EXPERIMENTAL
Table 1. Determination of Uranium after Separation from Bismuth
Number 1 2
U233
U233
Added,
Found,
Y
Y
415 415 415 112 112 7.27 7.27 7.27
3
4 5 6 7 8
8
1423 1422 1394 114 112 7.30 7.14 7.14
%
Deviation +O.G +0.5 -1.5 +1.8 0.0 +0.4
-1.8 -1.8
w:is found to be negligible. These solutions of uranium-233 were used to determine whether uranium is lost when bismuth is separated as the sulfide with thioacetamide from 2M nitric acid solution. The results of these studies are shown in Table I. All counting work was done with a n alpha scintillation counter.
CoIorimet ric SAMUEL
B.
ILITERATURE CITED
Flaschka, H., Chemist-Analyst 44, 2-7 ( I 055).
Latimer, W. WI., "Oxidation Potentials," Prentice-Hall, New York, pp. 114-15,1938. Swift, E. H., Butler, E. A., ANAL. CHEAT. 28, 146-53 (1956). Williams. C.. i\.l'iles,F. T., Nucleonics 12,i'i-iS (ig%ij.
RECEIVED for review August 27, 1056. Accepted November 3, 1056. G. A. Stoner is guest scientist at Brookhaven National Laboratory from The Dow Chemical Co., Midland, >lich.
KNIGHT, ROSS L. PARKS, SARAH C. LEIDT, and KENNETH L. PARKS
b A spectrophotometric study of six sulfur-containing compounds which form complexes with the platinum metals i s presented. One of the compounds, s-diphenylthiourea, has favorable colorimetric properties as a reagent for ruthenium and its stability of color, specificity for ruthenium, and compatibility with the other platinum metals have been studied in detail. A modification of the Gilchrist gravimetric method is also presented.
of ruthenium in high density alloys and its appearance in uranium fission residues have prompted a study of an applicable analytical procedure for trace amounts. Many good gravimetric methods for macro quantities (1-4, 6) are utilized after separation of the volatile ruthenium tetroxide (2,s). Volumetric redox methods using tin(I1) chloride give low results (6). A number of reagents for the colorimetric determination have been reported (2, 8, 10-12). Yoe and Overholser (12) and Sandell (7) have carefully examined the reaction of ruthenium with substituted ureas and thioureas and found them t o possess desirable properties for colorimetric work. SteiHE USE
ACKNOWLEDGMENT
The authors are indebted to W. S. Ginell, Brookhaven National Laboratory, for preparation of the standard bismuth-uranium-233 alloy.
Determination of Ruthenium
University of North Carolina, Chapel Hill,
T
Dissolve the uranium-bismuth alloy in concentrated nitric acid and transfer to a volumetric flask of suitable size to contain approximately 100 mg. of bismuth per ml. Remove an aliquot containing approximately 200 mg. of bismuth, dilute to 75 ml. with 2M nitric acid, and heat to between 50" and 60" C. Add 5 ml. of a 5% solution of thioacetamide with stirring. Maintain the temperature between 50' and 60" C. until precipitation is complete, as indicated b y a clear supernatant liquid. Filter the precipitate through IJ'hatman No. 42 paper, wash with water, and evaporate the filtrate to dryness. Rotate the beaker over an open flame until fumes cease to be evolved. Dissolve the residue in a minimum of concentrated nitric acid and dilute to volume in a 100-ml. volumetric flask. Pipet 1-ml, aliquots onto stainless steel planchets for alpha counting. Use the alpha counting rate of the standard uranium-233 solution to determine the yield of uranium after separation.
From these data it seems evident that the thioacetamide precipitation offers a clear-cut separation of bismuth with no loss of uranium.
N. C.
ger (9) has shown that substituted are less sensitive toward osmium but retain a sensitivity for ruthenium. This paper is a study of six organic thio compounds which develop colored complexes with ruthenium.
, thioureas
SOLUTIONS A N D REAGENTS
Solutions of platinum, rhodium, rhenium, iridium, and palladium (100 p.p.m. in 6 N hydrochloric acid) were made from their chlorides. An osmium solution (100 p.p.m. in GAT hydrochloric acid) was made from osmium tetroxide. Ruthenium solutions of various concentrations were made from spectroscopically ' pure ruthenium powder. Solution was effected by fusion of the ruthenium powder with an intimate mixture of approximately 4 to 5 grams of a 12 to 1 mixture of sodium peroxide and refined sugar charcoal (100 mesh) in a covered nickel crucible. The crucible was placed on an ice bath and ignited. After cooling, the resulting cake was dissolved in cold water. A test for nickel with dimethylglyoxime gave negative results. Samples as large as 0.20 gram were completely dissolved by one such fusion. The resulting solutions were then distilled as the tetroxide from a sulfuric acid-sodium bromate solution and collected in a hydrochloric acid-sulfur dioxide solution. These solutions were vigorously boiled for
30 minutes to remove all the dissolved sulfur dioxide, cooled, and diluted to 1 liter with 6177 hydrochloric acid. The ruthenium solutions were standardized by the method of Gilchrist (3) with a slight modification. The oxide was filtered through a Gooch crucible (ignited in h-ydrogento constant weight) instead of through filter paper. After the first ignition (30 minutes a t 600" C., hydrogen atmosphere) the crucible was cooled, carefully leached with hot water to remove any soluble salts, and reignited to constant weight. Results were reproducible to &;3 parts per thousand. The organic reagents s-di-o-tolylthiourea, thiosemicarbazide, 4-phenylthiosemicarhzide, s-di-p-tolylthiourea, and 2-thiobarbit~ric acid from the Eastman Kodak Co. were used as received. s-Diphenylthiourea was recrystallized from 95% ethyl alcohol. Solutions of these reagents were made up to 2%, or satur:ited if not sufficiently soluble, Glacial acetic acid was used as the solvent for all except thiosemicarbazide, which vas 291, in G N hydrochloric acid. A11 solutions were filtered through 2 inches of borosilicate glass wool before use. These reagents were stable for 3 months. Other reagents were C.P. grade and used withouit further purification, MEASUREMENTS
All transmittancy measurements were made on Beckman Models B and DU VOL. 29, NO. 4, APRIL 1957
571
I
Figure 1 .
I
B
I
Absorbance plots
A.
s-Di-o-tolylthiourea 1. 12 p.p.m. ruthenium 2. 10 p.p.m. osmium 3. 1 0 p.p.m. palladium 4. 1 0 p.p.m. rhodium
B.
Thiosemicarbazide 1. 1 6 p.p.m. ruthenium 2. 1 0 p.p.m. osmium 3. 1 0 p.p.m. rhodium 4. 10 p.p.m. palladium 5. 1 0 p.p.m. rhenium
C.
4-Phenylthiosemicarbazide 1. 12 p.p.m. ruthenium 2. 10 pap.m. osmium 3. 10 p.p.m. rhodium 4. 10 p.p.m. rhenium 5. 10 p.p.m. palladium
-
I C
-
1
800
b Figure 2.
D
Absorbance plots
D.
s-Di-p-tolylthiourea 1. 1 2 p.p.m. ruthenium 2. 1 0 p.p.m. osmium 3. 10 p.p.m. platinum 4. 10 p.p.m. palladium 5. 10 p.p.m. rhodium
a 0.2
I
mb
700
E
E.
2-Thiobarbituric 1. 16 p.p.m. 2. 10 p.p.m. 3. 1 0 p.p.m. 4. 1 0 p.p.m. 5. 1 0 p.p.m.
acid ruthenium osmium platinum rhenium rhodium
-
-
0.2
a 600
mp
?OO
800
F
F.
s-Diphenylthiourea 1, 1 2 p.p.m. ruthenium 2. 10 p.p.m. osmium 3. 10 p.p.m. palladium 4. 10 p.p.m. rhodium
a 0 2
mu 572
ANALYTICAL CHEMISTRY
7 0
0 00
Table 1.
Reagent Used nu s-Di-o-tolylBlue thiourea Thiosemicarbazide Green violet 4Phenglthiosemi- Rose carbazide violet s-Di-p-t olylBlue thiourea %Thiobarbituric Red acid ::-DiphenylBlue thiourea
Colors Developed with Metals
4-Phenylthiosemicarbazide s-Di-p-tolylthiourea 2-Thiobarbituric acid s-Diphenylthiourea
spectrophotometers cni. Cores cells.
..
30
Yellow Yellow Yellow
..
30
..
10
.
20
..
5
Re
Violet
..
..
Yellow
.,
Yellow
Yellow
..
Violet
Yellow
Rh Ir Yellow Orange
..
..
Yellow Orange Yellow
,
PPt.
*.
Rose
Wave Length, IvrF 620 435 575
ODtimum Concn. Range, P.P.M. 5-20 10-30 10-30
515 630 570 630
1-8 6-20 8-20 6-18
- I
..
The following procedure was found satisfactory in developing the colors of the various complexes. An aliquot of the metal solution, not exceeding 10 nil., was pipetted into a 50-ml. volumetric flask containing 30 ml. of a 1 to 1 concentrated hydrochloric a ~ i d - 9 5 7 ~ethyl alcohol solution. The solution was well mixed; then 5 ml. of the indicator solution and a sufficient amount of the 1 to 1 hydrochloric acid-ethyl alcohol solution were added, to bring the total volume to 45 ml. This solution was well mixed and placed in a water bath a t 85” C. for an experimentally determined length of time, depending on the indicator being used.
Table I gives the colors and times for color development. After the proper heating, the flasks were cooled in running water, diluted to volume with the 1 to 1 hydrochloric acid-ethyl alcohol solution, and well mixed, and the transmittancies were measured. The final solution must be a t least 35Y0 in ethyl alcohol to prevent precipitation. Blanks were prepared in the same manner.
The wave lengths t o be used for transmittancy measurements were obtained from absorbance plots (Figures 1 and 2). The optimum concentration range was determined from plots of log concentration us. per cent absorbance. These data are tabulated in Table I1 along with the wave length of maximum absorbance. All solutions followed Beer’s law over the optimum range. Thiosemicarbazide, s-di-o-tolglthiourea, and 4-phenylthiosemicarbaxide were eliminated as possible reagents, because of instability of color, low sensitivity, or incompatibility with other metals (principally osmium). Further work was carried out using the three remaining reagents. s-Di-p-tolylthiourea. With increasing osmium concentration (ruthenium concentration held constant) a shift in the absorbance maximum toward a lower wave length would be expected (Figure 2), and this was noted. A solu-
Effect of 8 P.P.M. of Foreign Ion on %oT tolylthiourea
of Ruthenium with s-Di-p-
A%T (at 630 M r )
os 1.5 2.3 2.8 3.2 3.4
Yellow Yellow
RESULTS
1.OO-
employing
Ru, P.P.RI. 8.3 11.1 13.9 16.7 19.5
Pd
Ycllow Yellow Yellow Red
DEVELOPMENT OF COLOR
Table 111.
Yellow
Pt
Table II. TabulationI of Log Concentration vs. Per Cent Absorbance Plots
Reagent Used .e-Di-o-tolylthiourea ‘Thiosemicarbazide
..
Time in Bath, Min. 5
os
I
‘
Ir 1.4 1.5 1.8 2.1 2.1
Pr 3.5
3.3
3.9 3.7 3.5
Rh ‘-0.3 0.3 1.0 0.8 1.4
Pd’ 2.0 2.5 3.6 4.0 4.7
tion of 14.85 p.p.m. of ruthenium and 14.21 p.p.n-~.of osmium exhibits a maximum a t 600 mp, compared to 630 mp for pure ruthenium with this reagent. A study was macle in which 8 p.p.m. of foreign metal ion was added to solutions of varying concentration of ruthenium; is recorded in Table 111 (AYoT’ = (%T ruthenium - %T mixture). 2-Thiobiubitwic Acid and s-Diphenylthiourea. This complex with
ruthenium was unstable with time (+2% T per hour), but reliable results were obtained if measurements were made exactly 80 minutes after the sample had been removed from the water bath. Palladium, which forms a red precipitate, causes a shift of the absorption maxima toward lower wave lengths. The effect of 8 p.p.m. of foreign metal ion on varying concentrations of ruthenium is tabulated in Table IV. A series of solutions nsing s-diphenylthiourea agreed within =k0.5% T with a similar series prepared separately indicating favorable reproducibility with this reagent. The variations shown in Table IV a r e considered to be within the experimental errors of the colorimetric method. A studj, was made using a series of solutions containing a constant amount of ruthenium (11.9 p.p.m.) and varying amounts o f foreign metal ions (Table 17).
A comparison of relative sensitivities of the reagents studied for ruthenium is tabulated in Table VI. These values were obtained by determining the absorbance of 1 p.p.m. of ruthenium and giving the more sensitive reagent an arbitrary value of 1.00. C0NCLUSI 0N
Of the six reagents studied s-diphenylthilourea offers the most desirable properties. However, as Table V shows, the presence of an excess of foreign ions gives questionable results. It is therefore recommended that ruthenium be separated as the tetroxide before deteirniination, if there is a possibility of‘ significant interference from a foreign metal. When ruthenium is present in excess, the distillation may be eliminated without introducing a serious error. LITERATURE CITED
(1) Flagg, J. F., “Organic Reagents in Gravimetric and Volumetric Analysis,” p. 281, Interscience, New York, 1948. Gilchrist, It., Bur. Stundurds J. Research 3, 993-1004 (1929). Ibid., 12, 283-90 (1934). Hillebrand, W. F., Lundell, G. E. F., “Applied Inorganic Analysis,” Wiley, New York, 1929. VOL. 29, NO. 4, APRlC 1957
573
~~~
~~
Table IV.
~
~
Effect o f 8 P.P.M. o f Foreign Ion on %J
Pd
Pt
Rh
Ir
I n 2-Thiobarbituric acid
Ru, P.P.M.
Table V.
0.: Ruthenium
0.6
-22.3
13.6 16.7 19.5
1.1 1.6 1.7
-15.2
5.9 8.9 11.9 14.9 17.8
-0.6
1.1
-0.8 -0.6 -0.4
-19.G -17.6
0.0 0.2
-13.6
In s-Diphenylthiourea (at 630 M u ) 0.1 0.3 . 0.4 -0.4 0.2 0.5 0.6 0.1 0.1 -0.1 0.3 0.9 0.4 0.7
(Ru
24.0
28.0 30.0
Relative Sensitivities for Reagents Studied
=
Reagent CPhenylthiosemicarbazide
-1.1 -0.4 -0,2 0.7 I .(I
-0.5 -0.2
0.6 0.3 0.3
0.0
0 0.6
s-Di-o-tolylthiourea s-Diphenylthiourea s-Di-p-tolylthiourea 2-Thiobarbituric acid Thiosemicarbazide
Relative Sensitivity 1.00 0.481 0.431 0.388 0.364 0.232
0.6
Home, J. L., J . Am. Chem. SOC.49,
0.0
0.2
0.4 0.4 0.0
0.5
Effect of Ruthenium on %J in Various Concentraticins of Foreign Ions with s-Diphenylthiourea
Concn. of Metal Ion, P.P.M. 16.0 20.0
Table VI.
A%T
os 8.3 11.1
~
11.9 p.p.m.)
2393-5 (1927). Ogburn, S. C., Jr., Ibid., 48, 2493 (1926). Sandell, E. B., “Colorimetric Dctcrminntion of Traces of Metals,” 1., 387, Tnterscience, New York, 1944. Snell, F. D. “Colorimetric Methods of Analysis,”’ vol. I, p. 418, Van Nostrand, New York, 1936. Steiger, B., Mikrochenzie 16, 193 (1934-35).
A%T‘ (630 M p )
os
Pd
0.2 0.3 0.7 0.5 0.1
1.0 0.9 1.2
1.2
1.8
Pt 1.0 1.0
1.4 2.0 3.2
Ri
Ir
0.5 0.9
1.o 1.0 1.9
1.0 0 .s
1.2
1.6
1.8
(1942).
RECEIVED for review June 19, 1956. Accepted Kovember 28. 1956.
Application of Anthrone Tesf to Determination of Cellulose Derivatives in Nonaqueous Media E. P. SAMSEL and J. C. ALDRICH The Dow Chemical Co.,’Midland, Mich.
b The extractability of ethylcellulose from films b y light mineral oil was studied in connection with food uses. An analytical procedure was developed in which ethylcellulose was extracted from light mineral oil with a mixed methanol-water solvent, then quantitatively determined with a modified anthrone method. Light mineral oil a t room temperature extracts less than 1 p.p.m. of ethylcellulose a t the end of 4 weeks. Cellulose acetate butyrate was extracted from light mineral oil with a mixed methanolacetone solvent, and was quantitatively determined with the anthrone method to an accuracy within 1 p.p.m.
A
was developed for the quantitative determination of small amounts of ethylcellulose in light mineral oil. This method was used to study the extractability of ethyl&fETHoD
574
ANALYTICAL CHEMISTRY
cellulose from films by light mineral oil in connection witli food uses. Anthrone was chosw as the most suitable reagent. M7hen carbohydrates are heated with anthront: in sulfuric acid, a green to blue-greer color is produced ( 2 ) . Morse (4) used this reaction for quantitative estimations of sucrose solutions; Morris (3) used it for the determination of glucc 138, glycogen, and lactose. Viles and Silverman (’7) applied the anthrone rcxgent to the analysis of starch and cellulose. They discussed the effect of heat on color development and in xoduced the idea of stopping the colcy reaction by immersing the reaction mixture in a cold water bath. Samsel and DeLap (6) determined methy1cc:llulose with anthrone. The foregoing investigators used the heat evolved when tho reagent in concentrated sulfuric tcid was mixed with aqueous carbohydrate solution
to furnish the heat required for the development of the blue-green color. Black ( I ) , who used the anthrone reagent to determine sodium carboxymethylcellulose, eliminated the heat of mixing, dissolved the solid sample in 60% sulfuric acid, added a solution of anthrone in a similar concentration of sulfuric acid, and heatcd the mixture for 15 minutes in a boiling water bath. Scott and Melvin (6) investigated the influence of reagent age, acid concentration, effect of temperature, and anthrone concentration on the analysis of glucose solutions. They recommended a 16-minute heating period a t goo c. Although the above method was satisfactory for the determination of Carbohydrates in aqueous solutions, the authors found it impossible to estimate small amounts of cellulose derivatives in the presence of oils, fats, and glycols because of color interference
