ANALYTICAL EDITION
448
The hydrous titanium oxide so obtained is dehydrated to form pure titanium dioxide by igniting at about 900” C.
A spectroscopic analysis (by E. Posnjak, Geophysical Laboratory, Carnegie Institution, Washington, D. C.) of titanium oxide prepared as above showed the presence of 0.001 t o 0.01 per cent of sodium as the only impurity. This last is probably due to contamination during the handling of the calcined titanium dioxide, as no special care was observed in order to obtain a spectroscopically pure product. ACKNOWLEDQMENT Acknowledgment is due to J. L. Turner, Director of Research, Titanium Pigment Company, Inc., for the suggestion on which this paper is based.
Vol. 6 , No. 6
LITERATURE CITED (1) Hickson, E. F.,et al., PTOC.Am. SOC.Testing Materials, 24, I, 451 (1924). (2) Hixson, A. W., and Plechner, W. W., IND.ENG.CHEW.,25, 262 (1933). (3) Jarmus, J. M., and Willets, W. R., Paper Trade J., 98, 41-3 (1934). (4) Jones, C.,Trans. Am.Inst. Mining Engrs., 17, 414 (1889). (5) Scott, W. W.,“Standard Methods of Chemical Analysis,” 4th ed., Vol. 1, p. 5444, D.Van Nostrand Co., N. Y., 1925. and Shimer, E. B., Orig. Com. 8th Intern. Congr. (6) Shimer, P.W., Appl. Chem., I, 445 (1912). (7) Thornton, W.M., Jr., “Titanium,” Chemical Catalog Co., N. Y., 1927. RECEIVED June 12, 1934.
Inclusion of Rarer Metals in Elementary Qualitative Analysis 11. Inclusion of Titanium and Vanadium in Group I11 LYMANE. PORTER, University of Arkansas, Fayetteville, Ark.
T
HE detection of tungsten and molybdenum in the presence of the common ions of groups I and I1 has been described in a previous paper (3). The detection of the only other two rarer metals to be considered in this series is outlined in the present paper. Solutions of titanium salts may be prepared by fusion of titanium dioxide with an excess of sodium bisulfate, followed by solution in water and acid. To remove the sulfate ion, the titanium is precipitated as the hydroxide by means of ammonium hydroxide, and the filtered and washed precipitate is dissolved in dilute hydrochloric or nitric acid and diluted to the desired volume. An alternative method is fusion of the oxide with sodium peroxide, followed by extraction with water and decomposition of the peroxide with acid and sodium sulfite. Vanadium may be conveniently used in the form of sodium vanadate which is readily soluble in water. Since vanadates recipitate in group I11 only in the presence of other members of e!lt group, it is essential that at least one such metal be present when testing for vanadate. The filtrate from group I1 is treated with hydrogen sulfide in the presence of ammonium chloride and ammonium hydroxide in the usual manner. A little more ammonium hydroxide should be added before filtration, in order to overcome the possible formation of soluble ammonium sulfovanadate. After filtering off the group I11 precipitate, the filtrate should be acidified with acetic acid and boiled to remove hydrogen sulfide. A brownish precipitate containing some of the vanadium may be formed at this point, and should be filtered off and added to the precipitate of group 111. The solution will contain groups IV and V. The entire precipitate of the group is suspended in 50 cc. of N hydrochloric acid, and the mixture is thoroughly stirred, allowed to stand from 3 to 5 minutes, and filtered. The residue may contain the sulfides of nickel and cobalt. The filtrate is evaporated to about half its original volume to remove hydrogen sulfide and part of the mineral acid. It is then made neutral with 5 N or 6 N sodium hydroxide, and 10 cc. of sodium hydroxide are added in excess, together with 10 cc. of 3 per cent hydrogen peroxide. Sodium peroxide may be substituted here if desired. The mixture is boiled for at least 5 minutes to decompose the excess of peroxide and insure the complete precipitation of the titanium. After being cooled, the mixture is filtered to separate the iron division from the aluminum division.
DETECTION OF TITANIUM IN THE IRON DIVISION The precipitate may contain ferric hydroxide, titanium hydroxide, and manganese dioxide. A common method for the separation of these with other metals includes the pre-
cipitation of the manganese by boiling with potassium chlorate and nitric acid, but this is not advisable in the hands of a large class because of the acid fumes that are evolved and because under these conditions much of the titanium may be precipitated with the manganese (2). Furthermore, ammonium hydroxide and ammonium chloride cannot be used to precipitate the iron and titanium from the manganese because some or all of the manganese will precipitate with the
titanium. The residue of these three metals is therefore dissolved in hot dilute nitric acid, with the addition of 1 or 2 drops of hydrogen peroxide. if necessary to effect solution. The excess hydrogen peroxide must be removed by boiling. The cooled solution is made neutral with ammonium hydroxide and a slight excess of dilute nitric acid is added to decompose any hydroxides that may be present. To this solution a suspension of barium carbonate in water is added until an excess remains undissolved. Upon standing for at least 3 minutes with occasional stirrin the excess of nitric acid is neutralized by dissolving some of tf;e barium carbonate, and the hydrogen-ion concentration in the resulting solution is such that all of the iron and titanium is completely precipitated as hydroxides while the manganese is left in solution. The use of a soluble base in place of the barium carbonate would result in the precipitation of part or all of the manganese. After filtration the lead dioxide test for manganese is made. The residue, including some excess barium carbonate along with the titanium and iron, is dissolved in dilute hydrochloric acid, and, after the addition of 1 gram of ammonium chloride, the titanium and iron are precipitated by an excess of ammonium hydroxide. The precipitate is filtered off to remove the soluble barium salts which would interfere with later tests. The residual hydroxides of titanium and iron may be dissolved in hydrochloric acid and the iron extracted with ether (2). Ether extraction may be avoided by making use of the fact that titanium phosphate will not be precipitated in the presence of an excess of hydrogen peroxide (1). The hydroxides of the two metals are dissolved in dilute sulfuric acid. To this are added 5 cc. of hydrogen peroxide, some sodium hydrogen hosphate, and an excess of sodium hydroxide. The residue of Ferric hydroxide and ferric phosphate is filtered off and the test for iron made in the usual manner. The filtrate is made slightly acid with dilute sulfuric acid, the formation of a yellow or orange solution a t this point indicating the presence of titanium, and is then treated with sodium sulfite and a little more phosphate and warmed. After the reduction of the peroxide, the formation of a white precipitate of TiOHP04 proves the presence of titanium. If the solution is too strongly acid for this precipitate to form, it should be neutralized with sodium hydroxide.
Novemher 15,1934
IN D U ST R I A L A N D E N G I N E E R I N G C H E M I S T R Y
449
and the zinc is detected in the filtrate by the DETECTION OF VANADIUMIN THE ALUMINUM DIVISIONhydroxide, hydrogen sulfide. The filtrate from the treatment with sodium hydroxide and sodium peroxide may contain sodium chromate, vanadate, aluminate, and zincate.
If it is just acidified with dilute nitric acid (1 to 3) and an excess of 3 cc. of acid are added for each 50 cc. of solution, the chromate may be removed as the lead salt upon the addition of an excess of lead nitrate. After filtration, the presence of chromium is confirmed by the use of nitric acid and hydrogen peroxide. If to the filtrate 1 or 2 grams of ammonium acetate are added, the pH will be sufficiently increased to cause complete precipitation of the vanadium as Pb,(VO&. As little as 0.5 mg. of vanadium may be detected in this way after the removal of the equivalent of 50 mg. of potassium chromate as the lead salt. The lead vanadate is filtered off and washed thoroughly to remove soluble lead salts, which would otherwise interfere with the end test for vanadium. Three or four drops of dilute ammonium hydroxide are poured over the lead vanadate on the paper and washed through with 5 cc. of water. This solution is then saturat,ed with hydrogen sulfide to yield a red solution of ammonium sulfovanadate, (NH4)aVSd,if vanadium is present. The filtrate from the lead vanadate is treated with 3 or 4 cc. of 3 N hydrochloric acid, and the excess of lead is precipitated by the use of hydrogen sulfide. The lead sulfide is filtered off and washed with 5 or 10 cc. of N hydrochloric acid to dissolve any zinc sulfide that may have been precipitated because of the presence of the ammonium acetate. After the removal of the sdfide by boiling, the aluminum is separated by ammonium
us8
of
Solutions which may contain tungsten, molybdenum, titanium, and vanadium in addition to the common metal ions have been issued t o the author's students as unknowns near the end of a semester course in elementary qualitative analysis, with satisfactory results. Not only do the students appear interested in the direct contact with these metals, which they recognize as of considerable commercial importance, but they are introduced to many of their properties, including several oxidation and reduction reactions with their several striking color changes. There is also ample opportunity for class discussion of the theory involved, such as the influence of hydrogen-ion concentration in making possible the separation of chromate and vanadate as the lead salts.
LITERATURECITED (1) Browning, P. E., Simpson, G. S., and Porter, L. E., Am. J . Sei., 42,106 (1916). (2) Noses, A. A., Bray, W. C., and 30,481 (1908).
Spear, E. B., J . Am. Chem. Sot..
(3) Porter, L.E., IND.ENG.CHEW,Anal. Ed., 6 , 138 (1934). RECEIWDJuly 12, 1934. Research Paper 355, Journal Series, University of Arkansas.
Potentiometric Titration in Nonaqueous Solutions 11. A Source of Error in Acidimetry LELPNDA. WOOTENAND A. E. RUEHLE,Bell Telephone Laboratories, New York, N. Y.
I
N ACIDIMETRY in butyl
I n acidimetry in alcoholic solution a weak
khitg'';
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~ ~ ~ ~ ~ or amyl alcohol solution, acid, resulting from oxidation of the alkali work reported. The solvent was using as reagent an alkali solution, may be introduced into the system as metal hydroxide in the same P $ ~ ~ ~ t ~f ~~t ~ ! ' ' ~ l l ~ ? ~ ~ ; the alkali salt. A simple quantitative tesf for carried out at reduced pressure (30 solvent, several workers have rethe presence of impurities, in the form of weak ported the appearance of anomalous points of inflection on the acid salts or weak bases, in the alkali solution oxide as a dehydrating agent. titration curves (or maxima on may be made by titrating portions of standard w ~ ~ ~ ~ ~ ; $ ~ ~ ~ l f $ o ~ the AEIAV curves) of both used picric acid. acidimetric reagent was found to oils and single monobasic acids offer several advantages over po(b,3 ) . Recently, in t i t r a t i n g tassium or sodium h y d r o x i d e . picric, trichloroacetic, and dichloroacetic acids in butyl alcohol This reagent, prepared by the interaction of metallic sodium and solut,ion the authors have obtained similar titration curves pure n-butyl alcohol in a reducing atmosphere, is carbonate-free (Figure 1). The appearance of two inflection points on the and is reasonably stable if properly protected from light and the atmosphere. This may be conveniently accomplished by storing titration curve of a monobasic acid can be attributed only under hydrogen in a light-proof bottle. t o the presence, as a n impurity, of a considerably weaker or Deterioration of t8healkali solution is indicated by a decrease stronger acid than the one being titrated. A systematic in neutralizing value in terms of benzoic acid, which is Itccomsearch for the source of this impurity has led to conclusions panied as the solution ages by the appearance of a yellow color and a slight turbidity. A quantitative test for the purity of the which are of general importance in connection with the use alkali reagent is described in the last section of this paper. of alcoholic solutions for precise acidimetry. The quinhydrone used in most of the work QUINHYDRONE. was obtained from the Eastman Kodak Company. RecrystalliAPPARATUS zation from butyl alcohol did not perceptibly improve its quality. The apparatus used consisted of a thermionic titrometer, Quinhydrone prepared by the method of Valeur ( 7 ) was used an electrode system, a t h a t i o n cell, and a storage system for in a few titrations. The quinhydrone was stored in a dark bottle and was dissolved immediately before use. alkali solution such as those previously described (1). The collection of the data in this paper was facilitated by the SOLVENT.The solvent employed in most of the work was the use of the thermionic tit,rometer, by which the slope of the titra- practical grade of n-butyl alcohol supplied by the Eastman tion curve is read directly. This instrument also made possible Kodak Company, used both with and without further purithe elimination of neutral salts such as lithium chloride, which fication. The method of purification employed was distillation have heretofore been used to reduce the resistance of butyl at reduced pressure from barium oxide. alcohol solutions (4, 5 ) . BLANKON REAGENTS.The value of the blank titration on 100 cc. of solvent containing 50 mg. of quinhydrone usually was REAGENTS found to be 0.05 cc. or less of 0.05 N alkali solution. If the ALEALI SOLUTION.A solution of potassium hydroxide in blank exceeded this value the solvent was redistilled as described n-butyl alcohol (0.05 N ) , prepared and stored as described in above.
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