October, 1923
INDUSTRIAL A N D ENGINEERING CHEMISTRY
1069
METHOD11-(For the Accurate Determination of Vanadium) This method is not as troublesome as might appear a t Dissolve 2.000 grams of the sample contained in a 200-cc. Erlen- first sight, and is quite rapid if such facilities as an electromeyer flask, in 30 cc. of dilute sulfuric acid (10 per cent by volume). If the steel contains less than 0.1 per cent vanadium, lyzing apparatus and cylinders of sulfur dioxide and carbon dioxide are a t hand. When the mercury has become satuse a larger sample and correspondingly more acid. When action is complete, dilute to 100 cc. with boiling water, heat t o urated with iron and chromium, a fair degree of purification boiling, and proceed with a sodium bicarbonate precipitation can be attained in a few minutes by shaking in a separatory as in the determination of manganese described above. funnel with concentrated hydrochloric acid. 40 Place the paper and sodium bicarbonate precipitate in the The following results reported for renewal No. 306 (recomoriginal flask, add 20 cc. of nitric acid (specific gravity, 1.42), shake until the paper is broken up, and then add 5 cc. of sulfuric mended value = 0.215 per cent vanadium) indicate the acid (specific gravity, 1.84). Heat over a free flame until fumes performance of the different methods: colorimetric methodz8 of sulfuric acid are given off, cool, and then add more nitric (0.18, 0.21), 0.19; Johnson’s method,410.22,420.20; Garratt’s acid and repeat the heating if the organic matter has not been destroyed. Finally, cool, wash down the sides of the flask, modification of Johnson’s method, 43 0.22; Kelley’s electroand evaporate again until fumes of sulfuric acid appear and until metric titration method, 0.22, 0.22; Cain and Hostetter’s it is certain that all the nitric acid has been expelled. Cool, method,44 (0.26, 0.20), 0.20; Campagne’s method,33 0.18, dilute to 40 cc.,36 neutralize the solution with ammonia, and 0.19, 0.20; Blair’s method45(final procedure as in Campagne’s then add 1 per cent by volume of sulfuric acid in excess. Transfer the weakly acid solution to the electrolyzing apparatus, method), 0.22; Method I, 0.21, 0.21, 0.18, 0.20, 0.21, 0.20; rinsing the flask with small portions of water, and keeping the Method 11,0.22,0.21, (0.16,0.21), 0.20. total volume of the solution down to 70 cc. The electrolysis I n careful analyses an accuracy to *0.01 per cent can be may he performed with a mercury cathode in (1) the special modified separatory funnel described and pictured by Cain3; easily attained with steels containing 1 per cent of vanadium and iO.02 per cent with steels containing 2 per cent. In and also by Blair;37 (2) in a small beaker with sealed in platinum wire as described by Smith,38 or (3) in a n ordinary beaker with routine analyses an accuracy to hO.02 per cent in low vanathe cathode lead enclosed in a glass tube extending into the dium steel and * 0.04 for 1 per cent, and k0.06 for 2 per cent mercury. I n any case the cathode lead should be imbedded vanadium steels is to be expected. in about 200 grams of mercury, and the solution electrolyzed (preferably with a stirring arrangement) using a current of 4 0 For more complete purification, see J. H . Hildebrand, J. A m . Chem. 5 to 6 amperes a t 6 to 7 volts. Continue the electrolysis until S O C . , 31, 933 (1909). iron is removed as indicated by a ferricyanide test on a small 4‘ L O C . czt. drop of the electrolyte. This will ordinarily require 15 to 20 4 1 With preliminary removal of copper. minutes if the electrolyte is stirred. When iron is absent, re4 3 Garratt, THISJOURNAL, 4, 256 (1912). move the electrolyte and wash the mercury two or three times 44 Cain and Hostetter, I b z d . , 4, 250 (1912). with 25 to 30 cc. of water while the current is continued. If 41’ Blair, 106. c i t . , p. 209. the electrolyte is not absolutely free from iron, the electrolysis must be continued until it is. Arsenic is the only element to be feared. The small amounts of arsenic (up to 0.02 per cent) Wearing Qualities of Shoe Leathers usually present in steel may be ignored except in the most acWearers of shoes need definite information on the wearing curate work. Ip precise work or where large amounts of arsenic quality of leather to enable them to buy shoes economically ; are present, the properly acidified electrolyte must be treated with hydrogen sulfide, the solution filtered, and every trace tanners need such knowledge to enable them to make high-grade leather and t o use their raw material to the best advantage and of hydrogen sulfide expelled from the filtrate before the prea t the lowest cost. To supply this information, the Bureau of liminary oxidation with permanganate as above. If all hydrogen Chemistry in 1919 began a series of experiments a t various sulfide is not expelled, this oxidation gives rise to sulfur which later reacts with sulfur dioxide to yield oxidizable products army training camps, which furnish the basis for a bulletin recently issued by the Department of Agriculture. which cause high and erratic values for vanadium. Add 2 to It was evident from these experiments that shoe uppers made 3 cc. of dilute sulfuric acid ( I : I ) , heat to 70” to 80’ C., and add permanganate solution until a strong pink color appears. from the better portions of cow-grain leathers of good quality will outwear two or more soles. Fiber soles of the kinds used Pass suliur dioxide into the boiling solution for a few minutes, were not suitable for the conditions of wear, owing principally to or until ihe vanadium is reduced to the quadrivalent condition, the fact that as soon as the soles had worn down through the and then a rapid stream of carbon dioxide free from oxygen until stitches they frequently ripped and broke off. Imperfections, the solution is free from sulfur dioxide, as shown by bubbling such as ripping, bulging, chipping, and breaking, were numerous the stream through a feebly acidified dilute solution of perin the fiber soles. manganate. The direct use of a solution of sulfur dioxide or of Disregarding the possibility of misfitting, a full double sole any alkali sulfite is inadmissible unless these have been freshly prepared, for after a lapse of time they contain other oxidizable and double shank of heavv leather seems to be responsible for the wasteful excessive toe wear. as such a shoe bends Gut little and bodies than sulfurous acid or sulfite. Sulfur dioxide is most the weight of the body is concentrated a t the extreme end of conveniently used from a cylinder of the liquefied gas, or it may the sole, instead of being distributed over a greater area a t the be obtained as wanted by heating a flask containing a solution of sulfur dioxide, or of a sulfite to which sulfuric acid is a d d e ~ l . 3 ~ ball. The serviceability of various tannages, based on a standard Sulfur dioxide must, of course, be entirely removed before the succeeding titration. Cool the solution to 60” to 80’ C. and thickness of 9 irons, was found to be as follows: oak bark, 78 days; hemlock bark, 79 days; chestnut wood extract, 80 days; titrate with 0.03 N potassium permanganate solution which has been standardized against sodium oxalate. Repeat the belting, 85.5 days; waxed chrome, 102 days; unwaxed chrome, 126 days; and fiber soles, 122 days. Among the outstanding inreduction and the titration until concordant results are obtained. The titration should be corrected by a blank determination dications of the experiments are the superior pliability of retanned-chrome and chrome-tanned upper leathers, certain ob(usually amounting to about 0.10 cc.) on a solution of like volume and acidity. The final solution may be evaporated to small jectionable features of fiber soles and the long wear of those that did not develop such features, the increased serviceability of rolled volume and, qualitatively tested for vanadium with hydrogen sole leathers, and the strikingly longer wear of chrome-tanned peroxide in acid solution, or with hydrogen sulfide in ammoniacal sole leathers, especially of the unwaxed chrome-tanned leather. solution. 36 Tuugstic acid retains vanadium (abont 0 01 mg. for each per cent of tungsten in t h e steel [Kelley, Wiley, Bohn, and Wright, THISJOURNAL, 11, 633 (1919)j. Consequently, if any appreciable amount is present at this stage, the solution must be filtered and the washed residue dissolved in a n excess of ammonia. Vanadium is then separated from tungsten by the adclition of 1 g. of alum, precipitation by a slight excess of ammonia, filtration and washing. The precipitate is dissolved in hot dilute hydrochloric acid, heated with 1 t o 2 cc. of sulfuric acid till fumes appear, and the solution added t o t h e original filtrate. 87 L O L . a t . , p. 200. 88 ”Electro-analysis,” 5th ed ,p. 62, P.Blakiston’s Son & Co. 89 W P. Hillebrand, U.S. Geol. Surv., Bull. 700, 186.
SUGGESTIONS TO AUTHORS
The booklet “Suggestions to Authors,” which we recently announced was in preparation, is now ready for distribution, and copies will be mailed to those who will send a request therefor to the editor’s office. Cooperation of authors in following these suggestions will be greatly appreciated in the editorial office, and by lessening ambiguity and thus making possible more prompt publication will help to bring about better satisfaction to all concerned.
