ANALYTICAL CHEMISTRY. Analytical Chemistry. Electrv-thermic Methods of Aizalyllsis ard Synthesis. By E. MULDER and F. C. E. von EMBDEN.~ PO%many experiments such as the combustion of carbon or sulphur the reduction of carbon dioxide by carbon &c. a simpler arrangement than that previously described by the authors may be adopted. If it is desired to burn carbon in oxygen for instance a large test- tube or a flask is partially filled with the gas over the mercurial trough the volume being marked by means of a caoutchouc ring. Into this vessel is introduced a copper wire carrying at its upper end a small dish made of clay through the bottom of which it passes. To the extremity of the wire is attached one end of a fine platinum wire which is wound round a fragment of charcoal and connected by its other end to a copper wire passing through the dish and dipping into the mercury in the vessel.The copper wire carrying the dish is insu-lated by a glass tube bent into the form of an inverted siphon with very unequal limbs the longer limb reaching above the level of the mercury in the tube or flask while the shorter projects above the sur-face of the mercury in the trough. This tube becomes partly filled with mercury in the act of introducing it with its contained copper wire into the vessel of gas. The apparatus being thus arranged one pole of a battery (two Grove’s elelvents are quite suficient) is dipped into the mercury in the trough and the other into that in the glass tube where- upon the platinum wire becomes red-hot and the charcoal is kindled.Another method applicable however to fewer experiments consists in the use of a float which may be made of clay. To burn sulphur in oxygen for example a copper wire passes through the float being secured underneath and carrying above a small dish of copper or clay on which is a fragment of sulphur fused to a platinum wire one end of which passes through a hole in the dish and i8 fastened beneath the other end being connected with an insulated copper wire passing through the dish and float and secured to bAh. The vesscl being partly filled with oxygen and the height marked with a caoutchouc ring the float is introdnced and rises to the surface of the mercury. One pole of the battery is connected with the mercury in the trough the other with the insulated wire; the platinum wire then becomes red-hot and the sulphur burns quietly.J. R. * Beitschrift fur Chemie [2] vii 1. ABSTRACTS OF CHEMICAL PAPERS. A Method of QzicLm5fntiveAnalysis cmcl Synthesis. By E. MULDER." THEprinciple of thianiethod will be made clear by an example. A?anlysis of gaseous Hydmpz Cldode 6y meaws of iyon A graduated glass tube closed at one end is partially filled with the gas over the mercurial trough and the volnine read off in the usual manner. Two copper wires one of which is insulated by glass are then introduced into the tube. One of these mires is coiled into a flat spiral at top ; the other carries at its extremity a kind of brush formed of a number of ihort pieces of iron wire of different lengths secured to it by means of platinum wire.One pole of a battery of three Grove's elements being connected with the mercuryin the trough and the other with the insu-lated copper wire the apparatus is adjusted with the hand so that the ends of the iron wires are brought into contact with the copper coil whereupon the iron begins to glow and ferrous chloride is formed. When the volume of the gas ceases to contract the wires are removed and the volumes of theresidual hydrogen is read off. It is :obvious that one of the wires may be of platinum passing through the top of the tube the other which need not then be insu-lated passing up through the mercury as before. This principle modified to suit particular c:tses is applicable to the analysis of compound gases and vapours such as hydrogen chloride hydrogen sulphide or water-vapour by means of iron copper &c.; or of mixtures of gases such as oxygen and nitrogen by means of copper (method of analysing air).It is applicable further to the combination of gases as hydrogen and oxygen and of solid elements as iron carbon sulphur &c. It may also be employed to effect the combustion of carbon iron and other solids in nitrogen protoxide nitrogen dioxide &c. ; or of gases by means of partially oxidized iron or copper wire lead-chromate and other solid compounds of oxygen ; or of vapours such am alcohol-vapour (method of organic analysis). Lastly it is appli- cable to experiments on the dissociation of gases and vapours such as ammonia or water-vapour by platinum palladium &c.This method of experimenting is extremely well suited for lectures the apparatus being simple and t'he manipulation easy J. R. On some Sources of Error in Tolumetrk Analysis. By R.R.TAT LOCK.? THE object of the author is to point out cert'ain sources of error in volumetric analysis and to indicate how they niay be avoided. Reference is made to the contradictory statements of various experi- ++ Zeitxhrift fur Chemic [2] rii 2. t Cliern. News xxiii 13. ANALYTICAL CHEDIISTRY 157 mentalists respecting the change of volume that takes place on mixing saline solutions with water. From the fact that the specific gravity of a mixture of a saline liquid and water is greater than its calculated mean and from direct experiments it is inferred that contraction does as a rule take place on admixture of a saline liquid with watsr.Strong solutions were found to contract proportionately far more thail weak ones. Two sources of error are specially mentioned-the one arising from this contraction and the other from tlie fact that vessels do not deliver in a given time corresponding volumes of water and saline solution but rather less of t'he latter the exact amount depending to some extent upon the sp. gr. of the solution. The first named source of error may be obviated (1) by using as weak soluticns as possible and (2) by mixing the saline liquids thoroughly with the water before making quite up to the required bulk.The error caused by the adhesion of it saline liquid to the delivering vessel may be obviated by graduating it in terms of the particular solution to be employed. A. T. On the P.recipitation of Slrzall Quantities of Phosplzo& Acid by nzeuns of Ammonium Xolybdate together with a few Renzarks on the Yellow Prec+itate containii2g Silico-molybdic Acid. By E. R I cH TE R s.* AMMONIUM molybdate deservedly enjoys the reputation of being an extremely delicate reagent for phosphoric acid. Its sensitiveness depends however upon well-defined conditions which must be strictly complied with if small quantities of phosphoric acid have to be deter- mined. Among these is the absence of free hyd.rochloric acid in anything like large quantities whilst nitric and snlphuric acids do not interfere with the accurate precipitation of phosphoric acid within the usual limits of quantitative analysis.It is otherwise however in the case of earthy minerals &c. the solution of which usually contains extremely minute traces of phos- phoric acid together with much free acid and a large amount of salts (nitrates and sulphates). A large excess of ammonium molybdate has to be employed in order to counteract the solvent power of distilled water on the free acid as well as on the salts. The sulphates and nitrates of the light metals especially of the metals forming the strongest bases are found to retard the separation of the precipitate and require therefore the largest amount of ammonium molybdate. A 5 per cent.solution of the ammonium sulphate acidulated with &lute nitric acid on the other hand acts rather favourably. Nitrates in general appear to assist the precipitation. Ammonium nitrate was especially observed to accelerate the formation of the yellow precipitate Dingl. po'lyt J cicix 183. 158 ABSTRACTS OF CHEMICAL PAPERS. in a most extraordinary manner and from very dilute solutions the precipitation being accomplished also by a much smaller quantity of ammonium mol ybdat e. Standard solutions containing respectively- (I) *002grm. and (11) -010 grni. of phosphoric acid per litre ;also solutions. (I11and IV) containing the same amounts of phosphoric acid dissolved however in ammonium nitrate (100 grms. per litre) were prepared.10 C.C. of solutioiis I and 11,to which 0.3 C.C. of a solution of ammonium molybdate had been added remained perfectly clear on standing for several hours in a waim place. Solution 111 gave a precipitate on standing at the ordinary temperature for twelve hours; solution IT,after stancling for 30 minutzs only. The pre- cipitation was complete after 20 hours and the further addition of several cubic centimetres of ammonium lzlolybdate to the clear filtrate produced no further precipitate even on heating for 24 hours. On warming solution 111 a precipitate was produced after the lapse of one hour and on adding a further quantity of ammonium molybdsic (about 2 C.C. for every 10 C.C. of solution) the sensitiveness of the reaction in the presence of the ammonium nitrate became practically unbounded.The extent to which ammonium nitrate counteracts the solubility of the phospho-molybdate precipitate in solutions of the sulphates and nitrates of the alkalis and alkaline earths as far as they are soluble (concentration 1in 10 or if less soluble saturated solutions) was next ascertained and it was found that ammonium nitrate assists the pre- cipitation in a like ratio. Solutions containing much nitric acid required only about one-third the amount of the reagent in the presence of ammonium nitrate. Richters proposes to conduct the determination of very small quan-tities of phosphoric acid in the presence of large quantities of nitrates and sulphates as follows :-The acid solution is diluted with water so as to leave about 1grm.of the salt in 10 c.c. or if much ammonium sulphate be present 1grm. in 20 C.C. The solution is rendered slightly ammoniacal and then once inore acid (nitric acid). If IG sufficient amount of ammonium nitrate be not already formed in this manner an equal volume of a 20 per cent. solution of this salt is added and the solution heated to 50" C. after the ammonii-un molybdate has been added. On adding aminonin to n tlioro.ilghlyacid (nitric) solution a certain amount of ammonium nitrate is formed (which may be readily estimated if the strength of the ammonia solution be known) and should be taken into account in diluting the solution to the above strength. The separation of the yellow precipitate is both rapid and complete in fact instantaneous from solutions which contain only _-o,A of the weight of the original salts.AXALYTICAL CHEMISTRY. Richters proposes to employ a slightly acidified 15 per cent. solu-tion of ammonium nitrate in the place of ammonium molybdate for washing the yellow precipitate or else a nitrate solution mixed with a few cubic centimetres of the ammonium molybdate. The precipitate obtained from the phosphate solutions containing much ammonium nitrate is distinguished by a somewhat brighter yellow colour. Richter s remarks lastly on the yellow precipitate produced by ammonium molybdate from solutions containing silicic acid which is but slowly soluble in cold dilute ammonia with separation of flakes of silicic hydrate and not unfrequently accompanies the magnesia11 precipitate to which it gives its flaky appearance.w. v. Estimation of Xu@ltur in Cast IYO~.By W. H. ELLIOTT.:* THIS method depends on the evolution of the sulphur as sulphuretted hydrogen the absorption of the latter in solution of pure soda (pre- pared from sodium) and the determination of the sulphuretted hydrogen in the acidified soda-solution by means of standard solution of iodine. w. v. Estimation of P?tosp?~o~us is5 ovde Pig-I~on,Steel nzzcl iVa7leccble Iron. By F. KESSLER.? THI~ method is based upon the precipitation of the iron in the state of ferrous chloride by potassium ferrocysliiide FeCl + K4FeCy6= Fe"K2PeCy6+ 2KC1 and the separation of the phosphoric acid from the filtrate in the form of ammonio-magnesic phosphate.As the pro- cess involves filtration from a bulky precipitate-an operation known to every chemist as being among the most tedious-the author proposes to collect only the first haIf of the filtrate for precipitation with magnesia mixture. Assuming an iron to contain 1per cent. of phos-phorus in order to obtain a precipitate of magnesium pyroplzosphate amounting to ,100 grni. 2.793 grms. of crude iron mould hare to be operated upon; or as only half the bulk of the filtrate is to be employed the quantity of the metal would have to be doubled. This quantity of metal (5.6 grms.) after solution in acid requires no less than 42 grms. of crystallised potassium ferrocyanide. The ensuing pre- cipitate weighing at least 34 grms.exclusively of chemically combined water it became necessary to make a correction for bulk. 11grms. of soft iron wire were dissolved in hydrochloric acid and the solution diluted to 500 C.C. 84 grms. of crystallised potassic ferrocyanide were dissolved in water and the solution likewise made up to 500 C.C. The specific 8 Chemical News xxiii 61. -f Chemical News xxiii 76. 160 ABSTRACTS OF CHEMICAL PAPERS. gravity of the iron solution was found to be 1.055 that of the ferro-cyanide solution 1.093. 250 C.C. of each solution were mixed and the bulk of the mixed solutions was then found to be equal to 505 C.C. The filtered liquid had a specific gravity of 1.033 hence the bulk of the liquid was calculated as follows :-250 (1.055 + 1.093) -34 = 503 grms.503 and 50s --=18 C.C. 1.033 In order therefore to work only with 250 c.c.-one-half the filtrate- the liquid containing the precipitate has t'o be first madeup to 518 C.C. This quantity may be varied according to the purity of the metal from 517.5 to 518.5 C.C. Previous to dissolving the iron in acid it should be suitably commi- nuted; crude pig-iron for instance should be broken up in a steel mortar and passed through a sieve the meshes of which are 0.5 mm. apart. 5.6 grms. of the metal are then treated in a corered porcelain vessel with 60 C.C. of nitric acid sp. gr. 1.2;the solution is evaporated to dryness ; and the residue strongly ignited (best in a muffle) to bright redness first in the porcelain vessel next in a platinum crucible in order to oxidize the carbon.It is then dissolved in 35 C.C. of hydro- chloric acid sp. gr. 1.19 with the aid of a gentle heat. A residue of silica is left. The acid solution so obtained is washed into a flask without being previously filtered and diluted to about 200 C.C. A current of sulphuretted hydrogen is next passed in order to reduce the ferric to ferrous salt a method of reduction which Kessler prefers to the reduction by means of an alkaline sulphite. 200 C.C. of a solution of potassium ferrocyanide (strength 210 grms. of the crystallised salt per litre) &re next added and the bulk of the liquid made up to exactly 518 C.C. The precipitate is filtered OR. Prom 20-30 C.C. of the first portion of the filtrate usually pass through turbid andmay be rejected.250 C.C. of the clear filtrate are collected in a graduated flask and precipitated in the usual way by adding in a beaker 10 C.C. of magnesia mixture (strength 200 grms. ofmagnesium sulphate per litre). Kessler observes that the precipitate is always covered with a greyish flocculent substance which he removes by throwing the precipitate and the body just referred to on a small filter and washing with ammonia of sp. gr. 0.98. He next dissolves the precipitate which adheres to the sides of the beaker and also the portion contained on the filter in nitric acid of sp. gr. 1.035 when a bluish coloured insoluble cyanogen-compound is left behind. The phosphate is reprecipitated by means of ammonia collected on a small filter and washed with ammonia of sp.gr. 98,until on testing no more chlorine is detected. It is then dricd ignited and weighed as magne- ANALYTICAL CHEMISTRS. lG1 sium pyrophosphaie *lo0grms. of which salt correspond to 1per cent. (or more correctly to 09975 per cent.) of phosphorus. The author states that he found the method correct in every respect and suitable for all practical purposes and that he prefers it to the molybdic acid method for the estimation of phosphorus in crude pig-iron steel and malleable iron. w. v. Estimation of Zinc in Galvanized Iron. By THOMAS T.P. BRUCE WARREN.* THEzinc in galvanized iron exists in two states; firstly part of the zinc forms an alloy with the iron; and secondly to this alloy a greater or lesser quantity of zinc adheres mechanically.Only the part of zinc forming the alloy is necessary for the protection of the iron. This combined zinc cannot be removed from t,he iron by mercury but is nevertheless capable of uniting with a definite proportion of that metal '7 parts of this combined zinc taking up 11parts of mercury. On heat-ing the iron the mercury is again volatilised. On the other hand all the uncombined zinc can be removed by means of mercury. Let then a piece of galvanized iron be taken weighed cleaned with dilute sul- phuric acid and ipmersed for from 4 to 8 hours in mercury ; it will be found that part of the zinc has been removed part has remained on the wire together with the mercury absorbed. The piece is next taken out of the mercury well rubbed with chamois leather and again weighed after which it is heated iU EL non-oxidizing flame and the weight once more taken.The difference between the first and third weighings will be the uncombined zinc while the difference between the second and third weighings when multiplied by 7 and divided by 11,gives the combined zinc. This process moreover reveals all imperfections in the zinc coating since no mercury adheres firmly to such places. A. D. On a Mode of distinguiskimg the Deposit from Reimh's Pyocess from ST. CLAIRGRAY.? Salts of Mercuyy. By JAMES THE coated slip of copper is rubbed with a flat piece of pure gold. If the deposit on the copper contaius mercury the gold becomes marked with a clear white shining crust which is removable by nit,ric acid.C. H. 0. a Pllil. Mag. [4] xli 132. -f-Chem. News xxxiii 73. ABSTRACTS OF CHEMICAL PAPERS. Estimatiol of U7-ei-r by means of Soditcnz Hypobromite. By G. HUFNER.* HYPOCHLORITES, as is well known decompose ammonia compounds with evolution of nitrogen and Woh1er.f. based upon this reaction R method for determining the amount of ammonia in guano. It consists in measuring the nitrogen which a weighed quantity of guano yields when treated with a solution of bleaching powder the amount of ammonia being calculated €i*om the volume of nitrogen which is given Off. Urea is ached upon in a similar manner it is converted by the hypochlorous acid into free nitrogen water and carbonic anhydride 1 grm. of urea corresponding to 370 C.C.of nitrogen (at 0" C.and 760 m.m. pressure). E. W. Davy$ described in 1854 a method-afterwards somewhat modified by Leconte-by which he effected (although imperfectly) the decomposition of the urea and the collection and measurement of the nitrogen in a graduated cylinder over a saturated solution of com-mon salt. W. Knop proposed to employ instead of sodium hypochlorite a. solution of barium or sodium hypobromite an oxidizing agent which is at once more effective and more stable and a solution of which is readily prepared when required. The preparation of sodium or barium hypobromite is described by Rnop fj as follows 600 grms. of barium hydrate are placed in two litres of water and are shaken up with 100 C.C.of bromine. On adding a solution of 300 grms. of barium hydrate in one litre of water (prepared by dissolving the hydrate iii warm water) the bromine disappears and a golden-yellow solution is obtained which probably contains barium bromate and bromide as well as bromite and hypobromite. Sodium hypobromite is obtained by dissolving 100 grms. of sodium hydrate in 250 C.C. of water and leaving the solution to cool before adding 25 C.C. of bromine. 50 C.C. of this solution diluted with 200 C.C. of water suffice to liberate 130 to 150 C.C. of nitrogen from a solution of sal-ammonaic. The instrument devised by Knop-known under the name of agonteter-renders it possible to determine urea rapidly and readily and to complete within 15 to 20 minutes several determinations with sufficient accuracy.Hiifner now proposes to modify Knop's method so as to employ * J. pr. Chern. [2] iii 1. f-Prakt. Uebuiigen in der Chem. Analyse Boettiiigen 1853. 5 Phil. Mag. [4] iii 385. § Freseilius Zeiisch. f Aaalyt. Cliein ix 2 p. 225 ANALYTICAL CHEMISTRY. 163 a gentle heat in order to complete the re-action securing at the same time the advantage of not having to mix the urea solution and the oxidizing agent before the gas can be collected On heating the hypo- bromite solution oxygen is however evolved as well and the mixed gases (nitrogen and oxygen) are therefore collected in a gradnated cylinder. A urea solution is placed in the lower part of a mixing apparatus shut off from the part containing the concentrated hypo- bromite solution by means of a wide-bore glass stop-cock.A glass cup from 4 to 5 c.m. in depth is fitted to iis neck by means of a caoutchouc ring over the open end of the mixing vessel which reaches somewhat above it and delivers the evolved gases into the mouth of the inverted measuring cylinder which is about 30 c.m. long and 2 c.m. wide. The lower part of the mixing apparatus below the glass stop-cock has a diameter of 1.5 c.m. and holds about 10-11 C.C. of urea solution. The bore of the glass stop-cock should not be less than 7-8 mm. The upper portion of the mixing vessel is large enough to hold about 100C.C. of sodium hypobromite diluted with its own bulk of distilled water. The glass cup is filled with a saturated solution of common salt over which the measuring cylinder filled with distilled water is inverted and fitted into its position.On opening the glass stop-cock the specifically heavier hypobromite solution mixes rapidly with the urea solution and a brisk evolution of gas ensues. The Pecomposition is assisted towards the end by plunging the lower part of the mixing vessel into hot water. A small quantity of oxygen has to be deter- mined in the usual way by transferring the gases over mercury and absorption with pyrogallic acid. The published experiments approximate closely to the theoretical percentage of nitrogen in urea. The author adds in conclusion some speculations on the composition and constitutional formulze of other nitrogenous bodies such as hippuric acid ethylamine aniline coniiine nicotine asparagine uric acid creatine and others for which we must refer to the original paper.w. v. Detection of Alcohol in Chloroform and Chloral Hydrate. By HAGER. HAGER has carefully examined* the method for the detection of ethylic alcohol described by (A. Lieben Ann. Oh. Pharm. Xzqy. viii 2) based on the formation of iodoform and finds it extremely delicate and capable of detecting of alcohol in a liquid after about one day’s standing. He uses the following reagents 1. A solution of potassium iodide in 5 to 6 times its weight of water supersaturated with iodine ; * Pharm. J. Trans. [S] i 683. ABSTRACTS OF CHEMICAL PAPERS. 2. A ten per cent. solution of potassium hydrate. To detect alcohol in cl~lorofo~w2,2 vols.of the latter are shaken up with 5 to 10 vols. of water of about 50" C. ; the liquid is then poured on a filter previously saturated with water; to the filtrate are added 5 or 6 drops of thc potash 'solution and the whole is heated to about 50" C. ;the iodidc solution is then added drop by drop with gentle agitation until the colour of the liquid remains brown and finally it is cayefully decolorised by the addition of potassium hydrate and set aside to deposit. After 12 to 24 hours the sediment is examincd 1i11derthe microscope and t'lie iodoform crystals recognised by their star-shaped form. The presence of alcohol or rather of chloral alcoholate in c7doi.d kydrate may be detected in a similar manner. Schering (ibid.) calls attention to other distinctions between chloral hydrate and alcoholate :-the former when warmed with twice its vol.of water dissolves but the latter melts without solution and solidifies again on cooling. Siilphuric acid remains colourless when warmed with the hydrate whereas it turns brown with the alcoholate. No reaction or only a very slight one ensues on warming the hydrate with nitric acid sp. gr. 1.2; the alcoholate is violently attacked and nitrous €umes are evolved in abundance. H. E. A. Eznmindion of F1ou.r. By W. DANCKWOETT.* THEauthor has endeavoured to ascertain approximately the amount of wheat-flour present in what was declared and taxed as rye-flour. The amount of residue (gluten) left after washing out the starch and soluble matter from different mixtures of wheat and rye-flour was determined ; mixing the flour with weli washed wheat-bran appears to facilitate the drying of the residue.The bag in which the sample is put the flour and bran employed are all thoroughly dried in the water- oven; as is also the gluten left by the washing. 10 grms. rye-flour mixed with 1grm. wheat-bran placed in a bag of silk bolting-cloth of a certain fineness and washed with distilled water until the water was no longer milky gave after subtracting the weight of the bag and bran a residue of 0*5-0.8 per cent. ; pure wheat-flour similarly treated gave 7.0-8*0 per cent. residue ; mixtures of 3 p. rye- with 1p. wheat-flour 1.0to 2.0 per cent. ; mixtures of equal weights of rye and wheat- flour gave 3.0to 3.5 per cent.residue. These numbers were the mean of several experiments. The suspected flour similarly treated gave in seven experiments a residue varying from 1.0-2.2 per cent. This would be given by a mixture of 70-75 per cent. rye-flour with 25-30 per cent. whea,t-flour. * Arch. Pharm. [2] xx 47. ANALYTICAL CHIZMTSTRY. Microscopical examination of mixtures of the two flours gave very doubtful results. W. H. D. Analysis of 17lilk.* By J. A. WANKLYN. THE“British Medical Journal” reports the following result of an analysis of the contents of a tin of Newnham’s condensed milk. Water ............ 19.0 Casein ............ 10.0 Ash .............. 2.0 Fat ............. Milk-sugar ........ 69.0 Cane-sugar ........There appeared to be about as much fat as casein. From this analysis it follows that one pound of the condensed milk contains the solid constituents of from three to four pounds of Gesh milk. In the course of an examination of milk undertaken for the “Milk Journal,” the observation was made that there is a source of inaccu-racy in the ordinary methods of examining milk hitherto quite unsus- pected. It mas found that the exact molecular condition of the casein influenced the specific gravity of the milk in other words that samples of milk of the same strength varied in specific gravity according to the molecular condition of the casein. The followmg examples are given to show how this may cause a want of correspondence between the specific gravity of milk and the amount of its solid contents.The speaimens of milk had been kept in corked bottles for four days. Per cent. of SP. gr. solids dried Per cent. at 60 9. at 212”F of mh. Sample A .... 1*0004 11.34 0.94 B... 0.9960 10.48 0.75 ,7 79 C.. .. 1.0184 8.92 0.66 To be of any value at all the specific gravity must be taken while the milk is very fresh for when milk is kept for two or three days even in a closed vessel the density falls in a very remarkable manner. It is therefore proposed in judging of the strength of milk to adhere to the method of evaporating to dryness in the water-bath and weigh- ing the residue. J. B. * Pharm. Journ.‘Trans. [3] I,605. VOL. XXIV. 0