ANALYTICAL CHEMISTRY
1246 Interhcial Angles (Polar). 101 h 101 = 51" 50' (x-ray). 110 A 110 = 68'58'. (x-ray). X-RAYDIFFRACTION DATA Cell Dimensions. a = 14.38 A.; b = 20.94 A.; c = 6.99 A. Formula Weights per Cell. 4 (3.983 calculated from x-ray data). Formula Weight. 404.5 (calculated for Cz2HsoOaN2. H,O); 402.8 (x-ray). Density. 1.271 grams per cc. (flotation); 1.276 grams per cc. (x-ray). OPTICALPROPERTIES Refractive Indices (5893 A,, 25' C.). 01 = 1.548 Z!Z 0.003, 6 = 1.620 rt 0.003, y = 1.670 ;t 0.003. Optic Axial Angle. 2V = (-)76" 24' (calculated from 01, p, and y). Optic Axial Plane. 001. Acute Bisectrix. cy = a. FUSION BEHAVIOR.Reserpic alcohol hydrate melts with decomposition a t 216-17" C.
Reserpic Alcohol Hydrate Powder Data d
6 00 5 82 3 42 5 01 4 89 4.65 4.56 4.43 4.02 3.97 3.76 3.64 3 32 2.27
1/11
hkl
d (Calcd.)
1 00 0 10 0 10 0 10 0 20 0.20 0.40 0.20 0.20 0.20 0.40 0.10 0.10 0.40
111 02 1 121 230, 201 03 1 131 22 1 320 23 1 330 321 250 022 251
6.02 5.81 5 40 5 01, 5 01 4 94 4.67 4.52 4.36 4.07 3.95 3.76 3 62 3.32 3.21
ACKNOWLEDGMENT
Reserpine Powder Data d 13 14 12 22 7 44 7 19 5 73
T h e author wishes to thank Sorbert Xeuss for the samples on d (Calcd ) 13 11 12 18 7 48 7 14 5 70
u hich these data were obtained and for information concerning
40
hkl 100 00 1 101 011 111
5.34 5.02 4.78 4.49 4.21
0.40 0.40 0.60 0.60 0.40
210 012 102 103 112
5.26 5.01 4.80 4.45 4.21
(1) Dorfman, L.,et al., Helv. Chim. Acta, 37, 59 (1954). (2) Neuss, N.,Boaz, H. E., and Forbes, J. W., J . A m . Chem. SOC., 75, 4870 (1953) (3) I b i d . , 76, 2463-7 (1964).
4.18 3.71 3.56 3.47
0.20 0.40 0.40 0.20
02 1 20'' 4oi 103
4 15 3.74 3.57 3.48
COSTRIBUTIONS of crystallographic d a t a for this section should be sent to Walter, C. McCrone, Analytical Section, Arrnour Research Foundation of Illinois Institute of Technology, Chicago 16, Ill.
1/11
0 0 0 1 0
40 40 20 00
the chemistry of the compounds. LITERATURE CITED
SCIENTIFIC C O M M U N I C A T I O N
Precipitation from Homogeneous Solution by Controlled Cation Release
P
R E C I P I T A 4 T I O Nfrom homogenous solution ( 3 , 4,8-10) is usuallybrought about by slow release of anions in a solution containing a metal ion. T h e literature on this subject was revien-ed by Willard ( 8 ) in 1950. Controlled release or generation of cations for purposes of precipitation from homogeneous solution has been reported only twice, by Heyn and Schupak (6) and by Willard and Yu (11). Heyn and Schupak released barium from bdrium Versenate complex in a sulfate solution by slow acidification of the solution. Willard and Yu precipitated the basic iodate of cerium, CeZ(IO3)iOH.rHzO, by slowly oxidizing cerium(II1) t o cerium(1V). T h e Heyn method is limited to those metals whose precipitates remain relatively insoluble in acid solution. T h e Willard method is limited t o oxidizable cations. I n addition t o the controlled release of anions and cations, Gordon and Shaver ( 5 )used the complexing power of ethylenediaminetetraacetic acid t o obtain selective separation of precipitates with proper temperature a n d p H adjustments. Beck ( 1 ) ha< also reported the separation of rare earths using acidification of nitrilo-triacetate complexes but did not specifically apply it t o preripitation from homogeneous solution. This communication reports the precipitation from homogeneous solution of hydrated ferric oxide b y a gradual release of ferric ion t o a solution whose p H remains nearly constant. Ferric ion is first complexed with Versene ( 2 ) in a solution of p H 3.0 t o 3.2. T h e Versene is then slowly destroyed with hydrogen peroxide over a period of about 1 hour. Comparisons of particle size, sedimentation volume, drying, and final ignition weights have been made between hydrated feriic oxide formed by the gradual release of ferric ions and hy-
h a t e d ferric oxide formed by the gradual increase of the hydroxyl ioii (9,10). Other oxidizing agents-namely, ammonium persulfate and sodium hypochlorite-were tried and found too vigorous. Sodium bromate is satisfactory, but its use is limited to acid solution.
Precipitation of Hydrated Ferric Oxide by Destruction of IronVersene Complex. T h e rate of oxidation of Versene by hydrogen peroxide was studied by mixing Versene with hydrogen permide a t various p H values. After suitable time intervals, the remaining Versene was titrated ( 7 ) with calcium chloride solution and Eriochrome Black T indicator. Experiments a t 70" t o 80" C. indicated complete oxidation of 50 ml. of 0.05M Versene reagent by 15 m]. of 3% hydrogen peroxide in about l hour. I n the presence of ferric iron, the oxidation of the Versene is slower. However, by increasing the concentration of hydrogen peroxide sufficiently, the oxidation could be brought about a t lower temperatures. T h e following conditions may be used for the controlled oxidation of the iron-Versene complex: Dissolve about 0.5 gram of ferrous ammonium sulfate hexahydrate in 25 ml. of 0.05M Versene solution and dilute to 100 ml. Add 20 grams of ammonium chloride, warm t o 30' C., and adjust the pII to 3.0 with 0.01X hydrochloric acid and 0.01N sodium hydroxide. Add 10 ml. of 30% hydrogen peroxide, and allow the solution to stand a t room temperature for 1 hour. Rising bubbles of oxygen provide sufficient stirring. The reaction is complete in about 1 hour. (Although the necessity for warming the solution in order to complete the reaction was not shown, the suspensions were warmed a t 90' t o 95" C. for 1 hour.) K a s h the precipitate several times with hot, 3% ammoniam nitrate until chloride free, filter on S. and S. No. 589 white iibbon paper or on a Gooch crucible with a fine asbestos mat.
For other amounts of iron, the quantities of hydrogen peroxide
1247
V O L U M E 2 6 , NO. 7, J U L Y 1 9 5 4 and ammonium chloride required are proportional. The total volume of solution need not be changed. In a series of 11 precipitations by this method, followed by washing, filtration, and ignition, the average deviation from the theoretical was 0.016%. I n similar series based on t h e urea method of Willard and Tang (9, I O ) , the average deviation from the theoretical was 0.017%. Precipitates formed by the T’ersene peroxide and urea methods were prepared and found t o have the same sedimentation volume, the same rate of settling, and the same behavior on low temperature drying and upon ignition. The agreement between ignition weights and t h e known weight of iron indicates t h a t impurities are not appreciable. These results demonstrate the probable general usefulness of the Versene-peroxide method for the controlled release of metal ions in precipitation from homogeneous solution. The strong complesing power of Versene ( d ) , for a large number of metal ions, makes possible the wide application of this principle t o t h e study of precipitation from homogeneous solution by the controlled release of cations. WILLIAM &I. & I A C x E Y I S MYRONL. DUSTON Department of Chemistry Ohio State University Columbus 10, Ohio LITERATURE CITED
(1) Beck, G., H e h . Chim. Acta, 29, 357 (1946). (2) Bersworth Chemical Co., Framingham, Mass., “The Versenes,” Tech. BUZZ.2 (1952). (3) Caley, E. R., and Simmons, G. A., ANAL.CHEM.,25,1386 (1953). (4) Elving, P. J., and Van Atta, R. E., Ibid., 22, 1375 (1950). (5) Gordon, L., and Shaver, K. J., Ibid., 25,784 (1953). (6) Heyn, A. H. A., and Schupak, E., Ibid., 26, 1243 (1954). (7) hlacxevin, W. M., and Sweet, T. R., “Quantitative Analysis,” pp. 212-15, Kew York, Harper and Bros.. 1952. (8) Willard, H. H., ANAL.CHEM.,22, 1372 (1950). (9) m’illard, H. H., and Tang, N. K., J. Am. Chem. SOC.,59, 1190 (1937). (10) Willard, H. H., and Tang, N. K., IND. ENG.CHEM.,ANAL.ED., 9, 357 (1937). (11) Willard, H. H., and Yu, S. T’Sai, ANAL.CHEM.,25, 1754 (1953).
RECEIVED for review December 9, 1953. -4ccepted March 17, 1954.
M E E T I N G REPORTS
Northwest Regional Meeting HE Northwest Regional Meeting sponsored by the Oregon. Washington-Idaho Border, Puget Sound, and Richland Sections of the AMERICAN CHEMICAL SOCIETY, was held at Richland, Wash., June 11 and 12. Abstracts of papers of special interest to analytical chemists are given here.
tendency for dibutyl phosphate to cause emulsion formation when present in a colloidal zirconyl phosphate solution in which carbon tetrachloride is dispersed is a basis for the determination. Dibutyl phosphate concentration was shown to be an empirical fuwtion of phase “disengaging time” when measured under standardized conditions. Modified Fluoride Method for the Determination of Aluminum. J. F. MURPHY AND R. V. PAULSON. h modified method for determination of aluminum, using the hydroxyl-releasing action of fluoride ion, in the pH range of 9 to 10, has been tested. A comparison with previously published met.hods was made. The new method avoids the difficulty of solid-solid reactions inherent in some other methods, and the necessity for additions to keep aluminum in solution. Results of analyses on both prepared aluminum solutions and solutions used in aluminum processing show satisfactory precision and accuracy. A Rapid Method for Precipitation Fractionation of Cellulose Nitrate. AND E. GRAYKING. CARLADOLPHSON ri rapid fractional precipitation method for the determination of the molecular weight distribution of cellulose was presented. The method was developed for routine precision analysis of dissolving grade celluloses with a view to obtaining results commensurate with the accepted conventional methods, but with the expenditure of a minimum of time and attention. Speed is attained by not washing the precipitates, while accuracy is maintained by correcting the size and molecular weight of each fraction for dissolved material in the solution removed with the precipitates. The importance of uniformity of treatment in the nitration step and its effect on the reproducibility of the determined D.P. distribution were stressed. Reproducibility tests show nearly identical distribution curves for the same nitrate. The method was compared with the summative method using nitrates of five different cellulose samples to show that the results are comparable.
The Determination of Diphenyl Mercury Alone or in the Presence of Phenyl Mercuric Compounds. V. L. MILLER AND DQROTHY POLLEY. In an investigation of phenyl mercuric fungicides, it became desirable to determine why some formulations appeared to give better results than others. One possible explanation was that diphenyl mercury, a relatively inactive material against the fungus under investigation, might be formed. The described procedures make possible the analysis of diphenyl mercury alone or in the presence of phenyl mercuric compounds. A procedure was given for the estimation of diethyl mercury alone or in the presence of ethyl mercuric compounds. Specific Microprocedure for Mercury in the Presence of Many Metallic Ions. DOROTHY POLLEY AND V. L. MILLER. A specific quantitative method for the determination of mercury is based on the reaction RzHg
+ HgXz +2RHgX
After adjusting the acidity, a n excess of an alcoholic solution of the RzHg compound is added to the solution to be tested and the resulting RHgX is extracted with chloroform. The amount of RHgX formed is measured colorimetrically using the diphenylthiocarbazone reaction. The compounds diphenyl mercury, di(nitropheny1) mercury, di(trifluorotolyl) mercury, and ditolyl mercury may all be used in the above procedure by varying the reaction conditions. The ditolyl mercury is the compound of choice, as it requires fewer manipulations.
Coulometric Determination of Phosphate. U‘. N. CARSON,JR., . ~ N DH. S. GILE. .4 microvolumetric method for phosphate determination has been developed which is based on the use of a cation exchange resin to convert the salts in the sample to a mixture of acids. The acids are titrated with electrolytically generated base; the amount of base required for the titration between a methyl red end point and a thymol blue end point is equivalent to the phosphate. A potentiometric end point can also be used. Precisions on micro samples are excellent.
X-Ray Photometry in Chemical Analysis. MAURICE C. LAMBERT. Application of x-ray photometry to the rapid determination of materials in solution is discussed and three variations of technique were described, including one with which it is possible to achieve a precision of 0.1%. Absorption of polychromatic x-rays was discussed as a function of atomic number, source voltage, and absorption leiyel. Absorption coefficients for a number of elements distributed throughout the periodic chart were portrayed as functions of source voltage and of atomic number, showing the anomalous behavior of the middle elements. A new model x-ray photometer was described alone with interchangeable cells of small volume.
Determination of Dibutyl Phosphate. D. W. BRITE AND R. H. MOORE. Dibutyl phosphate concentrations are determined in aqueous and organic solutions in the presence of tributyl phosphate, phosphoric acid, and equimolar concentrations of monobutyl phosphate. The
Isotopic Analyses of Solids Using a Modified Commercial 180’ Type Mass Spectrometer. G. J. ~ ~ L K I RAND E C. A. GOODALL The source and ion current amplifier of a 180’ gas type mass spectrometer have been modified to accomplish the isotopic analyses of
