I. Determination of Palladium in Synthetic Solutions Foreign Ion Added, Mg. Palladium, y Mo Zr Rh Zn Cd Taken Found
Table
-
U
Ru
for solutions containing large amounts of alkali-insoluble materials. Such was found to be the case. Palladium is quantitatively extracted along with the excess reagent in the p H range of 1.0 to 2.0, no uxanium precipitation occurs, and EDTA serves to buffer the solution as well as to mask interfering elements. The excess reagent is scrubbed from the organic phase with dilute sodium hydroxide. I n making the initial p H adjustment, ammonium hydroxide is preferable to sodium hydroxide. With the latter, results are low and erratic. Similarly, low results were observed by Cheng when he used sodium hydroxide to make the solution basic. He attributed this to the adsorption of palladium on the precipitate formed. Since no precipitation occurs under the conditions described here, the reason for the low results is not apparent. Both sodium and ammonium hydroxide were tested as scrub solutions to remove excess reagent from the tol-
uene. Although no large differences in absorbance were noted, the use of 1N sodium hydroxide gave lower and more reproducible blanks. Excessively high blank values were found to be due t o decomposition of the reagent. Purification was effected by dissolving the reagent in ethyl alcohol and precipitating it with water.
€3 spectrophotometer in I-cni. cells at 370 mp. Determine the palladiiirn content from a calibration curve.
The molar absorptivity found by using the above procedure is 22,300. From absorbance data reported by Cheng, a molar absorptivity of 20,800 has been calculated. The color is stable for a t least 48 hours. The procedure has been tested on synthetic solutions containing known amounts of uranium, palladium, ruthenium, zirconium, and rhodium and was found to be satisfactory. The method has also been applied to the determinxtion of palladium in zinc and cadmium. Typical data on solutions containing knowii amounts of palladium are ~ h o w n in Tnblc 1.
RECOMMENDED PROCEDURE
LITERATURE CITED
Pipet a sample containing 5 t o 25 y of palladium into a 60-ml. separatory funnel and dilute to about 30 ml. with distilled water. Add 2 ml. of 301, EDTA solution. Adjust the p H to 1.0 to 2.0 with ammonium hydroxide or hydrochlorir acid. Add 0.1 ml. of 1% 2nitroso-I-naphthol and let stand for 10 minutes. Add 10.0 ml. of toluene. Extract for 1 minute, then discard the aqueoup phase. Add 10 ml. of 1N sodium hydroxide and shake. Transfer the toluene phase to a 15-ml. stoppered centrifuge cone and centrifuge. Measure the absorbance us. a reagent blank with a Beckman Model
(1) Alvarez, E. R., Anales direc. ycit. ofic. quim. nacl. (Buenos Aires) 2, 88
(1949).
(2) Cheng, K. I,., ANAL. CHEM.26, 1894 (1954).
L. E. Ross G . KESSER
E. T.KTTrERA Chemical Engineering Division Brgonne National Laboratory 9700 S. Cass Ave. Argonne, Ill.
Operated by The University of Chicago under Contract No. W-31-109-eng-38. Work performed under the auspicee of the U. S.Atomic Energy Commission.
Determination of Fluorine by Neutron Activation SIR: The method of shorb activation analysis has recently gained some very deserving attention. An activation procedure developed in this laboratory is thus presented for the determination of fluorine. An earlier procedure for fluorine employing the P-rays of F20 for counting 11-as reported by Atchison and Beamer [ANAL.C H E W 28, 237 (1956)]. The heart of the new method, which uses the F13 (n, CY) K16reaction, is a fast-transfer shuttle rabbit system permitting multiactivation runs with cumulative counting to improve both srnsitivity and statistical certainty of the analysis. The operation of the system is illustrated in Figure 1. The activations are carried out with the epicadmium neutron flux of a beryllium target irradiated with 2m.e.v. deuterons from a Van de Graaff accelerator (High Voltage Engineering Corp., Burlington, Mass.). The sample, packaged in a n aerodynamically-designed polyethylene rabbit running inside a 35 foot long polyethylene tube, inch in diameter, is inserted into the 1368
ANALYTICAL CHEMISTRY
system via the air lock located at the 3 X 3 inch NaI(T1) scintillation counter. Counter and air lock are inside a cubical lead shield of 3-inch wall thickness and 14-inch inside edge length. A camdriven timer activates simultaneously the solenoid air valves 1 and 2 and
Table 1.
transfers the rabbit into the irradiation position. The arrestor pin positions the rabbit reproducibly in front of the cadmium-covered neutron source. The solenoid valves are then deactivated and the airflow is stopped. A small air-leak prevents hack pressure that
Experimental Data of Some Fluorine Analyses by Fast Neutron Activation Fluorine, Mg. No. of
Samplr. Countsi 2162 LiF Standard $1 LiF 4140 3179 #2 LiF 1038 LiF Standard 1511 $3 SaCl(F), 517.1 mg. 3286 #4 Organic compound, 22 mg. 268 i 176 Background #5 H20,600 mg. 4 i 17 #6 NH4NOs,650 mg. 10 f 17 = Corrected for background. b Only statistical error considered. c Actual count of an empty rabbit. * Calculated for pure compound.
Cvclri
Foundb
10
IO 10
5 5 10 8 8 8
104*02 8 0 f 0 2
Present 5 45 105 8 0
5.45 T.9 f 0 . 2 8.610.1
..
..
..
8.0 8 7d
...
0
n
DETAIL 'A'
Figure 1. Pneumatic shuttle-rabbit system for multiexposure activation analysis
might dislocate the rabbit. Exactly 30 seconds later the timer opens valves 3 and 4 and the reversed air current transfers the rabbit back to the counting position, '/* inch from the center of the face of the scintillation counter. A spring-arrestor, a part of the air lock, positions the rabbit for counting. When 1.5 seconds have elapsed for the transfer, the timer turns on either a multichannel analyzer or a scaler for a prrdetermined counting time. The cycle is repeated once a minute until enough counts have been accumulated. The basis of this fluorine analysis ib the production of the 7.4-second N16 by the reaction Flg (n, a ) "6, which is induced by the fast neutron component of the available flux. The Q value foi this reaction can be calculated from the isotopic masses as -1.5 m.e.v. [lT7apstra, A. H., Physica XXI, 367 (1955)l. TJse of the penetrating 6.1-m.e.v. y-ratliation of NIB for counting permits the determination of fluorinc in thr prepvnce of most other elements.
I I
2
3
4
I
6
7
E N E R G Y (M.E.V.)
Figure 2. Gamma spectrum of a fluorine-containing N a C l sample collected into 70 channels of a multichannel analyzer
Oxygen also gives risc t o X16 by the for which the reaction 0 ' 6 (n, p ) "6. Q value is calculated as -9.6 m.e.v. However, because of the high Q value of this reaction, no interference of the fluorine determination is experienced with the flux available at this installation. This is seen from a n attempt to induce the ieaction in purifird water as reported in Table I. The sensitivity of the method, employing 10-cycle runs and the maximum permissible deuteron cmrent (36 pa.) for the production of neutrons lies at approximately 0.1 mg. of fluorine or I00 p.p.m. for 1-gram samples.
Table I gives some representative fluorine analyses as well as the observed count rates. Only pulses equivalent to 4.5 m.e.v. or more were used for the counts. A 30-pa. deuteron beam was used for the activations. Figure 2 gives the y-spectrum obtained from a fluorine-containing NaCl sample as well as the spectrum of its fluorine content. No interference due to the matrix material is experienced in the range above 4.5 m.e.v. OSWALDU. ANDERS
Radiochemistry Laboratory The Dow Chemical Ch. Midland. Mich.
Rapid Determination of 3-Chloropropene by Methoxymercuration Sin: The quantitative reaction of mcwuric acetate with certain ethylenic vompounds has been used for their detrrmination (1, 2, 6-7). Other ethylenic compounds react more slowly with mercuric acetate and their determinations are difficult. When mercuric acetate is added to unsaturated compounds such as methacrylic and acrylic esters in the presence of catalytic amounts of a strong acid such as perchloric, the reaction is greatly accelerated and these compounds can be determined by this procedure (3, 4) The chloropropenes react very dowly with mercuric acetate, but the author found that in the presence of small amounts of perchloric acid, the rate of reaction is greatly increased hfeth-
oxymercuration of 1-chloropropene, 3chloropropene, 2,3-dichloropropene, and 3-chloro-Zmethylpropene was studied in the presence of varying concentrations of perchloric acid in methanol medium under different conditions. Only 3-chloropropene3 which reacted quantitatively within 15 minutes a t room temperature, wva~ determined successfully. EXPERIMENTAL
Reagents. Mercuric acetate solution, approximately 0.1M in methanol containing ca. 0.005 t o 0.01M perchloric acid. Diphenylcarbaxone solution, in ethyl alcohol.
0.2%
Hydrochloric acid solution, 0.1N in butyl alcohol, standardized by the procedure (1) using thymol blue or diphenylcarbazone &s indicator. All reagents were analytical grade. Procedure. Standard solutions of the chloropropenes about 0.05 to 0.1M in methanol were accurately weighed into glass-stoppered bottles. Mercuric acetate solution was added t o the chloropropene solutions and allowed to stand a t room temperature for 15 minutes. After addition of 1 or 2 drops of diphenylcarbazone indicator to a reaction mixture, i t was titrated with standard hydrochloric acid in butyl alcohol. Reaction conditions were varied in all cases by increasing the concentraVOL 32, NO. 10, SEPTEMBER 1960
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