INDUSTRIAL A N D ENGINEERTNG C H E M I S T R Y
316
solution. After the addition of phosphoric acid the titration was performed as previously described. It was not found possible to determine the small amount of vanadium in the tungstic acid precipitat,e by reduction titration with diphenylamine as indicator, in the presence of phosphotungstic acid. The intense color of the vanadyl tungstate masked the end point. It was subsequently found that small amounts of vanadium could be determined colorimetrically in the presence of 0.2 to 0.5 gram of tungsten. Diphenylamine was added after solution of the precipitate in alkali and acidifying with phosphoric and sulfuric acids. This possibility was not studied in detail. Determination of Chromium in Steels and in Ferrovanadium
CHROMIUM-VANADIUM STEEL, OR FERROVANADIUM-The familiar method of oxidation by ammonium persulfate in the presence of silver nitrate was employed. The details of the United States Steel Chemists' modification as furnished by Lundell, Hoffman, and Bright," were followed. After completion of the oxidation and precipitation of the silver as chloride, it was found necessary to remove the silver chloride by filtration through asbestos. I n the presence of silver chloride there was no definite end point. Some of the blue substance separated on the surface of the silver chloride. After cooling the filtrate and adding phosphoric acid, titration with diphenylamine as indicator gave the amount of ferrous sulfate which is equivalent to both chromium and vanadium. The amount equivalent to the vanadium, as determined separately, was deducted for the calculation of the per cent of chromium. This method, being indirect, is obviously not satisfactory for the determination of small amounts of chromium in the presence of large quantities of vanadium, as in ferrovanadium. CHROMIUM-VANADIUM-TUNGSTEN STEEL--After SOlUtiOn Of the steel and removal of the tungstic acid, the excess of hydrochloric and nitric acids was expelled by heating with sulfuric acid. The method described in the previous section was then followed.
Vol. 17, No. 3
range of 0.4 per cent,. One analysis of a large sample gave a value close to that of the certificate. Vanadium in Ores
Inasmuch as ferric iron, quinquivalent arsenic, and hexavalent uranium are without influence upon the accuracy of the determination of vanadium with diphenylamine as indicator, the method should be applicable to the examination of certain vanadium ores. A specimen of carnotite ore was examined.12 From 2 to 4 grams of ore were decomposed by treatment with aqua regia. The residue was brought into solution with the aid of hydrofluoric and sulfuric acids. After heating with sulfuric acid until nitrates and chlorides were completely removed, oxidation was completed by treatment with potassium permanganate, as in steel analysis. Determinations were made by reduction with ferrous sulfate, with diphenylamine as indicator, and also by oxidation with permanganate after separation and reduction of t,he vanadium. PERCENT VANADIUM FOUND Reduction method 1.36 1.23
Oxidation method
1.38 1.38
1.39 1.41
12 Supplied through the courtesy of I ,. W. McCay, who found 1.04 per cent of UaOliin the ore.
An Individual Laboratory Hood' By George W. Muhleman HAMLINE UNIVERSITY,ST. PAUL, MINX.
VERY laboratory where a course in qualitative chemical E analysis is given has the problem of adequate vent,ilation. If the atmosphere becomes intolerable with noxious fumes
it is an expensive proposition to supply fresh, warm air during cold weather. The apparatus described below has been devised in this laboratory to remove noxious fumes. R A f unnel-s h a pe d hood of sheet metal painted black, 16.5 cm. (6.5 inches) in diTable 111-Application of Diphenylamine Method to Steels a n d ameter at the base and Ferro- Alloys Chromium Weight Vanadium 11.4 cm. (4.5 inches) found BUREAU OF STANDARDS of sample found high, has a perforated Per cent SAMPLE Grams Per cent No, 30 B . Chromiumtube solderedonto the 1.045 Vanadium Steel 2 0.210 top, which can be 2 0.205 2 0.204 attached to a suction Certificate value: 2 O.l.96 1.033 V . , 0.208% average 3 0.183 pump.. The hood has 0.215% recoma spring-like handle, 1.036 mended 4 0.204 C r . . .1.030% 4 0.199 through which two Av. 0.201 1.038 holes are bored so that No, 50 Chromium-vanadium-Tungsten Steel 1 0.746 3.67 the hood can be con1 0.720 3.61 Certificate value: 1 0.750 nected to a ring-stand V . . . 0.756% 2 0.783 a n d a d j u s t e d to H O S e + o Cr.. .3.61% 2 0.760 3.64 Av. 0.752 any desired height. 5 ~ 2 ~ Weight When hydrogen of sample Gram sulfide is b u b b l e d p p ~ ~ No. 61 Ferrovanadium 0.5055 31.33 0.3609 0.46 (High Carbon) through a solution, or 0.7190 0.48 0,3736 31.34 w h e n a solution is 31.04 Provisional certificate: 0.3374 30.93 0.2461 V . . . 31.15% being evaporated, this hood can be lowered over the vessel 31.23 0.2410 Cr . . . 0.5S% and all fumes are pumped directly into the drain. This hood 30.97 0.2482 Si . . . 7 . 7 % 31.25 0.7243 can be used in any laboratory. 30.96 0,3057 31.06 0.4055 Students in this laboratory have individual hydrogen Av. 0 . 4 7 Av. 31.12 sulfide generators consisting of a 250-cc. flask, a dropping Aliquot portion of 3.2034 31.16 funnel, and a delivery tube. This method of preparing hyThe results for chromium and vanadium are satisfactory drogen sulfide has been found bot,h convenient and economiin the case of steels. The vanadium values for the small cal, as there is never the problem of repairing a large genterrovanadium samples are distributed over a rather broad erator, and no unnecessary waste of ferrous sulfide. ,
11 THISJOURNAL,
16, 1067 (1923).
1
Received January 26, 1925.
