1728
ANALYTICAL CHEMISTRY
tained by applying a correction factor to the observed value. The coefficient, 1.056, is the correct,ion factor ( F ’ ) to be applied to the observed phosphorus value. The constant (0.006) is smaller than the expected repeatability of the t,est and for all practical purposes can be ignored. Several samples covering many types of materials and a wide range of phosphorus content were run by this technique and by a standard method of analysis (.4). The data obtained are shon.~i in Table 111. The rapid method yields rer?ult,swhich are in good agreement with those obtained by the conventional method. Samples containing barium yield high results due to the presence of barium sulfate, which ahsorbs some of the light passing through the sample. This interference can be removed by centrifuging the sample. Table IF’ presents comparative data obtained when this type of sample is run with and n-ithout crnti,ifuging.
PRECISION
Based on the data available at this time, the precision of these determinations appears to be a8 follows: 1:lement Snlfur
1 ’ ~ ~ O ~ I15 ~ ) ~ I ~ l
Concentration Lewl (%) 1O t 0 1 to 1 0 0 05toO 1
Precision
100 10to1 0 0 05 to 0 10
0 12 0 040 0 006
(2
c)
0 11 0 05 0 02
ACKNOWLEDG31 EST
Tile authors wish to espress their thanks to E. It. Hartniann of the ERSO Research and Engineering Co., Products Research Division, for his help in making many of the analyses during this investigation.
Table 7.’. Determination of Phosphorus and Sulfur i n Same Sample Sample To
~-Phosphoius -
Calcd
Founda
2 59 0 95
2 40 0 96 2 58
13A 14A 12A a
2 5a
Sulfur ______ Calcd.
Found
2 95 0 34 2 59
2 94 0 32 2 53
Collected values
(1) ;lite.. \I-. Iliiscolored lnke does not conform strictly t o Beer’s la^. Hoivever, the rclationship of light absorption to beryllium content can be fixed by careful control of pH, dye strength, temperature, and amount of other ions present. The p H can be regulated with a sodium borat,e-citrate buffer. Magnesium and zinc interfere by reacting with the dye. These metals and also the metals that form colored ions or precipitates in alkaline solution, such ns copper, nickel.
1729
V O L U M E 2 8 , N O . 11, N O V E M B E R 1 9 5 6
Buffer solution. Dissolve 116 grams of cit,ric acid, 58.7 grams of anhydrous sodium borate, and 216 grams of sodium hydrosidc in water and dilute t o 1 liter. Dye solution, 4-(p-nitrophe1iylnzojorcinol (Eastman Kodal; P4414). Dissolve 0.150 gram of the dye in 500 ml. of 0.LV sodium hydroxide solution by stirring with a mechanical stirrer for 5 hours and filtering through an asbestos mat. Store in a red (low actinic) glass bottle. Renew this solution about once a month. Chelating solution. Dilute one volume of a 47'3 miter eolution of t,etrasodium (ethylenedinitri1o)tetraacet:ltc (Versene Regular) lvith three volumes of distilled xater ( 1 ) . Hydrogen peroxide, 3% solution. Sodium hydroxide solution, 2.031. Hydrochloric acid, specific gravity 1.18. Sulfuric acid, specific gravity 1.84. PROCEDURE
+
Dissolve 5 grams of the sample in 1 1 hydrochloric acid or 20% sulfuric acid, cool, dilute t o 100 ml., and take an aliquot containing 0.05 t o 0.6 mg. of beryllium, not more than 5 mg. of magnesium, 20 mg. of calcium, 10 mg. of iron, 35 mg. of aluminum, and not more than 100 mg. of titanium.
' 1 600 '450
500
WAVE
550
LENOTH mp,
Figure 1. Transmittance curve
iroii, and r;tlciuni, are rendc3red harmless I)>- chelation ix-itli t,lic. tptrasodium salt, of (ethl-lcnedinit'rilo)tetraacetic acid. Titanium in relativrly high concentrations as encountered ill the analysis of titanium alloys must he prevented from precipitating in the alkaline solution. This has been accomplished by the combined use of t,etrasodium (ethylenedinitri1o)tetraacetatc : ~ n d hydrogen p r o s i d e . Without hydrogen peroside thv che1:tting agent T d l not prevent the hydrolysis of titanium iii the alkaliric~solution when it is the major constituent of the sample. Titanium, vanadium, and molybdenum, which form colored romples ions with prroxide in acid solutions, do not form interfwing colors in the buffered solution. The tetrasodium salt of (c~t1iylrriedinitrilo)tetraaceticacid TWS found t o be more effective i n alkaline solution than other complesing :tgents for preventing intcrfcrence by titanium. Interference h y magnesium and b?. the ordiriary components of titanium alloys such as iron, chroniium, and vanadium, which are colored or form precipitates, was : ~ l r oPffcctivcly eliminated by use of the tetrasodium salt.
$50
I-
z W 0
a
r 10
0
Figure 2.
REAGENTS
1 ,I
.2
$3
.4
.5
.6
MILLIGRAMS OF Be/loomt.
.7
CalibraLiun curve at wave length 51.5 mg
Standard he1 yllium solution, 0 1 mg. of i)riylliiim per ml. I1)issolve 1 966 'grams of bervllium snlfatc (13rSOI.4H20) in water and dilute t o 1 liter.
Table I.
Data for Calibration Curve Be,
Nunibcr Blank 1
2 3 4
5 6 7 8
3Ig./lOO LI1. 0 00 0 05 0 10 0 20 0 30 0 40 0 50 0 60 0 70
%T 100 0 85 3 72 0 54 4 40 1 31 0 25 0 21 0 17 8
Place in a 125-ml. Erlcnmeycr flask and adjust the volume t o approximately 15 nil. Add 13 nil. of 3'7, hydrogen peroxide arid 5 ml. of the chelating solution. Adjust the pH t o 5.5 using 2.1sodium hydroxide or hl-drochloric acid as needed. Let stand 5 minutes. Add 10 ml. of buffer solution anti let stand 5 minutes. Transfer to a 100-ml. volumetric flask. Add exactly 10 nil. of the dye solution. Make up to 100 ml. with distilled water and let stand for 10 minutes. Determine the per cent transmit,tance with a spectrophotometer adjusted t o 1007, transmittance with a reagent blank which does not contain titanium. The transmittance curve, Figure 1, shows maximum absorbance near the wave length of 515 mp. The samples are, therefore, r a d a t 515 mp, using a slit width of 0.01 mm. with the Beckman Model D U spectrophotometer.
1730
ANALYTICAL CHEMISTRY
Determine the beryllium content by reference to a previously constructed calibration curve.
Table IV.
Beryllium in Experimental Alloys XI, XI - x
Aliquot
PREPARATION OF CALIBRATION CURVE
Be, %
Deviation, ’%
A1 6%. V 4%- Be O . l % , T i 90%
The calibration curve was prepared by taking a series of aliquots of the standard beryllium solution, to cover the range 0.05 to 0.70 mg. of beryllium, and subjecting them to the procedure outlined (Table I). Cells having a light path of 10 mm. were used. The curve was drawn by plotting % T against milligrams of beryllium on semilogarithmic paper (Figure 2). DISCUSSION OF RESULTS
Five synthetic samples, three of which were made by additions of a standard beryllium solution to solutions of commercial alloys, were prepared and analyzed. The composition of the samples and results of analysis are s h o m in Tables I1 and 111.
Table 11.
Synthetic Samples
Be Added,
Be Found,
70
Aliquot
%
Difference,
70
Synthetic 1. T i 9 0 % , h l o 2.0%. Cr. 2.0%, AI 6 % 0.07 0,076 f0.006 +0.004 0.07 0.074 0.70 0,684 -0.016 0.70 0.680 -0.020
A B C D
T i 9 2 % , 110 2 % , A I 4 % , V 2% 0.035 +0.005 0.028 -0.002 0.270 -0,030 0.274 -0.0’26
Synthetic 2. 0.03 0.03 0.30 0.30
A
B C D
Be Added,
%
Alloy I55AX.
Ti SS%,
Be Found,
70
Difference,
%
Fe 0.9 to 1.770, C r 0.8 to 2.095, .41 4.0 t o AI0 0.8 t o 2.0%
B C
D E F G H
I J
0.125 0.119 0.111 0.125 0.115 0.122 0.126 0.116 0.113 0.122 0.119
Ave. 2 Standard deviation 10.005% A1 6%, V 476,Be, 0.25%, T i 90% -0.009 0.246 -0,007 B 0.248 C -0.005 D 0 256 +0.003 -0.003 E 0 250 F 0 254 +0.001 G 0 256 +0.003 0 2.57 H +0.004 0 258 I +0.00.5 0,256 f0.003 J 4v. 0.253 Standard deviation 10.005%
A
AI 6 7 0 , V 4%, Be 0.50%, Ti 90% 0.475 +0.007 0.472 +0.004 0,464
-0.004
0.473 0,464 0.465 0.461 0.472 0.468
f0.005 -0,004 -0,003 -0.007 +0.004
Av.2 Standard del-iation dzO,OO5%
Table 111. Alloys w-ith Added Beryllium Aliquot
A
6.070,
ranging up to 5% of the sample R-eight. Hydrofluoric and fluoboric acids interfere when present in the solution. The color does not develop a t all in the presence of hydrofluoric acid. CONCLUSIOR’
Alloy 140.L A B C D
A B C D E
T i 93.776, F e 1.5 to 2.596, Cr 1.5 t o 2.5%, hfo 1.5 to 2.5% 0.50 0.57 +0.07 1.00 0.99 -0.01 1.50 1.60 to.10 2.00 2.00 0.00 diloy 6-41-48. 0 25 0.50 0.75 1 .oo 1.33
T i 9070, AI 6.0%, V 4.0% 0.30 0.50 0.72 1.06 1.34
+o
05 0.00 -0.03 +0.06
This method is satisfactory for practical application to the analysis of titanium alloys. The accuracy and precision compare favorably n-ith other colorimetric methods applied in the presence of titanium. ACKNOWLEDGMENT
The authors wish to acknowledge the helpful supervision of Robert L. Powell, Process Research Supervisor, Titanium Metals Corp. of America.
+0.01
LITERATURE CITED
I n addition ten determinations were made on each of three experimental alloys having beryllium contents of approximately 0.1, 0.25, and 0.50% (Table IV). The standard deviation, in each group of determinations, was less than 0.006%. The reference solution in each case was a reagent blank containing all reagents used but no sample. The elements usually present in titanium alloys do not interfere when present in the amounts normally used in commercial products. No interference was observed in the presence of up t o 2.5%iron, 2.5%chromium, 6% aluminum, 2.5%molybdenum, or 4% vanadium. The method was also checked for interference by magnesium; no interference was observed with concentrations of magnesium
(1) Bersnrorth Chemical Co., Framingham, Mass., “The Versenes,” Tech. Bull. 2, Sect. 1, p. 16B. (2) Hildebrand, W. F., Lundell, G. E. F., Bright, H. A., Hoffman, J. I., “Applied Inorganic Analysis,” p. 517, Wiley, New York, 1953. (3) Kolthoff, I. M.,J . Am. Chem. SOC.50, 393 (1925). (4) Komarovskii, A. S.,Poluektov, N. S.,X i k r o c h e m i e 14, 315-17 (1934). (5) Kosel, G. E., Keuman, W. F., ANAL.CHEM.22, 936-9 (1950). (6) Luke, C. L., Campbell, hl. E., Ibid., 24, 1056-7 (1952). (7) h k e k , H. V.,Banks, C. V., Ibid., 22, 1915-16 (1950). (8) Tour & Co., Sam, 44 Trinity Place, New York 6, iY.Y . , Rept. 10780, 17 (May 2, 1954). (9) Vinci, F. A., ANAL.CHERI. 25, 1550-5 (1953). (10) Wood, C. H., Isherwood, H., Metallurgia 39,321-3 (1949). RECEIVED for review December 5, 1955. Accepted July 19, 1956. Divmion of Analytical Chemistry, Symposium on Analysis of Titanium and Its Alloys, 128th Meeting, ACS, Blinneapolls, Minn., September 1955.
