in samples containing 0.5 gram of Cd was, 114,000 liters mole-’ crn.-’
Possible interferences were deduced from the extraction data for bromides
DISCUSSION
The HBr concentration must be at least 1M for complete extraction of TI(1II) into isopropyl ether in the presence of large amounts of zinc (Figure 1). Above 3M HBr, interference from small amounts of entimony becomes serious (3). Therefore, within the range of 1 to 3114 HBr, extraction of Tl(II1) is complete and free from antimony interference. Concentrations of other reagents, such as the ceric sulfate solution or the rhodamine B-acid solution are not particularly critical (9). Convenient values were selected for the procedure. No oxidizing agent is required to effect solution of zinc and cadmium samples if both sulfuric and h y d r e bromic acids are used. When this is done, thallium remains in the Tl(I) state and R small amount of ceric sulfate must be added to oxidize it to Tl(II1). Contrary to previous reports, a small excess of ceric ion need not be destroyed because it does not appear to cause any difficulty in the rhodamine I3 extraction.
Table 1.
Interference of Diverse Ions
[No interference ia indicated if iom pro. duced a color change e uivdent to lege samples (6% than 1 pg. on 20-pg. relative error)] Effect Ion Cr(VI) Cr(II1)
Amount 10 mg. 10 mg.
As( 111) cu(111 Sn( IV) AI(II1) Ge(IV) Fe(II1) In(1II) Mn(111)
10 pg. 100 mg. 100 mg. 500 pg. 100 Pg. 10 mg. 100 mg. 60
Source
on TI
Detn. LOW
(reduced)
A&O.
MGl
SnCl, Metal Metal
(reduced) Pb(IV) 100mg. Metal l m g . Metal 8b(V) 100 pg. KNO, NO#NO#“0, Large excesa’ Au(II1) 100 pg. Metal HP(IIi 100pg. G d I I ) 100pg. *The sample waa diaeolved acid.
zea
None None None None None None None None None None None None Color fadm High High High in nitria
in ethyl ether and for rhodamine B complexes (1). Table I lists the ions investigated in the interference study. Serious interference occurred with strong oxidizing agents and with Au(III), Hg(II), and Ga(II1). A reasonable separation from these ions was obtained by reducing thallium with hydrazine in acid solution and extracting the Tl(1) with dithizone in CClr (8). The thallium then was determined by the rhodamine B procedure following evaporation of the organic phase and wet oxidation of the remaining organic matter. LITERATURE CITED
H.,Freieer, H., “Solvent Extraction in Analytical Chemiatry,” pp. 131, 164, Wiley, New York,
(1) Morrieon, G.
1957. (2) Sandell, E. B.
“Colorimetrio D: termination of $race8 of Metals 3rd ed., p. 830, Interacience, New York,
1969. (3) Van Amen,
R.E., Hollibsu h, F. D., Kanzelmeyer, J. H., ANAL. &BY. 31,
1783-5 (1969). (4) Woolley, J. F., Analyst 83, 477-9 (1958).
R.E. VANAMAU J. H. KANEIIILIKEE~~~R Zinc Smelting Diviaion St. J m p h Lead CO. Monaca, Pa.
Improved Gas Chromatographic Analysis for Fuel Dilution and Volatile Contaminants SIR: 111 1959 a sensitive, precise, and accurate determination for fuel dilution in lubricating oils wm reported (3). With advances in gas chromatography it is now possible to perform improved and more versatile diluent analyses with greatly simplified e q u i p ment and procedures (4). Diluent concentrations in weight per unit volume are obtained by comparing peak area for diluent with that for internal standard. The standard is blended with the sample in 2% concentration prior to testing. Analyses may be made without internal standard by using the backflush area for oil. Diluent concentrations calculated from calibrated backflush areas are in weight per cent. Fluids with vapor pressures es low BB a few millimeters of Hg at 240’ C., may be treated this way. Heavier oils containing molecular weights >500, which may leave fractions on the column, are better handled by the internal standard method. Sample size depends on the precision desired, with the minimum being less than 10 pl. This compares with 25 to 50 ml. required for leas accurate fuel dilution tests by distillation (1-4). Analyses have been made from 0.01 to 5OoJ, diluent with a maximum
error of h15% of the amount present. Among other advantages, analyses are rapid and give an indication of diluent composition (3, 4). lj-igure 1 shows a typical recorder trace obtained with the improved procedure for fuel dilution analysis. The following conditions are used for dilution tests: The column is 12
feet of i/Cinch 0.d. copper refrigeration tubing. It is packed with 42-60 meahsise Johns-Manville (2-22 insulating brick, which is coated with 28% by weight of esphalt. The asphalt is safaniYa crude, which has been nitrogen blown at 320’ C. for 24 hours. The asphalt is placed on the brick by evaporation of a benzene solution. Other packings will suffice. The detectors
DILMNT
7
25
1 IYI.UIWvRI
Figure 1.
Typical chromatogram for fuel dilution analysis VOL. 33, NO. 8, JULY 1961
1129
are matched thermistors, 8000-ohm nominal, maintained at 10 volts in connection with a conventional 0 to 1 mv. stripchart recorder. The helium carrier gas is adjusted to inlet pressures near 15 p.s.i. t,o give a flow rate of 35 ml. er minute as measured by a bureb-soap ubble meter. Test temperatures are: injection block, 310’ c.;column, 240’ c. Other conditions, such as sample handling and blending, are as previously described (9,4).
(2) Ibid., Appendix I, p. 1076,1958.
ACKNOWLEDGMENT
The authors express appreciation to K. E. Thompson for help in develop ment of the method.
E
LITERATURE CITED
(3) Porter, R. S., Johnson, J. F., ANAL. CHEM, J1, 866 (1959). (4) Porter, R. S., Johnson, J. F., Petrol. Refiner 39, No.6,193(19130).
ROGERS. PORTER JULIAN F. JOHNSON California Research Corp. Richmond, Calif.
sot. Testing ~ ~ b ~pmec i ~ h ,
(1)
delphia, Pa., “ASTM Standards on Petroleum Produc&,” P. 170, Method D 322-58T, 1959.
A Spectrophotometric Determination of Rhenium SIR: In studies concerning rhenium in this laboratory, it was necessary to determine rhenium concentrations in standard solutions. Many of the known methods for the colorimetric determination of ihenium require special procedures such as solvent extraction to stabilize the color (1,6,7,9), A quick and reliable method was sought which would not involve any of these special procedures. The basis of the colorimetric procedure described below was the qualitative scheme involving 1henium and several chemically similar elements recently reported by Fadhil, Magee, and Wilson (4). Rhenium was identified by the orange color produced on treating perrhenate ion with dimethylglyoxime(DMG) and stannous chloridehydrochloric acid solutions.
adjusted to 10 ml. The absorbance of the deep orange-colored solution was measured immediately, and then at time intervals of 25 minutes, 2 houm, and 49.5 hours after preparation. The results shown in Figure 1 demonstrate that the color is stable for at least 2 hours after preparation, which precludes the use of solvent extraction for stabilization. To several solutions, each c o n t a e g
153 p.p.m. of Re per ml., v a r q g
amounts of concentrated hydroch 0110 acid were added, a n d , the color WBB developed as described previously. Absorbance meaaurements were made at 620mp after 30 minutes had elapsed. The p H dependence of the color is illustrated by the results given in Table
APPARATUS A N D REAGENTS
-
21
A Leite-Photrometer (No. 21942) waa used for the absorbance measurements and l-cm. square quartz cells were employed to contain the solution. The solutions used were: aqueous solution of potassium perrhenate, ethyl alcohol saturated with DMG, and a 2 M solution of stannous chloride in 10M hydrochloric acid.
20-
EXPERIMENTAL
13-
Stability of the orange color was investigated in the following manner: One milliliter of DMG solution was added to a perrhenate solution (766.5 p.p.m. of Re) in a 10-ml. volumetric ftask, followed by 0.5 ml. of stannous chloride solution, and the volume waa
19-
2 min. allar preparation 25 min. ofler prenaration
18-
2 hr. after preparation 49 S hr. alter preparation
1 7 -
16-
1 5 1 4 -
2
2:1 1 -
1 2 -
I O -
09-
06-
Table 1.
pH Dependence
Absorbance Color PH 0.302 1.620 Orange -0.230 1.409 Orange with green hue -0.462 0.883 Orange with green -0.612 -0.724
-0.886 -1.004 1130
tint
0.568 0.310 0.154 0.102
Orange-green Green with orange
0 5 04-
030201
0
I
400
tint
Yellow-green Light green
ANALYTICAL CHEMISTRY
460
I
520
I
580
I
I
640
mP
Figure 1. with time
Variation of absorbance
I. The pH of the first sample, which had no exceea acid, is on an approximate plateau and thus is at what would be considered an optimum pH. An even higher p H would be desirable, but solutions of stannous chloride must have 5 certain acid concentration to prevent hydrolysis. Several standard solutions of rhenium were prepared and the orange color was develo ed by adding 1 ml. of DMG and 0.5 of stannous chloride solutions, and adjusting the volume to 10 ml. After standing for 30 minutes, the absorption waa measured at 520 mp. To test the validity and reproducibility of this method, two sets of standard samples of varying rhenium concentrations were prepared and the absorbance waa measured after the orange color had been developed in each one.
mf
The results are summarized in Table I1 and Figure 2. The average error was 5%. Above 260 pap.m.of rhenium, because of the extremely dark orange coloration, i t waa very difficult to read the Photrometer absorbance scale accurately. Below 1 p.p.m. of rhenium, a white precipitate formed and anomalous results occurred. Decreasing the DMG or stannous chloride concentrations did not alleviate this trouble. Although interfering ions were not present in the solutions meaaured, some work was performed in this area with the idea that this method could be developed into a general procedure in the future. Copper does not interfere even
Table II. Percentage Error P.P.M. Re Added % Error 1.012 8.4 6.11 13.7 20.44 7.0 30.44 1.8 51.1 2.0 3.5 75.65 1.2 102 2 127.75 6.5 204.4 4.6 204.4 2.1 I
