inose. Sorbose, xylose, and fructose are notable exceptions; each yields about tn-ice as much color per milligram as the standard. The methyl sugars fucose and rhamnose as well as 01methyl glucoside yield substantially less color than might be expected on a milligram basis. Glucosamine hydrochloride, ascorbic acid, and malic acid showed no perceptible color a t a concentration of 10 mg. per liter. The reactivity of the carbohydrates is dependent to a large extent upon their structure, n hich probably explains much of the variation in the data of Table IV. d comparison of the color produced by arabinose n-ith that jielded by its primary degradation product, furfural (9), mould indicate about a 55% conversion of arabinose to furfural by this method. Because arabinose has been found t o produce 76% of its theoretical yield of furfural (6) apparently only a two-thirds conversion is accomplished under the conditions of this method. DISCUSSION
The method described has been used for several thousand determinations, both routine and experimental, and \vas found to be simple in operation and relatively rapid. The lack of salt effect makes it readily usable for sea water as well as for biological fluids. Lewis and Rakestraw (8) have used both the Erdnian i17-ethylcarbazole and anthrone methods for determining total
carbohydrates in sea water and concluded t h a t the two methods r e r e approximately equal in sensitivity t o most sugars, but that anthrone was much less sensitive to arabinose and xylose. The sensitivity of the Nethylcarbazole reagent has been increased a t least three times by the modification described here; 3 y of total carbohydrate per sample (1 mg. per liter) may be determined accurately. This compares favorably with other general methods of carbohydrate determination such as indole and sulfuric acid, 1-naphthol and sulfuric acid, or tryptophan and sulfuric acid, all of which require samples containing 10 y of carbohydrate per ml. (4). Only the cysteine, carbazole, and sulfuric acid method of Dische and Borenfreund (5) is as sensitive, and in that method the color maximum is not developed for 18 hours. Although most of the routine work 1%-as done n-ith the Fisher Electrophotometer with the special interference filter, the method is equally adaptable to the use of the Beckman spectrophotometer without a n y decrease in speed of analysis. I n the latter case it is recommended that readings be made a t 560 mp in accordance rrith Table IV, unless the sugars being determined are known t o be pentoses. Furthermore, a 5-cm. cell should be used for concentrations below 4 mg. of carbohydrate per liter, t o increase the accuracy of the readings.
With the precautions mentioned, this method is easily adaptable to routine use. Under ideal conditions, 96 samples can be run during the norking day. Slight modifications in the time of heating may be made if the standards are run in the same manner. Variations in sample volume are also possible; the method is adaptable to biochemical or clinical work using 1 ml. of sample, if the ratio of 9 parts of reagent to 1 part of sample is maintained, and if about one fifth of the total volume of reagent is added before the standing period. LITERATURE CITED
(1) Collier,
-4., ,4m. Wildlife Conf., Trans. 18, 463 (1953). (2) Collier, A., Ray, S. M., Magnitzky, W., Science 111, 151 (1950). (3) Collier, A,, et al., G. S. Fish Wildlife Serv. Fishery Bull. 54, 167 (1953). (4) Dische, Z., Jlethods of Biochem. Anal. 2,313 (1955). (5) Dische, Z., Borenfreund, E., J . Biol. Chein. 192, 583 (1951). (6) Dunlop, A. P., Peters, F. S.,“The Furans.” ACS Monograph Series, Yo. 119, p. 292, Reinhold, K e v i York, 1953. ( 7 ) Erdman, J. G., Little, h.B., “.bdysis of lfarine Coastal and Estuarial Waters,” p. 50, 11350. PIIultiple Fellowship of Gulf Resparch and Developnient Co. at llellon Institute, Pittsburgh (unpublished ’r . 18) Lewis, G. J., Jr., Rakestran-, S . W., J . X a r i n e Research (Sears Foicndation)
14,253 (1955).
(9) Rice, F. A . H., Fishbein, L., J . Am. Chern. SOC.78, 1005 (1956).
RECEIVEDfor revieiv August 17, 1957. Accepted June 30, 1958.
Determination of Titanium with Cupferron (Ethylenedinitri1o)tetraacetic Acid as Masking Agent K. L. CHENG Mefals Division, Kelsey-Hayes Co., New Harfford,
b In the presence of (ethy1enedinitrilo)tetraacetic acid, cupferron precipitates titanium, uranium, tin, and beryllium in a slightly acid medium. It also forms white precipitates or complexes with aluminum, iron, hafnium, zirconium, niobium, tantalum, and rare earths when they are present in relatively large amounts under similar conditions. The complexes of titanium, uranium, and cerium are yellow and the others are colorless. They can b e extracted b y 4-methyl-2-pentanone and other ketones, and absorb strongly in the near-ultraviolet and ultraviolet regions. The use of the masking agent and the solvent extraction make this
N. Y.
method for titanium simple, sensitive, and highly selective. The range from 2 to 300 y of titanium in 1 ml. of 4methyl-2-pentanone can b e determined spectrophotometrically. With no prior separation, this method should be applicable to routine analyses of titanium in various types of samples. Traces of uranium and cerium may be tolerated.
T
HE IMPORTANCE of titanium in the fields of steel and high temperature alloys suggests the need for a simple and sensitive method of determining this element. Titanium is frequently
determined colorimetrically by the hydrogen peroxide method which requires the absence of tungsten, molybdenum, chromium, vanadium, niobium, tantalum, etc. Most organic reagents that give a color with titanium have one structural feature in common, an enediol group, or at least one or more hydroxyl groups attached to a n unsaturated carbon-carbon linkage ( 3 ) . These titanium complexes are very soluble in water and generally are not extractable by organic solvents. Cupferron is another type of sensitive color reagent for titanium, and its colored complexes are soluble in many organic solvents (9). Elving and Olson ( I ) reported graviVOL. 30, NO. 12, DECEMBER 1958
1941
Table I.
,,
Reactions of Metals with Cupferron
H
Li I
iYa Sc
d@
Cr 1 I n @s
b ) 110 Tc? Ru? .-, k--.
Y
:Zr] c-.
La* (Hf) Fr? Ra? Ac
b c
.-*
,--
+
$;:;
K Re Os
He
-
APPARATUS A N D REAGENTS
Co Si Cu Zn Ga
As,&
Rh Pd Ag Cd In
iSn.2 Sb Te I
Ir
Pb
Pt ALI Hg T1
Br Kr ;Ye
Bi Po? At Rn
I------
1
S p ? Pu? Am? Cm? Bk? Cf?
Es?
Ct?
Md? 102? 103?'
0 Precipitation occurs in absence of complexing agents under proper conditions. In presence of EDTA and citrate at pH 5.5) white precipitate and colorless in 4 methyl-2-pentanone. 0 In presence of EDTA and citrate at pH 5 . 5 , yellow precipitate or coloration. Fe(II1) and V(V) do not give coloration in 4-methyl-2-pentanone. ? Elements not tested. Arabic figures indicate valence states. Fluoride prevents precipitation of -41, Be, Ce(IV), and U(V1).
,:!
Figure 1.
Absorption curve
-50 y of titanium in 10 ml. of 4-methyl2-pentanone ----Reagent blank
SO0
WAVE LEN(ITH M i
metric and volumetric methods of determining titanium with cupferron. KO method was found in the literature which used titanium cupferrate for the photometric determination of titanium because of lack of selectivity, stability, and a suitable solvent for the extraction of the colored complex. The use of (ethylenedinitri1o)tetraacetic acid (EDTA) as a masking agent for the determination of titanium as titanium oxide (5) and as titanium oxide after the precipitation and ignition of titanium cupferrate (4) has been re1942
ANALYTICAL CHEMISTRY
4methyl-2-pentanone or other solvents. The method described is so highly selective that, in most cases, no prior separation is required.
ported.fThe colloidal properties of titanium hydroxide make the filtration very difficult and this same difficulty was encountered when the precipitation of titanium cupferrate was made in the presence of E D T A and its metal complexes a t p H 4 to 7 . This paper describes a simple and highly selective photometric method for determining titanium, which is based on the fact that, under carefully controlled conditions, only titanium, cerium, and uranium give colored complexes with cupferron that can be quantitatively extracted by
The absorption spectra measurements were made with a Cary Model 14 spectrophotometer using 1-em. silica cells. The effects of variables were measured mith a Beckman Model B spectrophotometer or a Bausch & Lomb Optical Co. Spectronic-20 colorimeter. A Beckman p H meter Model H 2 was used for all p H measurements. Standard titanium solution, prepared from potassium titanium oxalate and standardized gravimetrically using cupferron as the precipitant, followed by ignition of the precipitate to titanium dioxide. The Xational Bureau of Standards titanium dioxide may also be used (1). (Ethylenedinitri1o)tetraacetic acid solution, O.1M disodium salt. Buffer solution. A solution of 1 mole of sodium acetate was mixed with 0.8 mole of acetic acid and diluted to 1 liter. The solution was adjusted to p H 5.5. The solutions of diverse ions used in the study of interferences and other chemicals rrere of analytical reagent grade. Cupferron. Products from G. Frederick Smith Chemical Co., Columbus, Ohio, or J. T. Baker Chemical Co. were suitable without further purification. 4-11Iethyl-2-pentanone, Eastman Kodak, white label. The technical grade (better than 99%) from Union Carbide Corp. was also satisfactory. DISCUSSION
Color Reaction. Titanium reacts with cupferron to give a yellow complex exhibiting strong absorption in t h e ultraviolet and near-ultraviolet regions. This reaction is not specific for titanium because cupferron forms precipitates and coloration with most polyvalent metals. I t s specificity can be increased greatly by using E D T A as a masking agent and 4-methyl-2pentanone as an extracting solvent. Among all common metals tested, only titanium, iron, vanadium, cerium, and uranium gave yellow precipitates or complexes with cupferron in the presence of E D T A a t p H values from 5.5 to 5.7 (Table I). The interferences of iron and vanadium can be eliminated as described later. Neocupferron gave the same reactions as cupferron under the conditions employed without any advantages, possibly because the product obtained from Matheson, Coleman &. Bell Division, Matheson Co., Inc., being rather crude, gave a high blank. Choice of Wave Length. T h e absorption spectra for cupferron and its titanium complex tvere determined as shown in Figure 1. Both cupferron and titanium cupferrate absorb a t the
near-ultraviolet region n ithout showing t h e maximum. Any mare length from 350 to 450 mp may be used for quantitative measurements, depending upon the sensitivity desired. Beer’s Law. T h e calibration curves followed Beer’s law a t 350, 400, a n d 425 mp. A wide range (from 0.5 y to 0.5 mg. in LO nil. of solvent) of titanium may be determined b y the cupferron extraction method. The absorptivity of titanium cupferrate was approximately 6200 a t 350 mp. Effect of pH. Cupferron reacts with titanium ]Tithin a very wide p H range. I n considering t h e masking action of EDT.2 and solvent extraction, a pH from 5.5 t o 5.7 11-as used in all determinations (Figure 2). Experiments indicated t h a t below pH 5.5 vanadium(T-) interfered. Above pH 5.7, t h e absorbance of t h e titanium complex decreased rapidly a n d a t a pH above 7 , t h e formation of t h e complex n-as almost completely inhibited. Amount of Reagents Required. Cupferron in aqueous solution decomposes rather fast, because of air osidation. T o obtain a low blank, a freshly prepared cupferron solution should be used. Theoretically, titanium reacts n-ith cupferron a t a 1 t o 4 ratio ( 1 ) ; however, a slight excess of cupferron should be added. The
amount of EDTA required depends on the total amount of interfering nietals present in the sample. Too great a n excess of EDT-4 inhibits the titaniuni reaction with cupferron (Figure 3 ) . Too much excess cupferron mag cause interference from iron or other metals; from 50 t o 7 5 mg. of cupferron for 25 ml. of solvent are recommended (Figure 4 and Table 11). Solvent Extraction. Isobutyl alcohol, isoamyl alcohol, and petroleum ether were found t o be poor solvents for t h e extraction of titanium cupferrate. Chloroform, carbon tetrachloride, benzene, a n d dichlorobenzene were fairly good solvents for extracting titanium cupferrate in pure solution. Toluene, benzene, and carbon tetrachloride tended to become turbid on standing. Several ketones proved t o be excellent solvents for the comples. and 4-methyl-2-pentanone n-as found to be the best among them (Table 111). As expected, 4-methyl-2-pentanone was superior t o 2-pentanone, because the former gave easier separation than the latter when large amounts of salt nere present. Iron(II1) formed yello\i- or brownish complexes with cupferron in the presence of EDTA at pH 5.5. When cupferron was added in excessive amounts, ferric cupferrate precipitate was formed which could be extracted b y 4-methyl-2-pentanone and other solTable
o{
(120
. 1 7 100 Y TITANIUM
L
\
I 7
Figure 2.
Ill.
vents. However, with a n optimuni amount of cupferron, a brownish watersoluble iron cupferrate solution was obtained n-hich could not be extracted by 4-methyl-2-pentanone. This suggests that cupferron formed a stronger complex with titanium than with iron, and that, with an insufficient amount of cupferron, the positively charged ferric cupferrate complex was formed which was not soluble in the ketone solvent (Table 11). I t is important, Table
II.
Amount of Cupferron and Iron Interference Titanium taken 110 y EDTA added 0 6 mmole Solvent 10 ml.
5 5 55 ml.
PH
Volume cupcupferron ferron Added, in Blank, Mg. 1
Mg.
3 5 10
20
20 20 20 20 20 20
25
20
2
30 35
50 100
Absorbance, 425 Mp 0 1 mmole No Fe(II1) iron present present
50
50
50 50
0.000 0.000
0.030 0.050 0.185 0 270 0 275 0 270 0 340 0 455
>2.000
0.000 0.000 0.030 0.050 0.200
0.265 0 273 0.270
0 280 0 300
0.340
Effect of Solvent
Ti, 10 ml. solvent, 425 mp, 30 mg. cupferron) Solvent Absorbance Remarks 0 030 4-Methyl-2-pentanol 0 095 Isobutyl alcohol 0 045 Isoamyl alcohol 0 255, 0 290 Slightly turbid on standing Benzene 0 240 Turbid on standing Toluene o-Dichloro benzene 0 265, 0 290 Good separation 0 280, 0 290 Good separation Chloroform 0 230 Good separation Carbon tetrachloride 0 280 Good separation 2-Nonanone 0 238 Good separation 2-Octanone 0 220 Good separation 2-Heptanone 0 240 Good separation 3-Heptanone 0 245 Good separation 4-Heptanone 2,4-Dimethyl-2-heptanone 0 205 Good separation 0 340 Poor separation when large amount of salt 2-Pentanone present 4-Methyl-2-pentanone 0 348 Good separation y
Effect of pH
0.22 Ye TITANIUM .-O -.-----e-
0.8 YYDLL EDTA
/*
0
MOLAk RATIO,
LOl[EDTA]/[Ti
tP*l]
4
.-
0.11 YO. TlTANlUY
I
O ~ ~ R A MCUPFERRONO.~DDED
Figure 3.
Effect of EDTA
Figure 4.
*
0.8 YYDLE EDTA
aa
h r
Effect of cupferron
VOL. 30, NO. 12, DECEMBER 1958
1943
therefore, that the optimum amount of cupferron be used and it should be added slowly with stirring as directed. Time of Standing. T h e mixture had t o stand for a t least 5 minutes after t h e addition of cupferron a n d before extraction t o obtain maximum color development. After extraction with t h e organic solvent, both t h e absorbances of t h e blank and the titanium complex first decreased slightly, and then increased gradually with time of standing. There was practically no plateau, as indicated by the curves of Figure 5, within a period of 2 hours. Fortunately, the same rate of change in absorbance for the blank and for the sample was observed. This may be due t o the slow decomposition of cupferron by air oxidation; therefore, the sample and the blank must be measured at the same time to correct such variation. Interference Studies. hhjumdar and Chowdhury (4) reported t h e selective precipitation of titanium with cupferron in the presence of E D T A . This investigation found more metals (aluminum, chromium, niobium, tantalum, zirconium, and hafnium) t h a t formed white precipitates under similar conditions. Chromium was hydrolyzed a t room temperature when citrate was absent. Heating prevented precipitation of chromium but not
T a b l e IV. D e t e r m i n a t i o n o f Titanium by Extraction o f Titanium C u p f e r r a t e in P r e s e n c e of EDTA (Titanium present. 100 y in 10 ml. of 4-methyl-2-pent anone)
Interfering Metal Added, 0.01 Mmole None
Cadmium(I1) Cobalt(11) Manganese( 11) Calcrum Magnesium Barium Strontium Chromium(III1 Zirconium(1V)' Xi0 bium( V) Tantalum(V) Thorium( IV) Bntimony(111) hrsenic(II1) Bismuth Thallium( 111) Bluminum( 111) Tin(I I ) Beryllium(11) Indium Silver Cerium(111) 1944 *
Absorbance 0,426 0.432 0.430 0.425 0.430 0.430 0,430 0.420 0.428
0.425 0.425 0.425 0.422 0.428 0.428 0.428 0.430 0.432 0.430 0.430 0.428 0.425 0.425 0.425 0,420 0.430 0.432 0.432 0.426 0.425 0.430
ANALYTICAL CHEMISTRY
0.21
to
40
60
80
IO0
1
I90
TIME (MINUTE 1
aluminum when EDTA was present. The results (Table IV) for extraction of titanium cupferrate with 4-methyl2-pentanone in the presence of EDTA indicate that the extraction procedure was more selective than the gravimetric procedure because the white precipitates gave a colorless extract. Under suitable conditions, iron and vanadium do not interfere. Small amounts of uranium(1V and VI) and cerium(IV, not 111) could be tolerated because cupferron did not give sensitive color reactions with them. Siobium and tantalum showed negative interference with the determination of titanium. Presumably both formed very stable colorless complexes with cupferron, because such interference could be overcome by introducing additional cupferron and 10 ml. of 10% tartaric acid. The presence of hydrogen peroxide prevented the formation of titanium cupferrate because it formed stronger complexes with titanium than cupferron. Large amounts of fluoride interfered slightly with the formation of titanium cupferrate but completely prevented the precipitation of cupferrates of aluminum, beryllium, cerium (IV), and uranium, but not zirconium, hafnium, niobium, tantalum, tin, and ytterbiuni. The use of E D T A as a masking agent increased considerably the selectivity of the cupferron reaction for titanium. However, it is still not specific for titanium, so the conditions should be carefully observed. If large amounts of interfering metals are present, it may be necessary to remove them before the color development. Rare Earth Metals. Cupferron precipitated t h e rare earths in t h e presence of E D T A a t p H 5.5 t o 6.5. It is believed that t h e p h I of rare earth cupferrates was slightly lower than t h a t of rare earth E D T A complexes because a large excess of E D T A inhibited t h e precipitation of rare earth cupferrates and a large excess of cupferron caused the precipitation. The competition between E D T A and cupferron for the rare earths clearly existed. The color reaction of ceric ion with cupferron is specific among the rare earths. The ceric cupferrate could also be extracted by 4-methyl-Z-pentanone and showed no maximum absorption in the visible region. The rare earths did
not interfere seriously Kith the determination of titanium because cupferron reacted preferably Kith the titanium, and all rare earths except cerium(1V) gave colorless extracts with cupferron in the organic solvents. PROCEDURE
Preparation of Calibration Curve. Exactly 0, 1, 2, 3, 4, and 5 ml. of the standard titanium solution (10 y per ml.) were pipetted into 200-1111. beakers. After addition of 1 ml. of the EDTA solution, the solution !vas diluted t o approximately 50 ml. nith nater and 1 ml. of the buffer solution as added. The solution was transferred to a 125-ml. separatory funnel. A freshly prepared solution containing 60 nig. of cupferron m-as s l o ~ l yadded, mixed, and let stand for 5 minutes. It was then extracted nith 25 ml. of 4-methyl-2-pentanone by vigorous shaking for 1 minute. The extract n-as separated and measured a t 350, 400, or 425 nip against a reagent blank. The calibration curve should be made daily to avoid slight variations. The above procedure was applied to the mixture of titanium and other meta k . previously adjusted t o p H 5.5 to 5.7. DETERMINATION OF TITANIUM I N STANDARD SAMPLES
Cast Iron, A sample of 1 gram was digested with 20 ml. of 1 to 2 hydrochloric acid on a hot plate until action ceased. T h e insoluble matter was filtered while still hot and washed a fe\\- times with 1% hydrochloric acid. After drying, the paper and residue were ignited in a n uncovered platinum crucible under good oxidizing conditions until all carbon n-as gone. One milliliter of 48y0 hydrofluoric acid and 1 mi. of 1 to 1 sulfuric acid were added and the solution was evaporated to dryness. The residue was fused a i t h 1 t o 2 grams of sodium carbonate. The melt was dissolved in 50 nil. of miter and digested for 15 minutes a t 90 to 95'. The remaining residue was filtered and washed with n-ater. The residue )vas ignited n i t h 1 grain of potassium p>rosulfate for 10 minutes. The melt was cooled and dissolred n ith a mininium amount of 231 sulfuric acid. This solution was added to the original filtrate and diluted to approximatelj- 250 mi. To a 25-m1. aliquot a slight excess of the disodium salt of EDTA (0.6 gram) 11-asadded, followed bv sufficient 6-11 aninionium hydroxide to adjust the solution to p H 5.5. The solution was boiled for 2 minutes and cooled. Then it Tyas trans-
ferred to a 125-m1. separatory funnel, and diluted to approximately 50 ml. Five milliliters of 0.4% freshly prepared cupferron iyere added dropwise with swirling. After standing for 5 minutes, the solution was extracted with 10 ml. of 4-methyl-2-pentanone. The extract was filtered through a filter paper and its absorbance was measured a t 365 mp using a reagent blank. The concentration of titanium ITas read from a calibration curve obtained as described for the eytraction of known amounts of titanium. Steel. A sample of 1.5 grams which contained 0.2 to 0.37, titanium (KBS 170) nas digested n i t h 10 ml. of 1 t o 10 sulfuric acid on a hot plate until action ceased. After filtering and washing, t h e residue I\ as dried and ignited in a platinum crucible with 3 grams of potassium pyrosulfate. T h e melt was cooled and dissolved n i t h a minimum amount of 2 M sulfuric acid. This solution \\as added to the original filtrate and diluted t o 100 nil. T o a 10ml. aliquot, 2 granis of the disodium salt of E D T A were added, followed by 6M ammonium hydroxide to adjust the solution t o pH 5.5. The solution was transferred to a 1254111. separatory funnel and diluted to approximately 50 ml. Five milliliters of 0.4% freshly prepared cupferroii solution TT ere added dropwise with swirling. After standing for 5 minutes, the solution was extracted with 10 ml. of 4-niethyl-2-pentanone for 1 minute. The extract ivas filtered through a filter paper and its absorbance n as measured a t 425 mp. The concentration of titanium was read froni a calibration curve obtained as described. For analyzing KBS 121b, 0.7 gram of the sample and 1.8 grams of disodium salt of E D T A n ere used, respectively. Clay. A sample of 0.2 t o 0.5 gram was niiued with approuimately 2 grams of sodium carbonate in a platinum ciucible and 0.25 gram of sodium carbonate was added on t o p of t h e mixture. T h e mixture was fused for a few minutes in t h e usual n a y . After cooling, t h e melt n as dissolyed with 10 ml. of 1 t o 1 sulfuric acid and 10 ml. of 48% hydrofluoric acid, and evaporated to approxiniately 5 nil. The solution was then transferred to a 250-ml. volumetric flask and diluted to volume. An aliquot containing approximately 0.2 to 0.5 mg. of titanium was taken for the color development, followed by 10 nil. of 10% E D T A solution and 6 M ammonium hydroxide to adjust the solution to pI-1 5.5. iifter the addition of 5 ml. of 1.27, freshly prepared cupferron, the solution was extracted with 25 ml. of the solvent. The absorbance of the extract was measured a t 425 nip and the titanium content v-as determined from a calibration curve as described before.
Table
V.
Determination of Titanium in Standard Samples
Titanium, 7 0 Present Found 0.035 0.0355
Titanium Dioxide, % Present Found
Cast iron, NBS 107A ... ... 2:38 2:40 Flint clav NBS 97 ... ... 1.43 1.43 Plastic ciay XBS 98 Steel ... B.O.H. (Ti-bearing) NBS 170 0.23 0.223 Cr-Xi (18-10 Ti) NBS 121b 0.416 0.420 High temperature alloya Udimet 5257-3 2.97 3.00 2.87 2.89 Waspaloy 5237-1 Waspaloy 2210-1 3.31 3.33 Waspaloy and Udimet are nickel-base alloys which contain approximately 14 to 20% Co, 20% Cr, 4% N o , 3% Ti, 1 t o 3% Al, 0.2% Fe, 0.05% Mn, 0.1% Si, 0.02% Zr, and other trace elements.
Table VI.
Accuracy and Precision
Titanium, yo PresFound ent" 2.87 Waspaloy 2.87 2.89 5237-1 2.85
Waspaloy 3.31 2210-1
2.84 2.88 3.28 3.32 3.36 3.31
Udimet 2.97 5257-3
Std. Dev., Dev.,
%
%
0 0.il SO.7
-0.7 -1.0 +0.3 -0.9 0.94 +0.3 fl.5 0
3.33 3.33 3.32 3.36 3.00 3.01 2.98 3.00
+O.G
3.00 3.01 3.02 3.00 3.02 3.04 2.95
$1.0 +1.3 + I .7 $1.0 $1.7 +2 3,
3.00
+0.6 +0.3 +l.5 $1.0
1.34
$1.3
+0.3 +1.0 $1.0
-0.
i
$1.0 a Determined by gravimetric cupferron method after mercury cathode and other separations. 3.00
purposes. The solution was made slightly acid and heated for a few minutes to hasten the reaction of E D T A and chromium. The solution TTas cooled and adjusted t o pH 5.5. Five milliliters of 1.5% freshly prepared cupferron were added and the solution n-as extracted with 25 ml. of the solvent. The absorbance of the extract \Tas measured a t 425 mir and the titanium content was determined from a calibration curve as described. Accuracy a n d Precision. T h e accuracy of t h e proposed method is satisfactory, as demonstrated b y t h e results shown in Table v. Table V I indicates t h a t this method has a standard deviation of approximately 1%. After t h e sample is in solution, t h e determination of titanium b y this method can be made m-ithin 30 minutes. ACKNOWLEDGMENT
The author wishes to express appreciation to Peter Salvagni and Sharon Kinney for aid in obtaining some of the data reported. LITERATURE CITED
Nickel-Base Alloy. A sample of 0.1 t o 0.2 gram was dissolved with 3 ml. of concentrated hydrochloric acid and 1 ml. of concentrated nitric acid in a 200-ml. beaker and heated gently. T h e solution was filtered and washed, and t h e residue was ignited, if necessary. (Because little residue vias found after the digestion of samples of Waspa1oy and Udimet, the steps of filtration and ignition were omitted.) The solution was diluted to 250 ml. To a n aliquot of 25 ml., 0.5 gram of the disodium salt of E D T A was added for masking
(1) Elving, P. J., Olson, E. C., AXAL. CHEM. 27, 1817 (1955).
(2) Furman, N. H., Mason, W. B., Pekola, J. S., Zbid., 21, 1325 (1949). (3) Hines, E., Boltz, D. F., Ibid., 24, 947 (1952). (4)Majumdar, A. K., Chowdhury, J. B. R., Anal. Chim. Acta 15, 105 (1956). (5) Pfibil, R., Schneider, P., Collection Czechoslov. Chem. Communs. 15, 886 (1950). RECEIVED for review April 2, 1958. Accepted July 23, 1958. Division of Analytical Chemistry, 133rd Meeting, ACS, San Francisco, Calif., April 1958.
VOL. 30,
NO. 12, DECEMBER 1958
1945
