tion of perchloric acid, reaction time. and reaction temperature. Only in the case of 3-chloropropene was the reaction quantitative. Typical data are shown in Table I. I n methanol, mercuric acetate reacts with ethylenir compounds as follows: Hg(CH,COO),
>p-$
+ CH,OH + >c=Cy-$
+ 2HC1+ HgCl?
+ 2CH3COOH
+ HCl+
OCHa HgO CO CHI
>.-$
+ CHBCOOH
OCH, HgCl Instead of thymol blue, \\hich IS more generally used (3, 4 ) , diphenylcarbazone was used as indicator in the titration with hydrochloric acid. It gives a strong blue-violet color in the presence of mercuric acetate or mercury addition products in methanol and immediately turns colorless when the
hydrochloric acid reacts conipletely to give undissociated mercuric chloride and acetir acid. Diphenylcarbazone was as effective as thymol blue and had an added advantage in that its use eliminated the need for the addition of sodium chlonde to a mercuric awtate solution containing free acid (3, 4). K h e n chloropropene solution is added to reaet with a known escess of niercuric acrtatt. in methanol, the amount of the compound c m be determined from the difference between thc two titers as follows: (a
- b)
x
1000
’\
=
moles of chloropropene
where acid titci i n milliliters for rragent solution b = acid titer for sample S = normality of acid a
=
ACKNOWLEDGMENT
The author expresses his grateful thanks to Philip W.West for laboratory facilities. LITERATURE CITED
( 1 ) Das, 31. S . , ANAL.CHEM. 26, 1086
(1954). (2) Johnson, J. B., Fletcher, J. K.. IDic1.. 31,1563 (1959). (3) Mallik, K. L., Das, M. N., ( ‘ h e m . CV Znd. ( L o n d o n ) 1959, 162. (4) Mallik, K. L., Dae, M. N., unpublishrcl work. ( 5 ) Marquardt, R. l’.. Luce, E; S . , AKAL.CHEM.20, 751 (19%). (6) Ibid., 21, 1194 (1949). ( 7 ) Martin, K.IT-.,I b z d , 21,921 (1949) KANAILAL11 II,I.Ih Coates Chemical Laboratories Louisiana State University Baton Rouge, La. Present address, Chemistry I k p a r t ment, University of Utah, Salt Lake City, Utah.
Determination of Ascaridol in Chenopodium Oil with Hydrogen Bromide in Acetic Acid SIR: The standard procedure (1) for determining ascaridol in chenopodium oil is based on the titration with sodium thiosulfate of the iodine liberated when the oil is treated with potassium iodide and hydrochloric acid. The conditions prescribed in the assay must be carefully controlled and, a t best, the procedure is an approximate one. Since the chemical reaction is not understood, the calculations involved are empirical. Other methods of analysis (5, 6) have been proposed but apparently offer no advantage. The procedure described here is a modification of a method proposed by Durbetaki ( 4 ) for the determination of osiraiie oxygen in eposy-type compounds
Analysis of Chenopodium Oil. . I sample of chenopodium oil, 150 t o 200 mg., is accurately weighed into a n iodine flask. Twenty milliliters of glacial acetic acid is added t o the flask, follotved by exactly 25 ml. of 0 , l Y hydrogen bromide solution. The flask is tightly stoppered, shaken briskly for 5 minutes, and permitted to stand a t room temperature for 21 hours, Excess hydrogen bromide is determined by titrating the solution potentiometrically n i t h a Fisher titrimeter equipped with a glass-calomel electrode system. A blank is run with a series of three analyses. A typical titration curve is shown in Figure 1. Results of analysis of chenopodium oil for ascaridol content are shon-n in Table I. Calculation. Per cent ascaridol is calculatcd from t h e expression :
Table I.
Analysis of Chenopodium Oil for Ascaridol Content
Recovery, h-ational formulary method
7c Proposed method
66.95 06 54 65 52 65.26 ti4.97 64.86 64 04
65.83 65.61 65.23 65.17 64.97 64.80 64.56
ti5 45
65.17
dev. 0.78
0.33
Av. AV.
EXPERIMENTAL
Reagents. Hydrogen biomide ill acetic acid, 0.1N ( 3 ) Sodium acetate, 0.1N (2).
1370
ANALYTICAL CHEMISTRY
Vol. 0.LV acetate ronsuined in blank - vol. 0.1W acetate consumed in run weight of sample, mg.
1
16.8
100 =
ascaridol
Reaction Time. Optimum reaction time was determined b y analyzing a series of Chenopodium oil samples which were treated with hydrogen bromide reagent for varying time periods u p t o a maximum of 60 hours. T h e d a t a in Table I1 indicate t h a t t h e reaction is complete after 20 hours. Twenty-four hours vias selected as a convenient time period foi this procedure.
Whereas the National Formulary method requires a sample weight of 2.5 grams, the proposed method requires 0.5 gram for a series of three determinations. Table I shows that comparable results are obtained. The only disadvantage of the proposed method is the 24-hour waiting period.
500
VI I-
O
?
400
-A
I
300
ACKNOWLEDGMENT /
2
Table II.
Ascaridol Content as Function of Reaction Time
Time. Hr.
Recovery,
%
2 5 10
47.46 57.06 61.17
15 20 30 45 60
63.25
65,10 64,83 64.95
65,39
Standard Procedure. For comparntive purposes, oil sanil)lcs were analyzed according t o thc iodometric method of the Xational Formulary ( 1 ) . Results arc reportid in Tahle I. DISCUSSION
The proposed method for the determination of ascaridol in chenopo-
193.
,
I 4
ML. 0.1
/
1
,
1
6
N
SODIUM
8
I
1
1
1
1 0 1 2
ACETATE
Figure 1 . Titration of excess hydrogen bromide with 0.1 N sodium acetate solution
The authors thank Fritzsche Brothers, Inc., New York 11, N. Y., for financial support in this project. LITERATURE CITED
( 1) American Pharmaceutical Association,
dium oil is a simple and accurate one. Since the reaction is slow, residual titration is employed. The reaction mixture develops a dark brown color, making visual titration impossible. Excess hydrogen bromide is therefore determined by potcntiomrtric titration. The titration i n ~ o l ~ ea bstrong acid-b:isc system and :I \harp break is obserwd in the titration c u r w (Figuw 1). -1blank is run with racli wries of three determinations to c0rrec.t for cha1igi.s in normality of the hydrogen bromide reagent. Thr. hyrlrogcn bromide solution should l ~ cstorcd in a tightly stoppered container and should be colorleas or very faiiitlv pale yrllmv.
Was!,ington, D. C., “Sational Formulary, 10th ed., p. 148, 1955. (2) Blake, h4. I., J. Am. P h a m . Assoc., Sci. Ed. 46, 163 (1957);( (3) Duncan, D. R., Inorganic Syntheses,” Vol. 1, p. 151, PvIcGraw-Hill, New York. 1939. (4) Durbetaki, A. J.. XYAL. CHEJI. 28, 2000 (1956). ( 5 ) Nelson, E. K., J . A m . P h a m Assoc., Scz. Ed. 10,836 (1921). ( 6 ) I’ag~t,H , Analyst 51, 170 (1926). hfARTIN I. B L A K E Chemistrj- Division Argonne National Laboratory Lemont, Ill. RICHARD E. O J N ~ : ~ ~ ~ , School of Pharmacy North Dakota Agricultural College Fargo, N. D.
Tetrahydroalstonine
HARRY A. ROSE, Eli Lilly and Co., Indianapolis 6, Ind.
been discussed by Elderfield and Gray (1).
Structural Formula ETRAHYDROALSTONIXE is derived T f r o m the alkaloid alstonine b y reduction with hydrogen over platinum. The chemistry of these compounds has
Thc x-ray powder diffraction data were obtained using a camera 114.6 nim. in diameter and chromium radiation with vanadium filter. A wave length value of 2.2896 A. was used in the calculations. The indrxing was done on the basis of a single crystal rotation pattern around the c axis.
CRYSTAL MORPHOLOGY Crystal System. Orthorhombic. Form and Habit. Blades elongated parallel to c and lying on 010.
Axial Ratio. a : b : c = 0.2399:l: 0.1997. Cleavage. Good, parallel to 001. x - R . 4 ~DIFFRACTION DATA = 8.18 A , , Cell Dimensions. 60 = 33.10 A., CO = 6.81 A. Formula Weights per Cell. 4. Formula Weight. 352.4. Density. 1.245 grams per CC: (flotation), 1.244 grams per cc. (x-ray). OPTICALPROPERTIES Refractive Indices (5893 A,, 25’ C,). a = 1.586, p = 1.608, y = 1.64 (est.). Optic Axial Angle. 2V = 80’ (est.). Optic Axial Plane. 001. Acute Bisectrix. y. Optic Sign. Positive. Orientation. y = b. VOL. 32, NO. 10, SEPTEMBER 1960
1371
