256
T H E J O U R N A L OF I N D U S T R I 1 4 L .AND E,lrGI,YEERtSG CHEJIISTRY.
different solubility relations compared with the normal phosphomolybdate, with respect to the usual washing solutions used in determining phosphorus. (3) Conditions are given for quantitatively precipitating vanadic acid when in solution alone, or accompanied b y a variety of other element;, b y means of ammonium phosphomolybdate. (4) In order t o determine quantitatively the vanadic acid so precipitated, ( a ) the possibility of freeing it from the accompanying molybdic acid was investigated. ( b ) Conditions for reducing i t without reducing the associated molybdic acid were developed. (c) A method for reducing it b y hydrogen, and other peroxides and titrating i t against permanganate was elaborated. ( 5 ) The method (c) was applied to a variety of steels, t o iron ores, manganese ores, and t o synthetic mixtures, in all-of which the vanadium was determined with great accuracy. BUREAU OF STANDARDS,
WASHINGTON. D. C.
A NEW METHOD FOR THE DETERMINATION OF VANADIUM; AN EXPLANATION. BY J. R. CAIN AND
D. J. DEMOREST.
Received January 25, 1912.
The discrepancy in results obtained b y us when using manganese dioxide, as mentioned in the paper on “ A New Method for the Determination of Vanadium,” page 249, 1 e d . u ~t o seek the cause. We exchanged samples of manganese dioxide and each found t h a t the other’s reagent behaved as stated in our respective papers. However, it was noted by Mr. Cain t h a t Mr. Demorest’s dioxide, which oxidized differentially, was much coarser than the manganese dioxide which the former had used, and which oxidized both the lower oxides of vanadium and iron. Upon grinding the coarse manganese dioxide very fine he found that it oxidized both iron and vanadium oxides as his own preparation had done. On the other hand, Mr. Demorest succeeded in separating a coarse portion from the manganese dioxide used b y Mr. Cain which oxidized differentially. Thus, the discrepancy is evidently due t o a difference, in the two cases, of the velocities of the reactions : (I) V,O, MnO, = MnO V,O, ( 2 ) FeO MnO, = Fe,O, MnO
+ +
+
+
Mr. Demorest’s reagent had a degree of fineness such t h a t in the brief period of treatment the velocity of reaction ( I ) was inappreciable and reaction ( 2 ) was completed; whereas with material of the fineness used b y Mr. Cain both reactions went to completion. The securing of such different results merely by changing the size of the grain of the reacting solid seems a matter worthy of further investigation.
April,
1912
THE RAPID DETERMINATION OF VANADIUM IN STEEL. Ry FRANK GARRATT. Received Dec. 20, 1911.
The writer has for some time used the following modification of Johnson’s method‘ for determining vanadium in steel. Johnson’s procedure is adhered t o in all respects, except that the oxidation of the chromium and vanadium in hot, dilute sulfuric acid with potassium permanganate is omitted. With this omission the method is extremely simple and, briefly, is as follows: Dissolve 2 grams of steel in about 5 0 ’cc. of dilute sulfuric acid; when solution is complete, oxidize the iron, and tungsten if present, b y adding about 5 cc, of concentrated nitric acid to the hot solution. Boil until nitrous fumes are expelled, or in the case of tungsten steels, until the separated tungstic acid is of a pure yellow color. Dilute the solution t o about 150 cc., filter if tungstic acid is present, and cool to room temperature. Dilute t o about 350 cc. in a suitable beaker, add a little ferrous sulfate solution, and obtain the old rose3hade with permanganate. Add the potassium ferricyanide indicator, and titrate a t once with standard ferrous ammonium sulfate solution for the vanadium value. As pointed out b y Johnson, blanks must be run on steels of similar composition, and consistent endpoints adhered to in the titrations. As outlined above, the determination, even in the case of tungsten steels, may be completed in 2 0 minutes. If tungsten is absent the filtration may, of course, be omitted, thus shortening the operation. If chromium is not t o be determined, there is no reason, of course, for its oxidation. As a matter of fact, without this oxidation the blanks seem t o be smaller and more uniform. Carbonaceous matter does not seem t o interfere in the subsequent titration. The writer thinks that Johnson’s scheme of adding the ferricyanide indicator t o the solution t o be titrated, gives the most practical method yet offered for the technical determination of vanadium in steel. Blair’s method,* with proper precautions, leaves nothing t o be desired in the way of accuracy, but it consumes too much time and care for a busy works laboratory. Cain’s methods is, of course, much shorter but i t does not offer the advantages in regard t o simplicity and rapidity that Johnson’s method possesses. Blair’s and Cain’s methods may well be considered desirable for standardizations and umpire determinations, but Johnson’s method seems to be the one for routine work. If the procedure described herewith is adopted, the determination of vanadium is much simplified, and takes its place with the rapid methods for determining carbon, phosphorus. manganese, etc. Certainly the laboratory doing routine work on vanadium steels need not worry about its determination. The following table gives some results obtained b y this rapid modification. Some of the steels contained no chromium, while others varied from 0.906.00 per cent. The presence of chromium offers 1
“Chemical Analysis of Special Steels, etc
J. A m . Chem. Soc , SO, 1229. 3 THIS JOURNAL, 3, 476. 2
,”
p. 8.
