V O L U M E 2 4 , NO. 3, M A R C H 1 9 5 2
583
(8) Benedetti-Pichler, A . A,, “Microtechnique of Inorganic AnaIysis,” pp. 238-40, 257, Kew York, John Wiley& Sons, 1942. (9) Clemo, G. R., and McQuillen, 1., J . C‘hem. Sac., 1935,1220. (10) Jones, G., and Ferrell, E., Ihid.. 1939,325. (11) Jones, G., and Stauffer, R. E., J . A m Chem. SOC.,62,335 (1940). (12) Kirk. P. L., “Quantitative Ultramioroanalysis,” pp. 18, 22, 23, 24, 25, 26, 296, New York, John Wiley & Sons, 1950. (I:i) Levy, M., 2. physiol. Chem., 240, 33 (1936).
LIika, J., “Die exakten Methoden der Mkromassanalyse,” 32, Stuttgart, F. Enke, 1939. (15) Moore, S., and Stein, W.H., J . B i d Chenz., 176, 367 (1948). (14)
p.
c.
L., Willits, C. O., Ricciuti, C., and Connelly’, J. ANAL.CHEM.,23, 911 (1961).
(16) Ogg,
A,,
(17) Qstwald-Luther, “Hand- und Hilfsbuch zur Ausfuhrung physikochemischer Messungen,” pp. 225-41, Leipsig, c. Diucker, 1931. (18) Thomas, A. H., Co., 1950 edition, “.Laboratory Apparatus and Reagents,” Trenner diluting pipet, No. 3394, p. 328, ultramicropipet, KO.8206-K, p. 1022. (19) Trenner, Simeon, U. S. Patent 1,678,540 (July 24, 1928). R E C K I V Efor D review
i i u g u s t 9, 1951.
.Accepted Xovember 3 , 1951.
Determination of Cyanides in Refinery Waste Water MAXEY BROOKE Phillips Oil Co., Sweeny, Tex.
lHE accurate determination of t i m e quantities of cyanides in
Iwaste water has long been a pro1)lem facing the water chemist.
The particular problem under investigation concerned the lormation of ammonium cyanide during the catalytic cracking of iiitrogen-containing gas oils. These cyanides are subsequently Lvashed outof the gasolineand find their m y into the refinery waste $tieam. The quantity of cyanides produced is small, but state sanitary regulations prohibit the introduction of even this minute quantity into the streams that are customarily used for disposal of refinery waste. Most procedures, including that outlined in standard methods of the American Public Health Association ( I ) , call for the distillation of hydrocyanic acid froni the acidified sample. When xaters containing minute quantities of cyanides are distilled, it is very difficult to obtain reproducible results. Furthermore, there arc but few reactions involving cyanides which give colored and/or insoluble products. Cooper (2) found that the palladium complex of dimethylglyosinie was soluble in aqueous alkali hydroxide. Feigl and Feigl (3) found that such a solution would react with ryanidr ions. [PdD?]--
+ 4 C S - + [Pd(CX)4]-- + 2 D -
corresponding to demasking of the tliniethylglyoxinie~which can react Jvith nickel to produce the familiar red salt. Such a method \vas proposed as specific for cyanides, but when checked in this laboratory, it was found to be sensitive only to 3 p.p.m. This is not sufficiently sensitive for use by a water chemist,. .4number of other dioximes were examined in an attempt to find one that would give greater sensitivity. or-Furiltiioxime was selected as the best of those tested.
Standard Cyanide Solution. Dissolve 1 gram of pot:tssium ryaiiide in 1 liter of distilled water. Determine the esact strength by titration with 0.1 S silver nitrate (1 ml. of 0.1 :V AgK(lI = 2.6 mg. of CS). Dilute with distilled water so that 1.0 ml. contains 0.1 mg. of cyanide. Sodium acetate, saturated solution in water. Nickclous nitrate, 5% nickelous nitrate hexahydrate in distilled water . PROCEDURE
Place 100 nil. of the clarified water to be tested in a Kessler tube. If the water contains more than 3 p.p.m. of cyanides, dilute it. Prepare a series of standard tubes containing 0, 0.5, 1.0, 1.5, 2.0, 2.5, and 3.0 ml. of standard cyanide solution diluted to 100 nil. One milliliter of cyanide solution is equivalent t o 1 p. p. ni. To each tube add 5 ml. of pallaclium-or-furildioxime solution and mix. Add 3 ml. of sodium acetate solution and 0.5 ml. of nickelous nitrate solution and mis. The color develops almost immediately.
c s , P.P.M.
The uiikno\vn should he compared Tvith the standards within 10 minutes. The color begins to fade slowl>- after that time and after 30 minutes the fading is rapid. I t is not practical to measure the rate of fading. The lower limit of identification is 0.5 p.p.ni. I n the range of 0 to 3 p,p.ni. it is easy to differentiate between two solutions differing by 0.5 p.p.ni., and thus possible to interpolate with a precision of 0.25 p.p.in. INTERFERENCES
AI’I’A R ATU S
This method is not considered adaptable to spectrophotometric measurement. The reaction is not a true color change, but the formation of a red colloidal precipitate viewed against a green I)ackground. Because of difficult>- in controlling particle size, which tends to increase with increasing cyanide concentration, turbidimetric methods were not used. J-isual comparison is mare simple and of sufficient accuracy.
Of the ariioiis that are nornially found in refinery waste Fvater, none except sulfides interferes with the test. A series of Sessler tubes each containing 1 ml. of standard cyanide solution was prepared. One tube n-as filled to the mark with distilled LT-ater, anot,her with laboratory tap water, and the others with solutions containing the following salts: P.P.AI. 1.
2.
RE4GENTS
Palladium-or-Furildioxime Reagent. Dissolve 0.01 gram of 01furildioxime (Eastman Kodak Co. S o . 3308) in 25 ml. of 95% ethyl alcohol, and add 0.3 ml. of 5% palladium chloride. Filter the precipitate by suction, wash with alcohol, and dissolve in 5y0 potassium hydroxide. This solution is unstable and should he freshly prepared daily.
Color
3. 4. 5.
6. I.
Sodium chloride Sodium carbonate Disodium phosphate Sodium nitrate Potassium thiocyanate Sodium sulfate Free chlorine
Chlorides Carbonates Phosphates Kitrates Thiocyanate Sulfates Chlorine
500 250 30 1000 1000 50 2
KO difference in color development could be detected. However, by increasing the phosphate concentration to 3000 p.p.m., the color was reduced an equivalent of 1 p.p.m. of cyanide.
584
ANALYTICAL CHEMISTRY
When tests were repeated in the absence of cyanides, none of the solutions listed developed any color. However, a solution containing 1000 p.p.m. of mixed phenols, such as can be recovered from gasoline caustic washes, developed a color equivalent to 1 p.p.m. of cyanide. Sulfides, which are usually present in refinery waste waters, will form a black precipitate with the nickel, completely masking any color development made by cyanides. The sulfides can be removed satisfactorily by treating the neutral or slightly acid waste water with cadmium nitrate to precipitate the yellow cadmium sulfide, which can be filtered. The results must then be corrected for the amount of acid and cadmium sulfide solution added. Sulfide concentrations up to 100 p.p.m. have been removed by this method. Higher concentrations have not been encountered. Obviously cations such as iron, aluminum, and magnesium, which give hydroxide precipitates in alkaline solutions, will interfere with the test. Hydroxide formation of some of the heavy metals can be suppressed by complexing with citric or tartaric acid, but complete removal by ion exchange is preferable. Amberlite 100-H, a laboratory grade resin, and Catex 12, a commercial carbonaceous exchanger, have been used satisfactorily. Two techniques have been employed. The waste water can be percolated through a column packed with the ion exchange material in the sodium form. The first 100 ml. collected are discarded and the second 100 ml. are used for test purposes. A column 1 inch (2.5 cm.) in diameter and 12 inches high can be used for 25 to 100 determinations and can be regenerated by contacting the material with a 5% salt solution for 15 minutes and washing with distilled mater until free of chlorides. If only a few samples are to be run, the batch method may be preferable. To 150 to 200 nil. of waste water in an Erlenmeyer flask about 25 grams of sodium ion exchange material are added and the solution is sxTirled gently for 5 minutes. Then 100 ml. of the water are decanted and the test is continued.
Turbid solutions must be clarified before making the test. The suspended solids in refinery waste water are mostly colloittal and cannot be filtered. For most analytical tests they are iemoved by a filter aid such as activated carbon or Attapulgus clriy. In other cases a heavy metal and a hydroxide are added. The heavy metal hydroxide precipitates and removes the suspended solids on settling. These methods all removed a portion of the cyanides. Magnesium hydroxide had a particular affinity for cyanides, completely adsorbing them from the dilute solutions tested. It was found, however, that a pulp of ashless filter paper (Whatman No. 40) would clarify the waste waters without afferting the cyanide concentration. To 200 ml. of waste water in u graduate cylinder, about 1 gram of filter pulp was added. The cylinder was shaken and the pulp allowed to settle. The supernatant liquid was decanted for further treatment. CONCLUSIONS
A colorimetric method for the determination of cyanidea has been developed, which does not require preliminary distillation and is sensitive in the range of 0.5 to 3 p.p.m. of cyanide. 9 1 though it was developed piimarily for use on refinery wastc waters containing alkaline cyanides, the method could be applied to other problems requiring the determination of trace quantities of cyanides. Soluble cyanides other than alkaline cyanides offer no problem, as they can be converted to the alkali form by an ioii wchange method. LITERATURE CITED
(1) American Public Health Association, K’ew York, “Standard Methods for the Examination of Water and Sewage,” 9th ed., p. 90, 1946. (2) Cooper, R. A., J. Chem. M e t . Mining SOC.S. Africa, 25, 296
(1925). (3) Feigl, F., and Feigl, H. E., Anal. Chim. Acta, 3, 300 (1949).
RECEIVED.4pril 4, 1951. .iooepted October 5 , 1951.
Direct Determination of Oxygen in Organic Compounds by Elementary Isotopic Analysis A. V. GROSSE AND A. D. KIRSHENBAUM Research Znstitute of Temple University, Philadelphia, Pa.
HE! development of am accurate method for the determiT nation of oxygen in organic compounds has become of increasing importance. A good direct method would have
The per cent oxygen, in a sample of weight a, is calculated as follows :
%O=
b X ( m - n) x 100
obvious advantages over the usual procedure of reporting the amount of oxygen in a compound as the difference between 100% and the percentage sum of all-over determinations. Recently a number of publications have appeared on the direct determination of oxygen in organic compounds by the “classical” methods of quantitative analysis (1-5, 8-10, 12,13). The authors reported (7) a n isotopic method for determining oxygen, which in principle does not require any quantitative separation of oxygen compounds but nevertheless is potentially more accurate than any of the classical procedures. At that time heavy oxygen was available only in 1.2 atom % concentration. Heavy oxygen is now available in the concentration range of 5 to 10 atom %, and the ratio of two isotopes in the low mass range can now be measured precisely t o the sixth decimal place by the Nier-Consolidated mass spectrometer (11). These advances have greatly increased the accuracy obtainable, which is demonstrated by the results shown in Table I.
The liquid samples were distilled into the platinum tube as described previously ( 7 ) . Solid samples were weighed in a small platinum boat inserted into the platinum tube and the latter was sealed to the system.
PRINCIPLE OF METHOD AND APPARATUS
RESULTS
The method and apparatus have been described in detail ( 6 ) . A photograph of the equipment now used a t the Research Institute is shown in Figure 1 .
The results are given in Table I. The first two analyses were obtained with a standard Consolidated instrument, while for the rest the more precise Nier-
where b is the weight of added oxygen, containing m atom % excess 0 1 8 , and n is the atom per cent excess of OI8 in the mixture after high temperature equilibration in a platinum tube. SUBSTANCESANALYZED
Acetic Acid. A heart cut of pure glacial acetic acid was used. Both the refractive index and melting point agreed with the best literature values. Sucrose, C.P. Baker’s analyzed grade, dried in a desiccator. Benzoic Acid, C.P. Baker’s analyzed grade, melting a t 122.8’ C . 1-Naphthol, C.P. crystals, melting point 95.5” C. METHOD O F INTRODUCING SAMPLES
