A, VICTORIA ST., S.W. CHEMISTRY AND PHYSICS. With special reference to Practical Work. THIRD EDITION, Enlarged. With 189 Diagrams. 8vo. 15s. net. A TEXT-BOOK of PRACTICAL PHYSICS. A Book of Reference for the Student working in a Physical Laboratory. With 278 Illustrations Large cr. Svo 10s. 6d. WORKS by G. S. 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Berthollet was led to the subject by the views held at that time regarding the nature of acids. These are clearly set out by Lavoisier in his "Elementary Treatise on Chemistry" ("Traité Elementaire de Chemie," 1789, vol. i., p. 5), where, referring to the formation of acids in general, he says:-"One sees that oxygen is a principle common to all, and is that which constitutes their acidity. They are therefore differentiated one from the other by the nature of the acidified substance. It is necessary then to distinguish in every acid the acidifiable basis to which M. de Morveau has given the name of 'radical' and the acidifying principle, that is to say, the oxygen." Berthollet, having discarded the phlogiston theory, thought it of interest to subject "dephlogisticated marine acid, as he termed chlorine, to fresh experiments, thinking the results might confirm the new views. He read an account of his work at a meeting of the Institute held on April 6th, 1785, and published it, together with some new observations and replies to some objections which had been made to his conclusions, under the title "Memoire sur l'acide marin déphlogistique ("Memoires de l'Academie Royale for the Year 1785,” Paris, 1788, pp. 276-295; translated in Alembic Club Reprints, No. 13, PP. 10-31). Berthollet added much to what was then known respecting the properties of chlorine, and thought that his experiments proved that it was a compound of oxygen and hydrochloric acid. He based this conclusion upon two facts; the first, that when manganese dioxide is heated, it loses oxygen and then yields much less chlorine than before when a given weight is treated with hydrochloric acid; the second, that when a solution of chlorine water is exposed to sunlight, oxygen is liberated and hydrochloric acid produced. He writes thus :-"I calcined some manganese at a strong heat, and extracted from it a large quantity of vital air; it lost one-eighth of its weight. In this state I treated it with marine acid, and obtained from it a much smaller quantity of dephlogisticated marine acid. The formation of dephlogisticated marine acid is due, there fore, to the vital air of the manganese which combines with the marine acid." He then describes a second experiment: -"I saturated distilled water with dephlogisticated marine acid the thermometer was at 18° with this liquid I filled a bottle communicating by means of a tube with an apparatus for collecting gas: this bottle with the tube, which was itself filled with the liquid, was of the capacity of 51.5 cubic inches. I exposed it to sunlight, and soon saw a large quantity of small bubbles of air become dis In Hydrochloric acid has received a variety of names. It was originally known as spirit of salt (spiritus salis Glauberianus). Scheele terms it spiritis salis, or acidum salis, or saltsyra indifferently. It received in Germany the name "salt acid" (salzsaure), or sometimes sea-salt acid" (Meersalzsaúre). This in France became, by dropping the really distinctive part, "marine acid " (acide marin). the reformed nomenclature introduced about 1787 by Lavoisier in conjunction with de Morveau, Berthollet, and Fourcroy, this absurd name was very properly altered to one which it long bore, and by which it is still occasionally known, muriatic acid (acide muriatique), derived from the Latin word muria, an old name for sea-salt, This name was first suggested by Bergman. engaged, which on being collected in a bottle filled with inches, the thermometer being at 17°. The dephlogisticated marine acid gradually lost its colour, and the colourless liquid thus formed no longer destroyed blue vegetable colours but reddened them strongly, and like ordinary marine acid produced an effervescence with fixed alkalis. The dephlogisticated marine acid was indeed almost entirely reduced to ordinary marine acid, although it still retained a scarcely perceptible suggestion of the original odour." After describing an estimation by silver of the quantity of acid present in the liquid, he continues :-"The air which was disengaged from the dephlogisticated marine acid having been put over a solution of liver of sulphur, was absorbed, leaving a residue measuring one cubic inch; so that it consisted of vital air mixed with one-fifteenth its bulk of azotic gas, the latter being, without doubt, due to some atmospheric air which would be disengaged both from the water and from the apparatus which I employed." Then, after considering the relative amounts of hydrogen chloride and oxygen produced, he adds:"These experiments ought to remove any remaining doubts as to the nature of dephlogisticated marine acid; it is manifestly formed by the combination of vital air with marine acid, but in it the vital air adheres so feebly to the marine acid that the action of light suffices to disengage it. . . . Dephlogisticated marine acid dissolves iron and zinc without any gas being disengaged, and in the same manner as water dissolves salt; for in order that these metals should dissolve in an acid, it is only necessary that they should unite with a portion of vital air, as M. Lavoisier has proved; and as dephlogisticated marine acid can furnish them with the vital air necessary, there is no decomposition of water, and no inflammable air is produced when it dissolves them." At that time it was not recognised that acidic oxides combine with a portion of the water in which they dissolve, yielding acids, but the acidic oxides in solution were thought to combine directly with metallic oxides to form salts. According to Berthollet's views, therefore, when metals dissolved in dephlogisticated marine acid, it was the oxygen of the latter which oxidised them, the basic metallic oxides thus produced then combining with the supposed acidic oxide marine acid formed at the same time. When, however, metals dissolved in aqueous marine acid, the water played a part, and supplied the oxygen to the metal while its hydrogen was liberated. The theory explained satisfactorily most of the facts then known; for example, Berthollet states:-"If a morsel of phosphorus is put into dephlogisticated marine acid (evidently a solution in water is meant) and exposed to light, the colour and odour of the acid soon disappear. The resulting liquid reddens blue vegetable colours, and lime-water precipitates calcareous phosphate from it, so that phosphorous combines with the vital air of dephlogisticated marine acid and becomes phosphoric acid." Not the least of the services which chemistry owes to Lavoisier and his three contemporaries - Guyton de Morveau, Berthollet, and Fourcroy-who first accepted and helped to promulgate his views, is their successful reform of the nomenclature, based upon the principle of making the name indicate the qualitative composition of the substance. Using the name muriatic acid, which had already taken the place of the older "spirit of salt," de Morveau suggested in a paper read before the Academy on May 2nd, 1787, that the term oxygenated muriatic acid should be adopted for chlorine instead of dephlogisticated marine acid, as the latter involved a conception of its composition at variance with the newer views. Muriatic acid itself was regarded at this time as an oxide. Lavoisier says ("Traité Elementaire de Chemie," Paris, 1789, chap. vi., p. 75) :— "Although no one has yet succeeded in composing or decomposing the acid obtained from sea-salt, there is no 38 New Method of Estimating Chlorates in presence of Nitrates. (CHEMICAL NEWS, doubt that it is formed like all others by the union of an Chlorine was thus, in his opinion, a more highly oxidised compound of the "radical muriatique," but he clearly recognised that there was a difficulty in adopting this view, for he adds: : "Muriatic acid presents one remarkable characteristic. Like sulphurous acid and several others it is susceptible of a higher degree of oxidation, but the excess of oxygen produces in it an effect entirely contrary to that which it produces in sulphurous acid. The addition of oxygen changes sulphur into a gaseous volatile acid, soluble only to a slight extent in water, while the further addition of oxygen converts this into sulphuric acid, an acid which displays much more marked acid qualities, which is much more stable, which cannot exist as a gas, which has no smell, and which mixes with water in any quantity. The Jan. 28, 1910 In this journal Gay-Lussac and Thenard published an account of their work, the results having been discussed at Arcueil, and afterwards communicated to the Institute at a meeting held on February 27th, 1809. A NEW METHOD OF ESTIMATING By TARAK NATH DAS, B.Sc. THE volumetric estimation of chlorates by their oxidising action may be classified under three heads: - (a) Chlorates may be reduced to chlorides which are estimated by N/10 AgNO3 (Mohr); (b) certain reducing agents in excess are made to act upon chlorates, this excess being afterwards exactly determined; (c) chloric acid is reduced to lower oxides of chlorine which liberate from KI an equivalent amount of I, this being estimated by N/10 Na2S2O3 (Bunsen). The presence of some soluble oxidising agents During the closing years of Berthollet's life, when he was residing at Arcueil, a small village about three miles from Paris, meetings attended by the most eminent scientific men of the day were held regularly at his house, the papers read there being afterwards published in a journal appearing between 1807 and 1817 called Mémoires de Physique et de Chemie de la Société d'Arcueil.† English chemists, following a suggestion of Kirwan, adopted the shortened form "oxymuriatic acid" in place of this. The original members of the Society of Arcueil were Laplace, C. L. Berthollet, Biot, Gay Lussac, Humboldt, Thenard, Decandolle, Collet-Descostils, and A. B. Berthollet, while Arago, Berard, Chaptal, Dulong, Malus, and Poisson joined later. (b) would seriously interfere with the methods under (b) and (c). The most expeditious processes known under (a) are those of Gladstone and Tribe's zinc-copper couple (as modified by Bothamley and Thompson, Trans., 1888, liii., 164), and Fresenius's "Hydrated Protoxide of Iron" (vide Fresenius's "Quantitative Analysis," i., §150d, Seventh Edition). Non-contamination with chlorides in these reagents is very necessary; in the former, in the sodium carbonate used to precipitate zinc; in the latter, in caustic potash. The problem therefore suggests itself whether an iodometric estimation of chlorates could be effected in the presence of nitrates, &c., with considerable accuracy. In this connection the author has found that when an alkaline solution of stannous chloride is boiled with an excess of potassium chlorate, the former is completely oxidised to the stannic state. As atmospheric air has a similar oxidising action, it is evident that all air must be driven out of the apparatus by a current of hydrogen gas. The necessary operation may be performed in a small round-bottomed flask (arranged as shown in the figure) containing a weighed quantity of KCIO3, a few lumps of pure caustic soda, and a known volume of SnCl2 solution. The tube A is used for leading a current of hydrogen gas |