1443
V O L U M E 2 8 , NO. 9, S E P T E M B E R 1 9 5 6 cystem, and the system is flushed clean by pumping distilled water through it.
Table 111.
Fluoride in Radioactive Solution of Fluoride Salts
EXPERIMENTAL EVALUATIOY OF APPARATUS
\.j-iiiI.
The apparatus was evaluated by determining the fluoride raontent, of uranium tetrafluoride; no accelerator was used in the jq.rohydrolysis. The results of 11 consecutive determinations 011 t w t portions t h a t ranged in size from 10 to 58 mg. are given in Table I. The relative standard deviation of these test result? i. :3%. A solid sample that \\-as principally a mixture of uranium fluorides and alkali-metal fluorides, and had been shown by macro;iiialysis t o contain 41.6 weight % fluoride, F a s also analyzed by iize of the apparatus. Aluminum oside was used as the accelt~ratorfor the pyrohydrolysis reaction; the test portions of the 5:iniple were bedded in 0.5 gram of alumina and hydrolyzed for 1i0 minutes. The results of the three determinations of fluoride :tre given in Table 11. The average of these results agrees satist'artorily with the value obtained by use of the macroapparatus. The apparatus was also evaluated by the analysis of a radio:irtive solution of fluoride salts that was prepared to contain 2 3 ~1.p.m. of fluoride. The solution was 1M in nitric acid and also contained thorium, 7.3.1l; aluminum, 3.0M; vanadium, 1.5M; iron, 0.0lX; nickel 0,OlM; and chromium, 0.01M. T h e test portion of the sample \vas absorhed in the bed of aluminum oside accelerator in the 1)yrohydrolysis crucible. -4pellet of sodium hydroxide was also included in the crucible charge. This provided a sufficiently wluble residue from the high-temperature pyrohydrolysis reacrion to permit subsequent cleaning of the crucible Tvith a miniilium of handling. T h e charged crucible was nest' positioned in t l i r b cold apparatus. After the superheater was heated to 1100" C. :inti the suc-tion turned on, the temperahre of the crucible furnace v.:ts elevated sloi\-ly. T h e volatile constituents of the test portion
t c a t portions)
Determination
Fluoride, P.l'.M.a 23
ti
\\-ere thereby removed M o r e the niasimum supply of si11)w1irl:ited steam came in contact with the test portion. The results of the annlysis of the sample are given in T:rl)le 111. The agreement I)et'ii-een the amount of fluoride :iddc~i:iiitl that recovered is sntisfactory, especially for the .small fluoiitlr concentration conccrnetl. \CliNOWLEDGRIENT
The authors wish to acknoxledge assistance receivtd I I T J I ~ I I). ,J Fisher, H. L. Hemphill, and P. F. Thomason. L I T E H T U R E CITED
Goddu, 11. F.. Hrmie, n.s., . ~ N A L . C H m f . 26, 1710 (l!L54). Sichols, 11. L.. Kindt., B. H., I b i d . , 22, 785 (1950). Susano, C . D., XVhite, J. C . , Lee, J. I?., Jr., Ibid., 27, 453 (195.5). Vogel, R. C . , .irgonne Sational Laboratory, private coniiiirinicstion t o AI. T. Kelley, June 1952. (5) R-arf, J. c y . , Cliiie, I\-. D . , Tevebaugh, It, D., . ~ N A I . . CHEJI.26, 342 (1954).
(I) (2) (3) (4)
RECEIT-ED for review l l a i 1.11 2 2 ,
l!l,jlj,
;\ccepted .June -1, 19.56
Rapid Photometric Determination of Magnesium in Electronic Nickel C. L. LUKE
Bell Telephone Laboratories, lnc., M u r r a y Hill, N.
J.
The photometric oxine method €or the determination of magnesium in nickel has been modified to permit rapid determinations. 1nterfe;ence is eliminated by removing certain interfering metals with an ammonium hydroxide separation and by masking others with c? anide.
T
HE photometric osine method for the determination o f mag-
nesium in nickel ( 1 ) gives reliable results, but is time-con-uming because of the number of separations involved. Bernuw most of the nickel samples submitted for analysis contain less than 0.01 % calcium, and because interference due to this nietzl is not serious, it seemed probable that the previously published method could be greatly simplified if no attempt was made to remove the calcium. This has proved to be true. By removing manganese with the hydroxide precipitate, rather than n-ith cartinmnte, and by masking with ryanide the interference d u to ~ nickel>cobalt, and the like, it has been possible to reduce the tinie oi :jiialyPis t o about 15 minutes. REAGENTS
Nickel Metal. The nickel metal used in the preparation of the cnlihration rurve should not contain more than 0.001 5 mag-
nesium or 0,005To cdriuni. zinc, clitiiiiium, or gallium. (Sivatc supplied by Vacuum Metals Corp., Syracuse, S . Y., has proved to be satisfactory.) Ferric Nitrate Solution. 1)issolvc 2 grams of pure iron ill 25 nil. of nitric acid (1 t o 1): heat to expel osides of nitrogen, cool, dilute to 200 ml. with x-ater, and mix. Ammonium Persulfate Solution. Dissolve 1 gram of :inimonium persulfate in 100 ml. of water. Prepare fresh each day as needed. Sodium Cyanide Solution. T1,uiisfei. 20 grams of sotliuin cyunide to a 500-ml. polyethyle~iebottle. Add 200 ml. of n-nter :irid swirl to dissolve. Keep stoppered when not in use. I'ROCEDURE
Preparation of Calibration Curve. Dissolve five 0.100-graiii portions of pure nickel by warming gently in 2-ml. portions of nitric acid (1 to 1 ) in covered 125-m1. conical flasks. hvoid unnecessary loss of acid bl- evaporation. When solution is coniplete, blow the bron-n fumes from the flasks and then cool. Traiiafer 0, 2.0, 4.0, 6.0, and 8.0 ml. of standard magnesium solution (10 y of magnesium per ml.) to the flasks and dilute each sample to 35 ml. Kith water. lldd 1 ml. of ferric nitrate solution plus 1 ml. of ammonium persulfate solution (to oxidize manganese). Add ammonium hydroxide (specific gravity, 0.90) dropwise with swirling until the iron just precipitates, then add I ml. in escess from a graduate. (The ammonium hydroxide used herc arid subsequently must not be allowed to lose its strength before use tiy standing in an open container.) Heat the solution to 6.5' C. a n d filter through R rapid 1)apor into
ANALYTICAL CHEMISTRY
1444
Table I.
1 2a
3 44 5 6' 7
a.
9 10 11 12a 13 14 15 16 17 19 18 20 Q
Magnesium,
Magnesium Found,
Other Metal Added
so.
Table 11. Analysis of Composite Samples
Specificity of Method
Ca Ca Zn Zn Cd Cd Ga Ga
56 54 50 46 46 44
~~
Found 10.0 11 2 40.0 42 40.0 30 56 80.0 4 84 0.1 ml. rather than 1 ml. of ferric nitrate solution added. 1
a
46 ~~
44 40 39 40 40 38 38 43 40 41 41 40 39
P, R e , M n
Be I n A g C i C; Zr, Au Co' Cr ' 41 W,'Bat' ir Pb Sr \lo T I ' H g k n La Bi R; I r ' P d ' O s ' R h P t K , 'Cs,'Rb,'Li,'B, de, Y, LP r Ce Nd Sm, T h T i , Se: Sb.'As T a , l i b , Si, Ge
1 ml. of ferric nitrate solution added
a 125-ml. Squibb-type separatory funnel. When filtration is complete, force the solution from the filtering funnel stem by pressure from the hand. but do not wash the precipitate. Stopper the separatory funnel and cool under running water. Wash the separatory funnel, including the bore of the stem, with distilled water. Add 10 ml. of ammonium hydroxide, swirl, add 5 ml of sodium cyanide solution, swirl, add 5.0 ml. of butyl Cellosolve solution (1 to 1 ) from a graduated pipet, and swirl. .4dd 20.0 ml. of oxine solution from a pipet and proceed to the extraction and photometric determination of the magnesium ( 1 ) . The calibration curve should be linear. Analysis of Nickel Sample. Depending on the magnesium content, transfer 0.010 to 0 100 gram of the sam le to a 125-m1. conical flask. If lese than 0.100 gram of sample $as been taken, add sufficient pure nickel to make a total of 0.100 gram of metal present in the flask Dissolve the sample in 2 ml. of nitric acid (1 to 1) and proceed as for the calibration curve. Dissolve 0.100 giam of pure nickel and carry it through the complete analysis as a reagent blank.
point before addition of the 1 ml. excess of ammonium hydroxide. The results obtained are shown in Table I. Synthetic sample solutions were prepared from aliquots of standard solutions to contain the maximum amount of metal impurities normally encountered in the analysis of electronic nickel samples. I n addition t o 0.1 gram of nickel dissolved in 2 ml. of nitric acid (1 to 1) and a measured amount of magnesium, each sample contained: cobalt, 7 mg.; silicon and manganese, 0.2 mg. of each; titanium, aluminum, and copper, 0.1 mg. of each; zinc, chromium, and calcium, 0.01 mg. of each. The sample solutions were analyzed for magnesium by the proposed method. The results obtained are shown in Table 11.
Table 111. Determination of 3Iagnesium in Nickel and Nickel Oxide Magnesium Found, Sample Analyzed
220 220 (Melt H-1400) 225 999 Cathaloy A-30 Cathaloy A-31 NBS standard sample 671, nickel oxiden
RESULTS
NBS standard sample 672, nickel oxideb
Experiments in the hydroxide separation have shown that loss of magnesium by coprecipitation or adsorption occurs if nickel and ammonium salts are not present and if the excess of ammonium hydroside added is not limited. Apparently, the presence of nickel tends to eliminate the absorptive action of the ferric hj-droxide on the magnesium. Synthetic sample solutions were prepared by mixing aliquot portions of standard solutions of nickel and magnesium. The sample solutions contained various amounts of nickel dissolved in 2 ml. of nitric acid (1 to 1 ) plus 40 y of magnesium. The sample solutions were analyzed for magnesium by the method described: the following results were obtained. Sickel P r e s e n t .
y
Added
?io*
Y
a
b
%
0,038 0.039 0,040 0.040 0.066 0.066 0,0005 0.0008 0,028 0.027 0,038 0.038 0,029 0.029 0.021 0,021
0.02970 Mg ( N B S provisional certificate). 0.020% M g (NBS provisional certificate).
Several samples of electronic nickel plus two S B S standard samples of nickel oxide were analyzed in duplicate for magnesium by the proposed method. For the nickel oxide 0.127-gram samples were used. I n order to obtain complete solution of the oxide sample, it was necessary to add a few drops of hydrochloric acid toward the end of the solution process. The results obtained are shon-n in Table 111.
Magnesium Found,
XIg.
Y
None 25
26
100
40
36
Synthetic sample solutions were prepared from aliquots of standard solutions of nickel, magnesium, and other metals. Each sample was made up to contain 0.1 gram of pure nickel dissolved in 2 ml. of nitric acid (1 to l ) ,plus 40 y of magnesium, plus 100 y of one or more of 53 other metals. The metals added were in their highest normal valence states. The sample solutions were analyzed for magnesium by the proposed method, except that 0.1 ml. rather than 1 ml. of the ferric nitrate solution was added and the solution 13-as neutralized to the methyl red end
DISCUSSION
By removing precipitatable metals by coprecipitation with ferric hydroxide followed by masking of the nickel and various other metals with cyanide, the interference of small amounts of most metals can be eliminated in the photometric oxine-chloroform extraction method for magnesium. An appreciable excess of iron must be present in order to coprecipitate interfering metals completely. When the amount of the latter present in the sample to be analyzed is small, as it is in the experiments shown in Table I, only about 1 mg. of iron is required to remove the interference completely. When larger amounts of interfering metals are present it is necessary to increase the amount of iron added. Oddly enough, gallium is not completely precipitated even in the presence of a large excess of
V O L U M E 28, N O , 9, S E P T E M B E R 1 9 5 6 iron. This does not present any problem, however, because nickel does not usually contain gallium. The interference due to nickel, cobalt, copper, silver, gold, and the platinum metals can be readily eliminated by masking with cyanide. On the other hand, the interference due to zinc and cadmium cannot be entirely suppressed by the limited amount of cyanide that can be tolerated in the osine extraction separation (Table I). Fortunately the amount of zinc and cadmium present in nickel is usually less than 0.01%.
1445 The results obtained by the new rapid method in the analysis of nickel samples (Table 111) compare favorably with those previously obt,ained (1). LITERATURE CITED
(1) Luke, C . L., Campbell, 11.E., d s a ~C.H E M . 26, 1778 (1954)
RECEIVED for review February 23, 1956. Accepted M a s 19, 1956.
Photometric Titration of Small Amounts of Barium with (Ethyleaedinitri1o)tetraacetic Acid ALLEN I. COHEN and LOUIS GORDON D e p a r t m e n t o f Chemistry, Syracuse University, Syracuse 10,
N. Y.
A method for the photometric titration of small quantities of barium with (ethylenedinitri1o)tetraacetic acid uses as indicator Phthalein Purpur, a phenolphthalein derivative having iminodiacetate functional groups. This forms a coniplex with barium which shows an absorbance maximum at 570 mg. From 0.05 to 12 mg. of barium can be determined by titration with 0.01 o r 0.002.V (ethylenedinitrilo)tetraacetic acid.
R
O K L E T , Stoenner, and Gordon ( 4 ) have proposed a phot,ometric titration for the determination of from 0.1 to 5 mg. of barium. This is a modification of the method of RIanns, 1 h c h o v s k y I and Certa (3) for macro quantities of barium, whirh \\-as determined by titration with 0.1~17E D T A solution [(ethylenedinitrilo)tetraacetic acid ] using the magnesiumEriochrome Black T comples as an indicator for the detection of the end point. Anderepg, Flaschka, Sallman, and Schwarzenbach ( 1 ) have recently proposed a compound which forms a complex with all the alkaline earths and which would appear to have some advantages as a direct indicator over the magnesium-Eriochrome Black T complex in the titration of barium.
WAVE LENGTH ( m p )
Figure 1. Absorption spectra of complex of barium with Phthalein Purpur during titration with EDTA a. S t a r t of titration ( no EDTA added) b . 4 portion of barium removed from complex b y titration x i t h EDTA c . After end point d . Untitrated blank (no added barium)
HOOCCH,, H-N-CH, -0OCCH: +
The present investigation was undertaken to study the applicability of Phthalein Purpur in photometric titrations of smaller quantities of barium, using more dilute solutions of EDTA.
OL‘“ The compound forms a purple-red complex with barium ions. The color of the indicator itself is a light pink in alkaline solution -i e., the color of phenolphthalein. T h e indicator has been called “phtalein complexone” ( 1 ) and “metallphtalein” ( 5 ) . and is conimercially available as Phthalein Purpur. Anderegg and associates have suggested the use of this indicator in a visual titration in 50% ethyl alcohol, so that the pink color of the free indicator will be suppressed. They used 0.1S E D T A in thew titrations and claimed an accuracy \Tithin 0.2 to 0.3%.
MATERIALS 4 N D EQUIPMENT
All reagents were of reagent grade quality, with the exception of triethanolamine, which was technical grade.
EDTA Solutions. Four grams of disodium dihydrogen (ethylenedinitri1o)tetraacetate and 0.6 gram of sodium hydroxide were dissolved in water and diluted to 1liter. This solution was standardized against known amounts of barium and found to be 0.01340M. iipproximately 120 ml. of this solution was then diluted to 1 liter. This solution was found to be 0.001610M as determined by subsequent standardization. Buffer Solution. A solution was prepared by adding 10 gram? of ammonium chloride to 1 liter of concentrated ammonium hydroside and storing in a polyethylene bottle. A solution of pH 1 1 was prepared by diluting 10 ml. of this buffer to 60 ml.
