472 ABSTRACTS OF ,CHEMICAL PAPER,R INORGANIC ANALYSIS. Estimation of Aluminium Oxide and Total Aluminium in Steel. F. 0. Kichline. (J. Ind. and Eng. Chcm., 1915, 7, 806-807.)-1t is shown that alumina that has been heated to 1,000' C. for an hour, dissolves to the extent of only 3 per cent. when digested for an hour with dilute (1 : 1) hydrochloric acid, whilst alumina which has been heated to 2;OOOO C.is practicably insoluble. I t is held, therefore, that alumina, present in steel, which must have been subjected to a temperature of 1,600' C., is not likely to yield more than 1 or 2 per cent. of its weight to dilute hydrochloric acid, and a, 2 per cent. error in estimating the small quantity of alumina in steel is certainly negligible. That the alumina in steel is substantially insoluble has been shown directly by adding only just enough aluminium to deoxidise the steel, avoiding an excess.No aluminium was found in the solution of the steel in hydro- chloric acid. On these facts the following method of estimating alumina, in steel is based. The drillings (50 grms.) are dissolved in a mixture of 200 C.C. hydrochloric acid and 300 C.C. water.The insoluble matter is filtered off, washed with hot dilute (1 : 2) hydrochloric acid, and finally with hot water. The ashless filter and itsINORGANIC ANALYSIS 473 contents are incinerated, the residue fused first with 0.5 grm. sodium borate and, when in solution, with 5 grms. sodium carbonate. The alumina in the melt is then estimated in any convenient manner. Without the use of sodium borate, it is often impossible to decompose the alumina completely.I n the iron filtrate, aluminium originally present as metal is precipitated as phosphate by Blair’s modification of Wohler’s method. The precipitate is dissolved in nitric acid, any chromium oxidised by boiling with permanganate, and the aluminium precipitated from the chromium, copper, etc., by means of ammonia.This precipitate is dissolved in hydrochloric acid, the solution evaporated to separate silica, and in the filtrate aluminium is re-precipitated as phosphate. G. C. J. Application of Stock’s Reaction to the Volumetrie Estimation of Aluminium. T. V. Kovseharova. ( J . Russ. Plzys. Chem. Soc., 1915, 47, 616-624 ; through J. Ohm. Soc., 1915, 108, ii., 582-583.)-The author has examined Stock’a method for the volumetric estimation of aluminium (J.Chem. SOC., 1900, 78, ii., 247, 315). To a definite volume of potash alum solution are added a mixture in equal volumes of 25 per cent. potassium iodide and 6 per cent. potassium iodate solutions, and an excess of & sodium thiosulphate solution. The liquid is then heated to boiling, and the excess of thiosulphate titrated with iodine solution. A large number of estimations, carried out under different conditions, shows that trustworthy results are obtained when (1) the excess of sodium thio- sulphate solution is small, (2) the solution is as nearly neutral as possible, and (3) the heating on the water-bath is not continued for longer than twenty to thirty minutes.Arsenic Acid as an Alkalimetrie Standard.A. W. C. Menzies and F. N. McCarthy. (J. dmer. Chem. Soc., 1915, 37, 2021-2024.)-1t has been shown by Menzies and Trotter (ANALYST, 1912, 37, 580) that arsenic acid can be titrated with sodium hydroxide solution, using phenolphthalein as indicator, and that the end-point of the titration is quite sharp. The authors now give a method for pre- paring pure arsenious acid and for the conversion of the latter into arsenic acid.A 6 by I inch test-tube is constricted to about one-fourth its diameter at a point 2 inches from the closed end, and the end pocket thus formed is filled with com- mercial arsenious acid of good quality; the tube is then clamped horizontally with its pocket over, but not touching, a Bunsen flame. The arsenious acid collects as a sublimate in the other end of the tube; the sublimate is removed by cutting the tube at the constriction, dried by heating, and bottled while hot.To prepare 500 C.C. of & arsenic acid solution, a quantity of about 2.47 grms. of the sublimed arsenious aoid is weighed into a 75 C.C. conical flask, 5 C.C. of chloride-free concentrated nitric acid are added, then 5 C.C.of water, a suitable tube is placed in the neck of the flask to prevent loss by splashing, and the mixture is heated, gently at first, and then more strongly. When the arsenious acid has dissolved, 5 C.C. more of nitric acid are added through the above mentioned tube, the latter is removed, and the solution evaporated to dryness. The evaporation is acclerated by blowing a current of cotton-filtered, ammonia-free air into the flask.The dry residue is474 ABSTRACTS OF CHEMICAL PAPERS then dissolved in water, the solution evaporated to dryness, water is again added, and the evaporation repeated. These operations are necessary in order to remove the last traces of nitric acid. The final residue, consisting of arsenic acid, is dis- solved in water and diluted to the required weight or volume of solution.An approximately FG alkali solution, when standardised against pure bensoic acid, WBS found to have a factor of 1.0040; against standard hydrochloric acid, 1.0037 to 1.0039 ; against arsenic acid, 1.0036. w. P. s. Titration of Nitrates with Ferrous Sulphate. F. C. Bowman and W. Scott. (J. Ind. and Eng. Chem., 1915,7,766-769.)-The method depends on titration with a concentrated solution of ferrous sulphate in strong sulphuric acid solution, the acid strength of which must not fall below 75 per cent.at the end of the titration. Under these conditions, provided the temperature is not allowed to exceed GO" c., nitric acid is not reduced to NO, but only to N20,. The ferrous solution is made by dissolving 176 grms. crystallised ferrous sulphate in 400 C.C.water, stirring the solution into a cooled mixture of 250 C.C. water and 250 C.C. sulphuric acid, cooling and diluting to 1,000 C.C. One C.C. of this solution contains 0.8 C.C. water, and is approximately equivalent to 0.02 grm. HNO,. Its exact titre is best determined by titration with nitric acid, made from pure acid and standardised by titration with alkali.To 100 C.C. of sulphuric acid a measured quantity (10 c.c.) of nitric acid is added by means of a pipette the contents of which to the mark are known. The pipette is used to stir the liquid and its contents are delivered near to the bottom of the vessel containing the acid. The pipette is rinsed by sucking up sulphuric acid into it and letting this flow back.The ferrous solution is then added from a burette, with constant agitation of the liquid, until the appearance of a delicate pinkish-brown colour. From the con- sumption of ferrous solution, 0-2 C.C. is deducted, this being the excess required to give a pronounced coloration. In conducting sn analysis, as much of the sample as will require about 30 C.C. of ferrous solution is dissolved in such a quantity of water that the final acid con- centration will not fall below 75 per cent., and added to 100 C.C.of sulphuric acid and titrated as described, deducting 0.2 C.C. from the apparent consumption of ferrous solution. The method is not suited for the estimation of traces of nitrate, and gives only approximate results when applied to commercial nitrate of soda, the impurities in which interfere.The method has been used successfully for estimating nitric acid in fuming sulphuric acid of American manufacture, which appears always to contain 2 per cent. and often 3.5 per cent. of nitric acid. I t is also useful for mixtures of sulphuric and nitric acids, such as may have to be assayed in explosives works. In such mixtures nitric acid can be estimated with an error not exceeding 1 part in 300, Chlorates and chlorides interfere, but nitrites do not.G. C . J. Assay of Platinum. F. Mylius and A. Mazzwcchelli. (Chem News, 1915, 112, 88-91, 104-107, 125-126, 134-135, 144-146, 155-156 ; from Xeitsch. anal. Chem., 1914, 89, 1-38.)-The authors ignore the rarer constituents of commercial platinum, but deal with the detection and estimation of all the ordinary ones inINORGANIC ANALYSIS 475 great detail.Fourteen qualitative reactions of each of the six platinum metals in 0.1 per cent. solution are tabulated, the method of carrying out colorimetric estima- tions with solutions of the chlorides in presence of hydrogen chloride is described, and a simple process for the analysis by precipitation of dissolved platinum alloys is recommended. The behaviour of ruthenium chloride towards ammonium chloride is explained by means of new experiments, and the existence of iridium mercaptide proved. Methods of separating the platinum metals from one another have been tested and improved, and a, special method is proposed and described in detail for the quantitative analysis of technical platinum.Finally, for the detection of impurities in high-grade platinum a, method is described as a supplement to that recommended by Finkener and tested by Mylius and Forster for the purification of the metal. G. C. J. Estimation of Traces of Silver by the Cyanimetric Method. G. Rebikre. (Bull. SOC. Chznz., 1915, 17, 306-309.)--In DenigBs’ method of estimating silver by means of potassium cyanide in’ammoniacal solution the end-point of the reaction is shown by the use of potassium iodide as indicator. As the opalescence due to silver iodide is not readily perceptible, the author detects its formation by directing 6 beam of light through the flask.One hundred C.C. of the silver solution are shaken with 10 C.C. of standard cyanide solution containing 10 C.C.of i% potassium cyanide solu- tion and 20 C.C. of ammonia solution in 100 c.c., and the excess of cyanide titrated with i& silver‘nitrate solution, with a, drop of potassium iodide solution as indi- cator, until a bluish opalescence is rendered visible by the first excess of 0.05 C.C. of the silver solution. C. A. M. Effect of Grinding Soil on its Reaction as Determined by Veitch’s Method.P. E. Brown and H. W. Johnson. (J. Iyzd. and Eng. Chem., 1915, 7, 776-777.)-1t is shown that, when acid soils are ground before being tested by Veitch’s method, the acidity is reduced and frequently the reaction becomes basic, owing to the basic reaction of finely ground silicates. As the weathering of coarse granular silicates is much too slow to remedy acid conditions in the soil, soils should not be ground previous to testing their reaction by Veitch’s method.G. C. J. Probable Error of Sampling in Soil Surveys. G. W. Robinson and W. E. Lloyd. (J. Agric. Sci., 1915, 7, 144-153.)-The usual method of sampling for survey purposes is to select a field uniform in itself and representative of the type; borings are taken at various points, and the samples mixed for analysis, representing the top soil and subsoil respectively. The total probable error (P) of a, single boring is a function of the laboratory error (pJ and the field error ( p J , due to the normal variation from point to point of the Geld.Each of these has a different value for the various items. The experiments recorded illustrate the operation of these errors ( A ) in the case of a field not sufficiently uniform for survey purposes; (23) in that of a suitable field, a complete mechanical analysis and determinations of hygroscopic moisture, organic matter, and phosphoric acid being made separately on each boring.I n the mechanical analysis the value for fine gravel is subject to the476 ABSTRACTS OF CHEMICAL PAPERS largest errors of both classes, but this item is of relatively small importance.Excluding this, the experiments showed an average laboratory error of +2*5 per cent., and a probable field error of round about 210 per cent. for the mechanical determinations, and +, 13.4 per cent. for the phosphoric acid in the case of field A . For the more uniform field B, the field errors in mechanical analyses were small, and in the estimation of phosphoric acid were k7.3 per cent.For survey work gene- rally, & maximum field error in a single boring of rtl0 per cent. may be taken as a fair basis for the chemical analyses, and k 5 per cent. for the mechanical. The total probable error can then be reduced by increasing the number of borings and the number of determinations.The total probable error is represented by the expression P= J*22, and if borings are made and analysed separately, this would be divided by &. On the other hand, if IZ borings are mixed and analysed as a single sample, only the field error is divided by J< while the laboratory error remains. Thus, when the field error is comparatively large, there is little advantage in analysing the borings separately.In a suitable field ( B ) the errors may be reduced sufficiently for general survey purposes by taking six borings and making duplicate determinations on the mixed sample. The expression for the probable -2F5 error then becomes +, 2/( j a y+($y= -L 2.7 per cent. for a mechanical analysis, and 2 2/(z)2+ (%r = * 4.4 per cent.for a, chemical analysis. JJ J6 Calculating thence the probabilities, it would appear that an accuracy of 5 per cent. may be expected with a probability of 4 to 1 in the case of a mechanical analysis, but in a chemical anaIysis the same degree of probability only covers an error of k 8-3 per cent. J. F. B. Effect of Changes in the Viscosity of Water on the Results of Mechanical Analyses conducted at Varying Temperatures.G. W. Robinson. ( J . Agric. Sci., 1915, 7, 142-143.)-1n the mechanical analysis of soils by practical sedimentation discordant results will be obtained if the experiments are performed at widely divergent temperatures owing to the change in the viscosity of the water. According to Thorpe and Rodger's formula, the increase in viscosity over the range of 10°.C., corresponding to a fall in temperature from 15' to 5" C., amounts to 33 per cent., in comparison with which the changes in the densities of the solid and liquid are quite negligible. This increase in viscosity affects the limiting diameter of the particles remaining in suspension in the ratio of the square root of the viscosity, so that the limiting diameter of the particles in suspension is 15 per cent. greater at 5' C. than it is at 15" C., and if there is a large proportion of particles at or about this limiting diameter the effect on the sedimentation fractions may be very con- siderable. This eflect has been shown in the separation of samples of mixtures of fine sand and silt made at different temperatures. Taking the fine sand fraction at 6" C. as equal to 100, the amount collected at 11" C. was 105.7 and at 16" C. 108.1. These analyses should therefore always be conducted at a constant temperature, preferably 12" to 14' C. J. F. B.