V O L U M E 27, NO. 8, A U G U S T 1 9 5 5
1.0
1293 T h e determinations show excellent adherence t o t h e BeerLambert law over t h e measurable concentration ranges (Figure 6) as well as great’ sensitivity. Colorimeter readings were also made, with t,he Klett-Summerson photoelectric colorimeter, with S o . 12 or Xo. 44 filters. These readings were likewise linear with concentration, and t h e measurable concentration ranges were about t,he same as with the Fpectrophotometer. Degree of Interference of Ethanolamine in the Ethylenimine Test. T h e presence of a relatively high concentration of ethanolamine in a n aqueous solution containing ethylenimine has b u t slight effect on t h e determination of the latter by the chloroform extraction method. Table I1 shows that the sensitivity of this method for ethanolamine is b u t 1/100th that of the test for ethylenimine.
-
k3 B
p U
PARTS PER MILLION
Figure 6.
Table 11.
Sensitivity curves for amine determinations
Degree of Interference of Ethanolaniine in Ethylenimine Testa
Solution Concn., P . P . X Reagent blank Ethyleniniine 1 Ethanolaniine 6 Ethanolamine 10 Ethanolamine 24 1 to 6 Ethylenimine-ethanolamine 1 t o 10 Ethylenimine-ethanolamine Ethylenimine-ethanolamine 1 t o 24 Chloroform extraction method.
Absorbance a t 420 m& (.4v.) 0 015 0 491 0 025 0 048 0 062 0 521 0 541 0 548
small errors in timing nould not introduce appreciable errors in the absorbance readings. Sensitivity and Adherence to the Beer-Lambert Law. T h e sensitivities of the analyses are 0.40 for ethylenimine, 0.19 for n-butylamine, and 0.048 for ethanolamine, n here sensitivity is defined as Absorbance of sample - iibsorbance of reagent blank .~ part. per million of amine
ACKNOWLEDGiCIENT
T h e authors wish t,o thank Reuben Proper of this branch for carrying out t’hesyntheses of S-but>-lethylenimineand potaspiurn 1,2-naphthoquinone-4-sulfonate. LITERATURE CITED
(1) Danielson, I. S..J . B i d . Chem., 101, 505-22 (1933). (2) Drake, T. L., “Organic Syntheses,” 1-01, 21, p. 91, Wiley, New York, 1941. (3) Elderfield, R. C . , J . 0,s. Chem., 14, 605-37 (1949). (4) Folin, O., J . B i d . Chem., 51, 377-91 (1922). (5) Lange, -4.L., “Handbook of Chemistry,” 6th ed., p. 1102, Handbook Publishers, Sandusky, Ohio, 1946. (6) Letonoff, T. V., and Reinhold, J. G., Am. J . M e d . Sci., 188, 142 (1934). (7) Schmidt, E. G., ISD. ENG.CHEY.,ASAL. ED., 11, 99--100 (1939). (8) Schmidt, E. G., J . Bid. Chena., 122,757 (1938). (9) Shirley, D. A , “Preparation of Organic Intermediates,” p. 153, Wiley, S e w York, 1951. (10) Sullivan, hf. X., and Hess, W. C., Public Health R e p t s . ( C 7 . S , ) , 44,1421-8,1699-608 (1929). RECEIVED for review Se~iteinber2, 1934. .-iccepted .\pril 2, 195.5.
Colorimetric Determination of the Perchlorate Ion WOLF BODENHEIMER’ and HANNAH WEILER A n a l y t i c a l Laboratory, Scientific Department, M i n i s t r y o f Defence, Jerusalem, Israel
The perchlorate ion gives a precipitate with the cupric tetrapyridine cation. The ensuing decrease in the color intensity of solutions of cupric tetrapyridine ion can be measured spectrophotometrically and used for the quantitative determination of the perchlorate ion. The method has also been applied to the determination of the perchlorate ion in organic perchlorates.
C
UPRIC tetrapj-ridine perchlorate, studied aiid characterized
by Weinland, Effinger, and Beck ( a ) ,had been suggested by Shead and Bailey ( 1 ) as a means of identifying the perchlorate ion. T h e object of the present investigation n-as t o use the cupric tetrapyridine complex for the quantitative estimation of the same ion. The solubility of t h e cupric tetrapyridine perchlorate in water, although slight. excludes a gravimetric method. However, the solutions of salts of t h e cupric tetrapyridine complex in aqueous pyridine show an intense blue color, the intensity of which decreases as part of the complex is precipitated as per1 Present address, Geological Institute, Israel hlinistry of Development and Hebrew University, Jerusaleni, Israel.
chlorate. This fact makes the colorimetric determination of perchlorate possible.
INORGiUIC PERCHLORiTES Using the conditions described b - Shead and Bailel- ( 1 ) a solution of cupric tetrapyridine nitrate in a mixture of water and pvridine IT as prepared; varying quantities of ammonium perchlorate were added to equal volumes of this solution and after crystallization of the cupric tetrapyridine perchlorate, the absorbance of the solutions -A-asmeasured. -1curve v-as thus obtained, showing the absorbance of a solution of the complex as a function of the amount of perchlorate added. T h e results obtained n i t h this curve, hom-ever. nere satisfactory only as long as no ions other than perchlorate and nitrate were present. Quantities of chlorate, chloride, or sulfate, of the same order of magnitude as the amount of perchlorate present. affected the color or gave precipitates. As i t is often necessary t o determine the perchlorate in t h e presence of these interfering ions, conditions rrere sought under which their influence was suppressed. T h e folloir-ing four points nere studied.
-
ANALYTICAL CHEMISTRY
1294 Table I.
Influence of \.arious Salts on Absorbance of Solutions of Cupric Tetrapyridine Sitrate ~~
XR?SO$
Absorbance of solutions Containing 0.2 m g . h l . of perchlorate Containing 0.4 nig./nil. of perchlorate
8
20
0 673 0.481
0 6iii
0.040 0.498
...
Table IJ. Influence of Temperature on Absorbance of Cupric Tetrapj-ridine Kitrate Solution Temp.. 0
c.
Absorbanre
11
71
0.279
0 2Gi
25
30
35
40
0.263 0.255 0 . 2 4 3 0.232
Salts Added. l I g . / l I l . HSOa, 20 20
KCLo:i__
Xone
45
50
0.222
0.17:
Effect of Pyridine Concentration. The addition of more pyridine to the solution prevented the formation of precipitates by sulfates or cthlorides, and deepened the color of the cuprir tetrapyridine complex. Figure 1 shows the variation of the absorbance of a solution of the coniples as a function of the quantity of pyridine added. .it eqiial volumes of water and p>-ridine, the maximum absorbance of the complex is practically reached. Further additions of pyridine increase the soluhility of the rupric tetrapJ-ridine perchlorate and must, therefore. be avoided. Effect of Various Anions on Color of Complex. The absorbance of solutions containing varying quantities of sodium chloride, sodium sulfate. potnssium bromide, or potassium nitrate \Tar; measured (Figure 2'1. Sodium chloride solutiom give the deepePt color n-ith the cupric tetrapyridine complex, bromide has a smaller influence. and sulfate and nitrate do not change the color a t all. JIoreover. in the presence of a high concentration of sodium chloride the effect of other anions (chlorates. phosphates, nitrates, bromides, etc.) on the color of the solution was almost entirely suppressed (Tables I and 111). Effect of Various Cations. The presenre of sodium, p o t a s i u m , ammonium ions, or of alkaline earth metals in concentrations u p t o 10 mg. per nil. has no influence. Higher concentrations affect the extinction slightly (Table I ) . Other metals (silver, manganese, iron, aluminum. zinc). on the other hand, were found t o form either compleses Kith pyridine or precipitates of the hydroxides; they have, therefore. t o be removed before determination of the perchlorate. Effect of Temperature. The effect of changcs of temperature on the color of the solution is shown in Table 11. I n the range between 10" and 25' C. there is very little change in the absorbance of the solution.
8
o:&
0.642 0.501
0.672 0 . x ~
__--
~~
XHICL.
.\IqCI?. 2i)
CaCl?, 0 '
BaCI?.
20
0.682 0.508
0.681 0.501
o:Sii
o'iii
20
These solutions are left for 48 hours to crystallize (for concentrations u p t o 0.5 mg. per ml. 24 hours are sufficient). T h e solutions are filtered and t h e absorbances of the filtrates a r e measured in a Beckman DC spectrophotometer a t 6350 A. T h e results are plotted against the concentrations of perchlorate ion, as shown in Figure 3 . Analysis of Sample. A solution is prepared from the sample as described in the preparation of the calibration curve ( 2 ml. of solution A, 20 ml. of solution B, a weighed quantity of the unk n o m sample, and water t o 25 ml.). After 48 hours, the ahsorbance of the supernatnnt solution is measured, and the concentration of perchlorate is reid from the cslibration curve. (For tech, results can be obtained after a few hours if the solution is shaken mechanically. The calibration curve has then to be prepared under the changed conditions. T h e accuracy of the method n-ill be reduced, but n-ill still suffice in many cases.) RESCLTS
In Table I11 results are given of determinations carried out both in the absence and in the presence of other salts. The accuracy of the method is within 0.01 mg. per ml. At concentrations of 0.5 t o 1.2 mg. of perchlorate per nil.. the error lies between 1 and 2%. If the concentration of other ions in the soliltion rises above 10
PROCEDURE
As a result of these studies the following method waq adopted. Thrce stock solutions are required. 0 5 10 Solution A. Aisolution prepared by dissolving about 25 grams Pyridine A d d e d , ML/5 MI. Solution of cupric nitrate trlhydrate in water, adding 540 ml. of pyridine, Absorbance and making up x i t h nxter to 1 liter. (Kept in a brown bottle, Figure 1. Change in color intensity of cupric this solution did not change its optical properties for a t least 2 tetraprridine nitrate solution on addition of years.) pyridine Solution B. -in aqueouc solution of 20 grams of sodium chloride per 100 ml. Solution C. -1 solution containing 58.75 mg. of ammonium perchlorate per nil. (50 nig. of perchlorate anion per ml.). Preparation of Calibration Curve. &% dozen solutions are prepared containing: 2 nil. of solution A ; 20 ml. of solution B; varying quanti0 9.0 4.0 6.0 8.0 10.0 19.0 ties of solution C (increasing gradually the Figure 2. Change in color intensity of cupric tetrapyidine nitrate solution on perchlorate c m t e n t i n addition of anions the final Polutions from zero to 1.6 nig. per nil.); A . NaCladded C. Na2SOI added and watcr t o 2.5 nil. B . KBradded D . KNOa added
V O L U M E 2 7 , NO. 8, A U G U S T 1 9 5 5
1295
1.o
or more, \%hich is not sufficient for organic analyses. For solutions saturated with sodium chloride the calibration curve is practicallv a straight line for much lo\ver concentrations. I t is thus possible to determine quantities of perchlorate even helon100 y per ml. with an accuracjwithin &5 -1.
Y
:" 0.5
4
2
2 0 1.o 1.5 Perchlorate Added, Mg./MI.
0.5
0
Figure 3.
2.5
2.0
PROCEDURE
Preparation of Calibration Curve. Solutions of potassium perchlorate are prepared containing 0.0, 1.0, 2.5, 5.0, 7 . 5 , 10.0, 12.5. 15.0, 20.0, and 50.0 mg. of perchlorate ion, respectively, 2 ml. of stock solution A. and water to 25 ml. These solutions are saturated with an eicess of dry sodium chloride of analytical grade. They are t,hen shaken vigorously, left t o crystallize overnight, and filtered through dry filter paper. T h e absorbance of the filtrates is measured in a Klett-Summerson colorimeter with filter 66 ( h n s m i t t a n c e range from 6400 to 7000 L4,),and is plotted against the concentration of the perchlorate ion (Figure 4). Analysis of Sample. T h e sample is dissolved in water to a concentration of betn-een 50 and 600 y of perchlorate ion per ml. A volume of 2 ml. of stock solution A is added, and the solution is made up to 25 ml. If only very small quantities of sample are available, this volume can be correspondingly smaller, the only limit being that required for the colorimetric measurement. This solution is shaken with a n escess of dry sodium chloride, kept overnight, and filtered. T h e absorbance of the filtrate is measured and the perchlorate ion content is read from the calibration curve.
Calibration curve for inorganic perchlorates
0.400
0.300 U W
Z
Q
p 0.200 0
2 Q
0.100
0
Figure 4. Calibration
curie
1 .o
0.8
0.2 0.4 0.6 Perchlorate Added, Ms./MI.
0
RESULTS
for organic perchlorates
mg. per ml.. in some cases slight deviations occur nhich, however. do not cause an erior gretater than 0.03 mg. per ml. If very high concentrations of another ion are prespnt, it is advisable to prepare a calibration ciirve cor1 cspondirig to these conditions.
ORG.41UIC PERCHLO RriTES Owing to their l o eoluhility ~ in \Tater. organic perchlorates are
often used for the separation and purification of organic bases. R7hilr the comblistion :insl>-sis of thrse perchlorates is not practical, bemuse of their tentietic>. to explosive decomposition. the colorimetric method desrrihctl above ni:dies it possible to determine the perchlornte ion tlirec>tlj-.even in w r y dilute solutions of the salts. Under the conditions tlrwrihed. optimal accuracy is ohtnined only with quantities of ahout 0.12 mg. of perchlorate ion per nil.
The percentage of perchlorate ion contained in the organic perchlorate is readily obtained from the perchlorate contrnt of the solution. T h e molecular weight of the organic compound can be derived from this drtermination. Table IV shone results ohtained b\ this method. ACKYOWLEnGME\T
T h e autbo1.s \\.ish to thank Felix Bergmann for the suggestion to extend their method to organic perchlorates, and E. D. Bergmann for the interest shomn in this Tvork. This investigation has h e n carried out under the auspices of the Israel M i ~ ~ i s t of r y Defence. LITERATURE CITED
(1) Shead, d.C., and Bailey, P. S., M i k r o c h e m i e , 33, 1 (1947). ( 2 ) Weinland, R., Effinger, K., and Beck, V., Arch. Pharm., 265, 352
(1927). RECEIVED for review September 16, 1954. Accepted April 1 2 , 1955.
Table 111. Results Obtained Using Calibration Curve (Figure 3)
Perchlorate, mg./nil. Added Found
KBr, 8
Sone
SaZSOA, 8
KCIOZ, 8
0.48 0.47
0 . d2 0.52
0 56 0.57
0.60 0.60
Salt Present Besides NaC1, Mg./lII. KSOa, PiHaCI, BaCI?, 8 8 8
0.68 0.69
0.72 0.73
0.76 0.76
BImClr, "8
KBr, 8
None
0.84 0.85
0.88 0.89
0.92 0 90
1 .oo 0 98
Table IV. Determination of Perchlorate Ion in Various Organic Perchlorates 70of Perchlorate Ion hIolecular Substance Benzoylcholine perchlorate Brucine perchlorate Quinaldine perchlorate Trirnethylbutylammoniuni perchlorate Trimethylheptylarninonium perchlorate Trirnethyloctylainrnoniuni perchlorate Trirnethyldodecylanimoniuin perchlorate
Found 32.2, 32.4,31.9, 32.4, 3 2 . 3 19.7, 2 0 . 3 4 2 . 4 , 41.5, 4 2 . 0 45.8, 46.6 39.3, 38.1, 38.6 36.1, 37.4. 37.3 30.9, 30.6
Theoretical 32.4 20.1 40.4 46.2 38.8 36 6 30.4
.______
CaClz, 8
Found 308, 307. 312, 307, 308 502, 490 236. 240, 217 217, 214 254, 2 6 2 . 258 276, 266, 267 322, 325
Weight Theoretical 307 495 243,7 213 5 257.5 271.5 328
