Oct., 1921 THE JOURNAL OF INDUSTRIAL AND ENGINEERING CHEMISTRY 939 CONCLUSIONS Modifications in bleaching methods give promise of greater The chemical characteristics of soda and sulfate pulps result,s than modifying cooking methods. indicate that they are a very pure form of wood cellulose and Modifications in which the bleaching operation was divided capable of high yields of white fibrous and resistant material. into two steps, with washing between steps, cut the bleach The sulfate process is much more efficient than the soda requirement in two. process in yielding a bleachable pulp from coniferous wood. Pulps of better quality, both from physical and chemical The coloring matter in pulps is of the nature of a dye and considerations, are obtained by cooking the wood as little can be removed without materially reducing yields. Most as possible in isolating the fibers and by accomplishing as of the action in cooking to reduce bleach consumption is to much of the burden of purification as possible in the bleaching dissolve and degrade the cellulose. and washing operations. The Determination of Vanadium and Chromium in Ferrovanadium by Electrometric Titration' By G. L. Kelley, J. A. Wiley, R. T. Bohn and W. e. Wright MIDVALESTEEL & ORDNANCE C0.p NICETOWNPLANT, PHILADELPHIA, PENNSYLVANtd The object of this paper is to describe a method for the When the vanadyl sulfate is titrated at 80" C. with perman- determination of vanadium in ferrovanadium not subject ganate in a similar acid concentration, the change of poten- to interference by chromium, which is so often present. Kel- tial is about 60 mv. Under these conditions the color of ley and Conant2 described the electrometric titration of permanganate is not visible until about 0.20 to 0.25 cc. more vanadium following oxidation with ammonium persulfate of the permanganate solution has been added. The poorer and silver nitrate, but the method did not provide against quality of the work done with permanganate may be due ts the possible presence of chromium. Kelley and the collab- the incompleteness of the reaction between the permanganic orators3 above named described a method for the selective acid and vanadyl sulfate, and the results are, doubtless, oxidation of vanadium in steel in the presence of chromium, affected by the exposure of the hot solution to air during using nitric acid as an oxidizing agent. At that time, how- titration. ever, we were not prepared to recommend the application NITRIC ACID OXIDATION-The solution of vanadyl sulfate, of our procedure to the determination of vanadium in ferro- standardized as above, was used to check further the degree vanadium. Since then its application to the analysis of of oxidation effected upon vanadyl salts by nitric acid. 13 this alloy has been studied. our earlier paper on the selective oxidation of vanadyl salts PRELIMINARYEXPERIMENTAL WORK by nitric acid in the presence of chromic salts, it was sug- gested that the vanadium be considered approximately 99 DETERMINATION OF VANADIUM IN AMMONIUM VANADATE- per cent oxidized. Our more recent work leads to the be- A large volume of solution was prepared from ammonium lief that the degree of oxidation is more nearly 99.5 per cent. vanadate described by the maker as C. P. This was analyzed With the object of simulating conditions which would obtain by two methods. In the first, the vanadium was determined if the work were done upon ferrovanadium, solutions were by titrating the solution with ferrous sulfate and dichromate, prepared containing 0.3 g. of pure iron, 0.1273 g. of vanadium taking as the end-point the point of greatest change in the as ammonium vanadate, 25 cc. of sulfuric acid (sp. gr. 1.58), oxidation-reduction potential. The potassium dichromate 40 cc. of nitric acid (sp. gr. 1.40), and water enough to make solution was made from a C. P. salt which had been re- the total volume 200 cc. The iron was first dissolved in the crystallized and fused. It was also compared through the sulfuric acid and water in the presence of the ammonium ferrous sulfate with permanganate which had been standard- ized against sodium oxalate. The average difference be- vanadate, thus reducing the latter to vanadyl sulfate. The tween these standardizations was less than one part in one mixture was boiled for 1 hr., at such a rate that the volume was 100 cc. at the end of the period. It was then cooled to thousand. In the second method, 100 cc. of the ammonium 5" and titrated electrometrically with ferrous sulfate and vanadate solution were placed in a flask, with an equal vol- C. potassium dichromate. Out of twenty-four determinations ume of water and 5 cc. of sulfuric acid (sp. gr. 1.58); and treated with sulfur dioxide for 20 min. at the boiling temper- made, the value found for percentage oxidation was 99.3 in four cases, 99.5 in eleven, 99.6 in six, and 99.7 in three. ature. The excess of sulfur dioxide was removed by passing The average was 99.5 per cent oxidation, with a maximum purified carbon dioxide through the still boiling solution for an additional 20 min. Two hundred cc. of a boiling water variation of 0.2 per cent above and below. solution containing 50 cc. of sulfuric acid (sp. gr. 1.58) were We have previously shown' that chromium is not oxidized next added, and the mixture was titrated hot with 0.05 N under these conditions. We have made a further investigation of the effect of con- permanganate using the potentiometric end-point. Eight determinations by the first method gave 0.1273 and 0.1274 ditions upon the oxidation of vanadium by nitric acid, but inasmuch as our results were largely negative, they need not g. of vanadium in 100 cc. of solution, the average result being nearer 0.1273. The solutions titrated with perman- be described in detail. Oxidations conducted in flasks at ganate after sulfur dioxide reduction did not agree so well. the boiling temperature, with air passed through for 6hrs., The results ranged from 0.1269 to 0.1275, averaging 0.1272. did not show consistently higher oxidation than solutions The condition most favorable to titration with ferrous boiled 1 hr. in beakers covered with watch glasses. When sulfate is an acid concentration of about 50 cc. of sulfuric air was excluded, the results were slightly lower. acid (sp. gr. 1.58) in a volume of 350 cc. at a temperature METHODFOR DETERMININGCHROMIUM AND VANADIUMIN of 5" @. Under these circumstances the change in potential FERROVANADIUM for 0.05 cc. of the ferrous sulfate solution (23 g. ferrous am- Dissolve 3 g. of ferrovanadium in 75 cc. of nitric acid (sp. monium sulfate in one liter) is about 50 mv. at the end-point. gr. 1.13). When solution is nearly complete, add 10 cc. of hydrochloric acid (sp. gr. 1.20). When the amount of 1 Received April 13. 1921. * J. Am. Chem. Soc., 88 (Isle), 349. silicon is large, it may be convenient to add a few drops of *Tars JOURNAL, 11 (1919), 632. 1 LOG. ci). 940 THE JOURNAL OF INDUSTRIAL AND ENGINEERING CHEMISTRY Vol. 13, No. 10 hydrofluoric acid to bring about solution. Next add 50 cc. sponding to chromium but expressed in terms of vanadium. of sulfuric acid (sp. gr. 1.58) and evaporate until fumes ap- Dividing this by 2.943 gives the percentage of chromium. pear, to remove nitric and hydrochloric acids, and to com- The use of the factor 2.943 may be avoided if 2.883 g. of plete the decomposition of vanadium carbides. The in- potassium dichromate are used to prepare the solution. In soluble residue after this treatment is generally small and this case each cc. corresponds to 1 per cent of vanadium consists chiefly of aluminium oxide. Ordinarily no loss of when the sample titrated contains 0.3 g. of the ferro-alloy. vanadium occurs if it is disregarded, but it may be dissolved APPLICATIONOF METHOD in water after fusion with sodium peroxide. The alkaline The application of this method to the analysis of two solution so obtained should be boiled for at least 15 min. samples of ferrovanadium known to contain chromium gave to remove hydrogen peroxide. The solution may then be the following results: acidified with a slight excess of sulfuric acid and added to the Chromium and Vanadium main filtrate. This solution is then cooled and made up to -as Vanadium-- -Vanadium- SAMPLE Per cent Average Per cent Average a volume of 1000 cc. One hundred cc. portions of this solution. A 41.29, 41.32, 41.34 41.32 33.05,33.13, 33.09 33.09 corresponding to 0.3 g., are convenient quantities for subse- B 48.29, 48.36 48.32 43.30,43.36, 43.40 43.35 quent work. By calculation from the averages, Sample A contained DETERMINATION OF VANADIUM AND CHROMIUM-TOa 2.80 per cent of chromium, and Sample B contained 1.61 100-cc. portion add 25 cc. of sulfuric acid (sp. gr. 1.58) and per cent. water enough to make the volume 300 cc. Heat the solution To check the accuracy of this method of determining to boiling and add 20 cc. or more of a 10 per cent solution of chromium in ferrovanadium, a procedure which separated ammonium persulfate and 10 cc. of a 0.25 per cent solution of most of the vanadium was devised. It had the advantage silver nitrate. Boil the solution at least 10 min. to oxidize of permitting work with a much larger amount of chromium the vanadium and decompose the excess of ammonium per- in the presence of a greatly diminished percentage of va- sulfate.