THE ANALYST. 17 INORGANIC ANALYSIS. The Assay of Telluride Gold Ores. C. H. Fulton. (School of Miizes QzmrterZy, 1898, xix., 419-426.)--From the results of a series of experiments on the assay of gold ores containing tellurium, the author has come to the following con- clusions: In order to obtain good results, it is essential to have a large excess of litharge, but in the case of rich telluride ores this should be obtained by reducing the amount of ore, rather than by increasing the litharge, since otherwise the lead button may be too large to cupel directly. I n the crucible assay, with direct cupel- lation, which is considered the best, the fire should be moderately hot, and the length of time in the furnace should be from forty to fifty minutes. The assay should be conducted so as to give a button of good size (from 20 to 28 grammes).The cupella- tion should be made at a low heat with crystals of litharge forming on the cupel, and in accurate assays the crucible slag should be Te-melted, the button cupelled, and the amount of gold added to the first assay. Scorification of any kind leads to bad results with telluride ores, and the loss of gold on cupelling a large or brittle button directly is much less than if it were first rescorified. The amount of gold lost in the slag on scorifying directly is very great, amounting to as much as 5-6 per cent. in the assays described. The loss of gold in a rich telluride ore is greater than in a, low-grade ore, but the percentage of loss decreases with the richness of the ore. These conclusions agree with the experience of F.C. Smith, who found that the loss of gold in the assay of ores containing tellurium was very great, if the charge was not prepared with the correct proportion of litharge. C. A. M. Separation of Zinc, Copper, Mercury, or Bismuth from Aluminium. F. S. Havens. (Zeits. aizorg. Chenz., 1898, xviii., 147.)-The process which the author has already described (ANALYST, xxii., 194, and xxiii., 109) for the precipitation of aluminium chloride in presence of ether and hydrochloric acid, is equally available for the removal of the other metals mentioned in the title. The residual zinc chloride is preferably converted into nitrate by repeated evaporations with nitric acid, then ignited in a platinum crucible and weighed as oxide. Copper is converted into sulphate, rather than nitrate, and also weighed as oxide.The figures recorded by the author in two tables are highly satisfactory, showing maximum errors of - 1.3 and + 0.9 milligrammes in estimating about 0-5 gramme of alumina ; - 0.8 and + 0.4 milligrammes (corrected) in the direct estimation of the accompanying zinc oxide (0.1 to 0.2 gramme) ; and - 0.7 and + 1.3 rnilligrammes in the case of copper oxide; while all the mean results are practically identical with those demanded by the theoretical composition of the several mixtures analysed. F. H. L.18 THE ANALYST, Analysis of Ferro-Tungsten. A. G. McKenne. (Proc. Eng. Xoc. IVestern Peunsylvania, 1898, xiv., 171.)-0*5 gramnie of the finely-powdered sample is mixed with 3 grammes of sodium peroxide in a copper* crucible, and the mass is raised for a minute to a dull-red heat, holding the crucible in tongs so as to agitate its contents and prevent the alloy from sinking to the bottom.The melt is extracted with water, a few C.C. of alcohol added to render manganese insoluble, and the whole filtered. The filtrate, containing the tungsten and part of the silica, is evaporated to dryness twice with hydrochloric acid, taken up in weak HCI, boiled, filtered, and the residue washed with 1 : 10 nitric acid (water would cause it to pass through the paper). The insoluble matter from the fusion, which contains the iron, manganese, copper, and some of the silica, is dissolved in hot dilute nitric acid and evaporated to dryness. It is dissolved in weak HCl, and the silica is collected on the same filter that already holds the tungsten, washing as before with nitric acid.The combined precipitate is ignited and weighed as WO,+SiO,; then treated with 0.5 C.C. of sulphuric and 5 C.C. of hydrofluoric acid to volatilize the latter in the usual way. The iron and manganese are subsequently separated. I n the presence of chromium and aluminium, the filtrate from the tungsten should be precipitated with ammonia, the mixed oxides weighed together, dissolved in strong nitric acid and potassium chlorate, and the alumina thrown down alone by a small excess of ammonia. After adding nitric acid, the chromium in solution can be titrated with ferrous sulphate and permanganate, or reduced with peroxide and weighed as Cr,O,. Part of the aluminium will be found in the iron precipitate, and must be allowed for, Carbon may be conveniently estimated by the same process, for it is entirely converted into sodium carbonate, which can be decomposed with acid, absorbing the gas in barium hydrate.Corrections must be made for the several impurities, car- bonate, silica, and iron, in the sodium peroxide, for which reason a known amount must always be used. F. H. L. Estimation of Molybdenum. H. Brearley. (Chem. News, 1898, Ixxviii., 203.) -The author has investigated Chatard’s gravimetric process, which depends on the precipitation of sodium molybdate with lead acetate ; and also Schindler’s volumetric method of titrating an acidified solution of a molybdate with lead acetate, using tannin as an external indicator.To the former, various limitations were ascribed by Fresenius and by Chatard himself ; but the present experiments widen its range of usefulness and bring out the following points : It is not necessary to employ neutral solutions; some free acetic acid is advantageous, as it obviates any danger of precipitating lead if faint alkalinity has been overlooked. Two C.C. of 33 per cent. acid may safely be used when dealing with 0.1 gramme of molybdenum; but an excess tends to change the molybdate from a granular to a powdery nature, and * The author finds that copper resists the action uf sodium peroxide quite as well as nickel, while adventitious salts of the former metal are less troublesome iri the course of an analysis,THE ANALYST. 19 renders it liable to pass through the filter.This may be overcome by washing with a mixture of 1 C.C. of .lead acetate solution (7.896 grammes per litre) and 500 C.C. of water just acidified with acetic acid. It is not necessary to separate the precipitate from the prtper before ignition; they can be burnt together, wet or dry, in a muffle. It is advisable, however, to carbonize the paper at the lowest possible temperature, because extreme heating to remove refractory carbon is disallowed by the instability of the lead molybdate. The precipitate is not reduced nor appreciably altered in weight by ignition in presence of carbcn. It can be safely ignited at a moderate red heat; even at full redness, or the melting-point of sodium carbonate, it only loses about 1 per cent.in six hours. The chlorides and nitrates of sodium and ammonium do not affect the process; ammonium acetate, as made by neutralizing 0.880 ammonia with 33 per cent. acid, in large amounts simply involves a second filtration of the precipitate. It does not appear to retain alkaline salts, and prolonged washing is therefore unnecessary. If the ignited precipitate is dissolved in hydrochloric acid, neutralized with ammonia, treated with excess of acetic acid and a little more lead acetate, the purified molyb- date is never sensibly different in weight. Manganese, copper, cobalt, nickel, zinc, magnesium, and mercury (ic) exert no practical interference, and occasion no trouble beyond more careful washing or a reprecipitation of the ignited molybdate. Even the unpurified precipitate carries down with it but little of these metals; and their presence can generally be detected by a variation from the normal (creamy) colour of the product.Zinc molybdate is mostly dissolved by the usual excess of acetic acid; if only an opalescence remains, it may be neglected; if the liquid is distinctly cloudy, the free hydrochloric acid of the original molybdenum and zinc solution must be partly replaced by acetic. I n presence of mercury, the liquid must be warmed or ammonium acetate added. Uranium contaminates the molybdate of lead more seriously ; by one reprecipitation the error may be reduced to 0.5 per cent. ; but repeated operations are needed to separate the last traces. Schindler’s volumetric process is quicker and gives equally correct results with pure alkaline molybdates; but as the end of the titration is approached, the colour The method may be made more accurate by employing the tannin indicator as long as it is available (generally this is to within 1 per cent.of the truth), then filtering off a little of the hot liquid and testing it with lead acetate and sodium molybdate; more of the necessary reagent is added to the bulk, and the test is repeated with the same filter until the titration is complete, The influence of other metallic salts has not been investigated. The reaction between lead acetate and molybdenum is so delicate that in a solution faintly, but decidedly, acid with acetic acid, 1 part of molybdenum in 4 million produces a distinct cloudiness. Cobalt requires a second precipitation.eaction between the molybdate and the tannin becomes rather uncertain. F. H. L. The Analysis of Commercial Chrome Yellow. Willenz. (Bull. de Z’Ass. beZge., 1898, xii., 163-167.)-The author’s objection to Wittstein’s method of examining chrome yellow (Dingl. polyt. JOUT., ccx., 280) is that the lead chromate is not20 TEE ANALYST. completely decomposed by the digestion with sodium carbonate, and hence the residue cannot be correctly taken as barium sulphate. He has found, in fact, that the residue from pure lead chromate may amount to as much as 49 per cent. One gramme of the powdered material is digested with 100 C.C. of dilute hydrochloric acid (1.20) at a gentle heat, and the residue transferred to a filter and washed with hot water. The total calcium in the filtrate is precipitated as oxalate, the calcium present in the form of sulphate calculated from a determination of the sulphuric acid, and the calcium in the form of carbonate obtained by difference.The lead sulphate is determined by digesting the residue with 50 C.C. of a neutral or slightly alkaline solution of ammonium acetate (specific gravity, 1-04), filtering, and evaporating the filtrate to dryness with an excess of sulphuric acid. After the addition of 50 C.C. of water, the residue is boiled for about ten minutes with 25 C.C. of a solution of potassium hydroxide, containing 112 grammes of KOH per litre. This converts the lead chromate into potassium plumbite, which dissolves, leaving behind the barium sulphate and clay. A separate estimation of the amount of chromic acid is made by Bunsen’s iodometric method.C. A. M. The following method is recommended as giving satisfactory results. The Analysis of Incandescence Mantles. E. Hintz and W. Weber. (Zeit. anal. Chern., 1898, xxxvii., 94-111.)-The mantles which have come under the authors’ notice during the last three years have been composed almost without exception of thoria (96.42 to 99.26 per cent.) and ceria (0.49 to 2-02 per cent.), whilst the other rare earths, neodymia, lanthana, yttria, and zirconia, have only been present in minute quantities. Lime (0.1 to 1-05) and magnesia (trace to 0.21) were almost invariably present, and in some cases traces of silica. With the object of determining whether these minor constituents had any influence on the light-emitting properties of the mantles, one of the authors (Hintz) has made a series of photometric experiments, from which he has arrived at the following conclusions : 1.Zirconia, lanthana, and yttria added in small quantities up to 1 per cent. do not increase the illuminating capacity of pure thoria mantles, but, on the contrary, tend to lower it. A very small addition of neodymia is also without much effect, but when the amount reaches 1 per cent. there,is a slight increase in the quantity of light emitted. 2. The addition of neodymia, lanthana, or yttria (up to I per cent.) to mantles composed of thoria (99 per cent.) and ceria (I per cent.) does not increase their illuminating power. Similarly, an addition of from 0.2 to 1 per cent. of zirconia has no effect, but the influence of 0.1 per cent.is doubtful. 3. An addition of zirconia, neodymia, lanthana, or yttria (up to 1 per cent.} to thoria-ceria mantles containing 0.5 per cent. of lime is without effect. The authors have examined Knorre’s volumetric method of determining ceria (ANALYST, this vol., 191), and find that the results thus obtained are as reliable as those of the gravimetric method. For the volumetric estimation of ceria in theTHE ANALYST. 21 quantity in which it occurs in mantles they proceed as foIlows : 100 C.C. of the solution containing about 1 gramme of thoria and 0.1 gramme of ceria are acidified with from 5 to 7.5 C.C. of dilute sulphuric acid (1 : 6), diluted to 200 c.c., and the cerium compounds oxidized into the ceric state by adding three small successive portions of ammonium persulphate in the cold, and then boiling for one or two minutes after the first two additions, and finally for from ten to fifteen minutes after the final addition (about 3 grammes of persulphate are required to oxidize 0.2 to 0.3 gramme of cerium).At the conclusion of the boiling an additional 2 C.C. of the dilute sulphuric acid is added. When completely cold a dilute solution of hydrogen peroxide is run in, and the liquid rapidly titrated with potassium permanganate. The authors recommend the following simplified method for the analysis of unburnt mantles. A number of the stockings-not less than twelve-are weighed, and their upper and lower ends cut off, since the former are often dipped in a hardening solution, and the latter into a solution of a, ceriuin salt, in order to make the total percentage of ceria appear higher. The middle portions are weighed and completely extracted with water containing a few drops of nitric acid.The fabric remaining is ignited, the ash fused with potassium bisulphate, the melt dissolved in water containing hydrochloric acid, ammonia added, the precipitate dissolved in nitric acid, arid the solution added to the main solution, which is then made up to definite volume. 1. Neodymia is tested for spectroscopically in a portion of the concentrated solution. 2. An aliquot portion is treated with oxalic acid after removal of the free acid by evaporation. a. The precipitate is collected on a toughened filter, washed, and tested for neodymia, lanthana, and yttria as follows : The precipitate is washed into a beaker, heated with a concentrated solution of ainmonium oxalate, the liquid diluted, allowed to cool, and filtered after standing for a long time.As the authors have shown in a former communication (ANALYST, this vol., Sl), the residue left after extraction with ammonium oxalate contains a little thorium oxalate, so that even in the absence of neodymia, yttria, and lanthana, the percentage of ceria obtained will be higher than the truth, If, however, the amount calculated from the weight of the precipitate does not exceed that of the actual quantity of cerium present by more than 1 per cent., it may be at once concluded that neodymia, lanthana, and yttria are not present in sufficient quantity to affect the illuminating capacity.If, on the other hand, the excess is more than 1 per cent., a further examination is required. The weighed precipitate is dissolved by heating with sulphuric acid in a platinum crucible and the solution tested for these earths, b. The filtrate from n is evaporated to dryness, the residue gently ignited, dissolved in hydrochloric acid, the excess of acid removed by evaporation, and the zirconia tested for microchemically by evaporating a drop of the solution on the object-glass after the addition of a drop of a solution of potassium binoxalate. I n the presence of as little as 0.1 per cent. of zirconia characteristic crystals of potassium zirconium oxalate are to be observed. The presence of lime has also an influence on the result.22 THE ANALYST, 3.An aliquot portion of the solution after removal of the free acid is precipi- tated with oxalic acid, and the precipitate, consisting of the total rare earths excepting zirconia, ignited and weighed. Lime has an influence on the result, but for practical purposes the authors consider that it is not of great importance if, in a mantle containing, say, 98.4 per cent. of thoria, and 1.2 per cent. of ceria, 0.4 per cent. of lime is calculated with the thoria (= 98% per cent.). 4. The ceria is determined volumetrically in another aliquot part of the solution. The result deducted from that obtained in (3) gives the amount of thoria, provided that not more than negligible quantities of neodymia, lanthana, and yttria are present. C. A. M. Estimat,ion of Carbon i n Iron by Combustion.Rozycki. ( M o d . Scient., 1898, [4], xii., 636; through Chem. Zeit. Rep., 1898, 254.)-2*3 grammes of steel, or 0.25 gramme of ferrochrome, in fine powder, are mixed with 20 grammes of pure alumina, placed in a boat inside a combustion-tube 60 em. long, and ignited in a current of pure oxygen. The gas is led over red-hot copper oxide, and finally absorbed in baryta water. The baryta is decomposed with nitric acid in Wiborgh’s apparatus, and the carbon dioxide measured. The combustion occupies thirty-five minutes with steel, 1+ hours with ferrochrome. F. H. L. A Reaction of Metallic Sulphides soluble in Ammonium Sulphide. J. Ducommun. (Schzceix. ~ ~ o c h . Pharm., 1898, 434 ; through Deutsche Chem. Zeit., 1898, xiii., 346.)-When yellow ammonium sulphide is mixed with a small quantity of formaldehyde, the colour disappears, and after a short time a copious white preci- pitate is thrown down, which is entirely soluble in strong sulphuric acid. If the sulphide is first diluted till it is only faintly yellow, formaldehyde produces no precipitate, and the liquid remains perfectly clear.I n the presence of arsenious sulphide, the solution is bleached by the formalin, while sulphuric acid yields a white precipitate insoluble in excess. Antimony gives an orange-red precipitate on addition of acid; stannous or stannic sulphide, a, white; gold, a yellowish-white; platinum, a brownish-red ; the latter metal also prevents the previous decolorization. The precipitates are evidently some organic compound of the respective metals, for they turn black on ignition.I n all cases the liquids should be cold and highly dilute; and then the reaction is capable of detecting 2 milligrammes of arsenious acid, and somewhat more of either gold or platinurn. Arsenic acid only behaves in a similar fashion after it has be,en reduced by boiling the ammonium sulphide. The process may be employed in the course of ordinary qualihtive analysis to avoid the u6e of sulphuretted hydrogen. The solution containing various metals is neutralized with ammonia, treated with ammonium sulphide, and boiled to dissolve platinum and reduce arsenic compounds. One part of the filtrate is diluted and mixed with formaldehyde and acid. If a precipitate is produced, the remainder of the filtrate is analysed in the regular way ; but if no precipitate is formed, arsenic, antimony, and tin are absent, and the first sulphide precipitate, together with the inother liquor, is concentrated slightly, and boiled with strong hydrochloric acid in order to separate the mixture into a solution containing those metals whose sulphidesTHE ANALYST.23 are acid-soluble and a residue of the heavy metals, such as copper, etc., which yield insoluble sulphides ; these are then severally examined as may be necessary. The reaction shows that many sulphides, usually considered to be insoluble in ammonium sulphide, are really a trifle soluble therein-viz., copper, iron, lead, mercury. It should also be useful for detecting arsenic in pharmaceutical prepara- tions like bismuth subnitrate. F.H. L. Estimation of Sulphides, Sulphites, and Thioaulphates. W. Feld. (Chem. Industrie, ‘‘ 17J1898 ”; through Dezitsche Chem. Zeit., 1898, xiii., 322.)-The funda- mental reactions underlying the author’s processes are as follow : (1) Sulphides of the alkalis and alkaline earths, whether dissolved or suspended in water, are decom- posed by tt strong solution of magnesium chloride, forming sulphydrate and hydroxide, which are broken up on boiling in a, current of carbon dioxide into magnesium carbonate and sulphuretted hydrogen. The latter is absorbed in standard iodine. (2) Sulphites yield the theoretical amount of sulphurous acid on distillation with hydrochloric acid, and the gas is also absorbed by iodine. Thiosulphates cannot be estimated in this way, for on heating with hydrochloric acid they produce sulphuretted hydrogen and sulphurous acid, with the deposition of free sulphur.(3) But if a thiosulphate is treated with iodine, it is converted into tetrathionate, and the latter distilled with HC1 in presence of aluminium is reduced to H,S, which can be deter- mined in standard iodine as before. Any sulphite preRent at the same time is oxidized at once to sulphate, and takes no further part in the operation. (4) Thio- sulphates are decomposed by mercuric chloride, yielding mercuric sulphide and a sulphate. Sulphites are not attacked, so that they can be boiled with HCL, and the SO, absorbed as before. Excess of mercuric chloride is advantageous, and it may be employed in the solid state. An Erlenmeyer flask, holding 300 to 350 c.c., is fitted with a rubber cork having two holes.Through one is introduced a stoppered tube-funnel reaching to the bottom of the vessel; its upper opening can be closed with a cork bearing a, bent tube connected to a supply of pure carbon dioxide (conveniently a cylinder of liquid). Through the second hole of the main cork is passed a short tube joined to four Geissler’s potash bulbs, the ends of the several pieces of apparatus being made to touch within the rubber connecting tubes. The last set of bulbs is joined to a 10-litre aspirator to maintain and regulate the carrent of gas, and to measure roughly the volume passed. The first bulbs are empty, serving as water-condensers; the second are charged with a sufficiency (5 to 40 c.c.) of decinormal iodine to absorb all the gas evolved; the third contain some more (2 to 15 c.c.), diluted if necessary with water ; the fourth are filled with 5 or 10 C.C.of decinormal thiosulphate to catch m y volatilized iodine. To analyse a mixture of sulphide, sulphite, and thiosulphate, the sample in solution or fine powder mixed with water is brought into the flask, the cock on the funnel closed, and the whole apparatus tested for leaks. If satisfactory, the funnel tube is raised out of the liquid, and about 1 litre of CO, is passed to drive out air (were this precaution omitted, part of the H,S might be oxidized to free S, which, however, would be noticed in the empty bulbs). Twenty C.C. of a 25 per cent.24 THE ANALYST. solution of magnesium chloride (specific gravihy, 1.22) are run in through the funnel without admitting air, the tube is pushed down again to the bottom of the flask, the liquid is heated, and the gas turned on at such a speed that the aspirator is emptied in about forty-five minutes.The pozash bulbs are then rinsed out and titrated, 1 C.C. of +"Ti iodine being equal to 0*00895 gramme of B a s or to 0.0039 gramme of Na,S. The bulbs are charged once more, mercuric chloride and hydrochloric acid added to the contents of the flask, and the whole distilled again; the amount of iodine consumed represents the sulphite, 1 C.C. being equal to 0.0063 gramme of Na,SO,. A fresh portion of the original sample is titrated with & iodine till it turns blue (the quantity used need not be noted); the mixture is placed in the same flask, together with rolls of thin pure aluminium foil which partly project above the liquid, acid is added, the gas turned on, and finally the solution is gently warmed ; this gives the thiosulphate; 1 C.C.of iodine is equal to 0,00395 gramme of Na,S20,. I t is highly desirable to check the purity of the several reagents employed through- out the process, lest reducing gases be produced among them. F. H. L. Direct Conversion of Potassium Iodide and Bromide into Chloride. F. W. Kuster. (Zeits. anorg. Chenz., 1898, xviii., 77.)-Dry potassium iodide can be safely and quantitatively converted into chloride by ignition in a stream of chlorine at a moderate temperature, heating it (about 2-5 grammes) for half an hour in a, porcelain crucible over a luminous gas-flame about 2 cm.high, the top of which is kept 3 cm. from the base of the vessel. Even if the temperature be raised for a time till the crucible begins to glow, the loss is very minute (0.3 milligramme), and it is doubtful whether this is actually caused by volatilization of chloride. Dry potassium bromide cannot be decomposed in this manner; but if the sample be moistened, a similar reaction takes place more slowly, and by the following modification becomes equally available for analytical purposes. 2.5 grammes of the bromide are brought into an Erlenmeyer flask 7 cm. in height, together with 1 C.C. of water and 1 drop of 10 per cent. hydrochloric acid; and a current of chlorine is admitted through the porcelain tube of a Rose's crucible.The flask is placed on a sheet of asbestos, with a second sheet 2 cm. beneath, on which plays a small pilot gas-flame. The temperature is raised till the bromine evaporates quickly without boiling. After an hour or an hour and a half, one of the asbestos shields is removed and the water driven off ; then the heat is gradually increased until the remaining asbestos is visibly red. The whole operation is repeated once or twice to obtain constant weight ; but if a smaller quantity of bromide is taken in the first instance, the reaction is often complete the first time. The result may be most simply calculated by the use of the formula 9' %KBr = a + b- 9 where a= 267.59 ; b = - 267.59 ; g' the weight of the potassium chloride ; g that of the original bromide.The examples quoted by the author show yields of 100.00 and 100*01 per cent. when working on pure potassium iodide. A specimen of Kahlbaum's bromide gaveTHE ANALYST. 25 99.07 and 99.08 per cent. of KBr by the above method; 99-06 and 99.20 per cent. by ignition of the silver halide in chlorine (calculating from the potassium bromide itself); 99.16 and 99.10 per cent. by similar treatment (calculating from the silver compound}. Commercial iodide seldom contains any impurity except water ; bromide contains nothing except moisture and chloride. F. H. L. Volumetric Estimation of Combined Sulphuric Acid. M, Reuter. (Chenz. Zeit., 1898, xxii., 357.)-The author has submitted Andrews' method for the titration of sulphate solutions to a careful examination ; and he finds, provided the operation is carried out exactly in the following manner, that its accuracy, speed, and simplicity leave nothing to be desired.10 C.C. of the original solution, which should contain about 0.14 gramme of anhydrous sodium sulphate, are boiled with 150 C.C. of a solution of barium chromate prepared by dissolving 3 or 4 grammes of pure precipitated chromate in 1 litre of water by the aid of 30 C.C. of strong hydro- chloric acid. The acid is neutralized with powdered chalk, and the precipitate filtered off and washed; the filtrate is thoroughly cooled, acidified with 5 C.C. (not more) of strong HC1, treated with 20 C.C. of a 10 per cent. solution of potassium iodide, allowed to rest for five minutes in a covered vessel and an atmosphere of carbon dioxide (to give time for the complete reduction of the chromic acid, yet to prevent oxidation of the HI), then diluted to 1 or 14 litre, and finally titrated with decinormal thiosulphate.Three atoms of iodine correspond to one molecule of sulphuric anhydride, F. H. L. Method of Preparing an Exactly Neutral Ammonium Citrate Solution. A. D. Cook. (Jozir. Anzer. Chem. SOC., 1898, xx., 585-586.)-1t has been stated by several chemists that an exactly neutral ammonium citrate solution for agricultural analysis may be obtained by allowing the solution to stand after ammonia has been added to the citric acid and the proper dilution made. The author, however,-finds that this is only the case when the solution has a sufficient temperature to expel the excess of ammonia.By vigorous stirring sufficient heat for the purpose is caused by the chemical action, but if this is neglected the solution will be slightly alkaline. The method recommended for the preparation of the reagent is its follows: 740 grammes of commercial [citric acid are mixed with 1,900 C.C. of 10 per cent. ammonium hydroxide. After vigorously stirring the liquid until the acid has all dissolved, the solution is made up to 4,000 C.C. with water. I t is then again stirred and transferred to a large evaqorating dish, where it is allowed to stand over-night. Finally, it is transferred to the reagent bottle, brought to 20" C., and water added until the specific gravity is 1.09. C. A. M. Estimation of '' Available " Phosphoric Acid in Thomas Slag. J. Freund- lich. (Chem.Zeit., 1898, xxii., 974.)-Wagner has lately shown (ANALYST, 1897, xxii., 334) that in slags containing much silica, this substance may be prevented from contaminating the precipitate of ammonium magnesium phosphate, if the freshly26 THE ANALYST. prepared citrate extract be treated with magnesia mixture previously mixed with alkaline citrate solution. Many slags, however, also contain sulphide of iron and calcium ; and these bodies, being decomposed by the citric acid, yield sulphuretted hydrogen, which does not entirely escape, but, combining with the ammonia sfter- wards added, precipitates the iron once more, producing a blackish phosphate that becomes red on ignition. To avoid this error, a, second precipitation should be resorted to whenever the slags contain much sulphur ; and the ferrous sulphide in the first precipitate should be oxidized with nitric acid or aqua regia.F. H. L. Estimation of Perchlorate in Chili Saltpetre. 0. Foerster. (Chem. Zeit., 1898, xxii., 357.)-The ordinary method of reducing the chlorates and perchlorates in commercial sodium nitrate by heating the mass to a red heat has several disadvan- tages If the temperature be too low, they are not completely decomposed ; while on the other hand, chlorine is apt to be lost by volatilization of the sodium chloride. The author’s process is very exact, and does not demand the use of any particular degree of heat. 10 grammes of the sample are mixed with an equal weight of dry sodium carbonate (free from chlorine), and the whole is heated in a covered platinum or capacious porcelain crucible over a large flame for about ten minutes, till the mass is in tranquil fusion and no more bubbles of gas are given off.The melt does not creep up the walls of the vessel, and it is readily soluble. It is finally dissolved in excess of nitric acid, and the total chlorine is determined as usual. F. H. L. (Cf. Abstract, ANALYST, xix. 221.) Estimation of Perchlorate in Saltpetres. N. Blattner and J. Brasseur. (Chem. Zeit., 1898, xxii., 589.)-Five or ten grarnmes of the dried potassium or sodium nitrate are heated for fifteen minutes over a Btinsen flame with 8 or 15 grammes of calcium oxide, carbonate, or preferably hydroxide. The mass is dissolved in pure nitric acid, the total chlorine determined by any of the usual methods, and deducted from that already existing as chloride in the original sample.The process is more convenient than those in which alkali-metal carbonates are employed, because the mixture does not melt, and thus is more readily soluble, while there is no danger of loss by volatilization, etc. I n three different ship-loads of refined ” Chili saltpetre, supposed to contain at least 96 per cent. of sodium nitrate and less than 1 per cent. of sodium chloride, ‘the authors discovered from 0.12 to 1-01 per cent. of NaC1, and from 0-42 to 0-77 per cent. of NaClO, ; while a sample of potassium nitrate, ( ( pure for analysis,’’ contained 0.47 per cent. of perchlorate, but no chloride. F. H. L. (C’. ANALYST, xix., 221.) Microscopic Detection of Perchlorate in Chili Saltpetre.M. van Breuke- leveen. (Rec. trav. chim. des Pays-Bas, 1898; xvii., 94 ; through Chem. Zeit. Rep., 1898, 145.)-Behrens’ test for a perchlorate, which depends on the recognition under the microscope of the rhombic and almost insoluble crystals of rubidium perchlorate, can only be used in the examination of sodium nitrate when the impurity (calculatedTHE ANALYST. 27 as potassium perchlorate) amounts to at least 0.6 per cent. To detect smaller quantities (0.2 to 0.6 per cent.) 10 grammes of the sample are dissolved in 10 C.C. of hot water, diluted with 50 C.C. of 95 per cent. alcohol, raised to the boiling-point, and allowed to cool for one or two hours. The clear liquid is then poured off, evaporated to dryness on the water-bath, the residue taken up in as little water as possible, and Behrens’ test applied.If the rubidium salt is coloured with permanganate, only enough of the latter must be added to give the liquid a faint pink tint when it is placed on the microscope slide and held over a sheet of white paper ; or crystals of rubidium permanganate may be mistaken for those of the perchlorate. F. H. L. - _ _ _ _ _ _ _ _ ~ ~ A False Nitrous Acid Reaction in a Drinking Water. A. Bomer. (.&it. fiir Untersuch. der Nahr. uitd Geizussmittel, 1898, 401.)-The attention of the directors of a waterworks having been called to a strong nitrous acid reaction given by the water, the matter was referred to the author for report. The addition of zinc iodide and starch and sulphuric acid certainly produced a deep blue colour, On careful examination, however, the water was found to contain some suspended matter which proved to be manganic dioxide, the presence of which, in conjunction with the chlorides in the water and the added sulphuric acid, would be sufficient to account for the reaction. After separating the suspended matter from the water the reaction was not produced. A short time afterwards the author received from the same company €or examin- ation a piece of lead pipe containing a, brownish-black incrustation, which proved upon analysis to consist principally of oxides of manganese. H. H. B. S. The Advantage of using ‘( Normal Volumes ” in Analysis. M. Monhaupt. (Che7.lt. Zeit., 1898, xxii., 806.)-In the ordinary routine work of a laboratory, it is customary to weigh out such a quantity of the substance under examination that the final figures (weights, volumes, etc.) shall give at once the percentage of the ingredient sought ; the author pleads that the same device should be adopted when the sample is measured at the commencement of the test. For instance, in the potash trade, where determination of the proportion of potassium chloride in raw products, etc., is constantly required, the original (‘I normal ”) weight is always a multiple of 0.3056 gramme-the factor which converts K,PtCI, into KC1-and the final weight multiplied by 100 is the percentage desired. Similarly, when the analysis has to be conducted on a liquid, 30.56 C.C. (the ‘‘ normal volume ”) may advantageously be measured in a special pipette, and tedious calculation be avoided here also. F. H. L.