1067
V O L U M E 2 2 , N O . 8, A U G U S T 1 9 5 0 sive 10-ml. portions of water. If the residue dissolves com letely in the 2 ml. of 6 N hydrochloric acid, omit the filtrdion angdilute the solution to 40 ml. in the separatory funnel. Let the solution flow through the column of resin a t a rate of 20 ml. per minute, and collect the eluate in a 250-ml. Erlenme er flask. Wash the se aratory funnel and column with one 20-mf portion and one 40mll portion of water. Add 50 ml. of concentrated hydrochloric acid to the eluate to bring the concentration of this acid up to 4 M . Add 1 gram of sodium bicarbonate, 0.2 gram a t a time, swirling all the while. Add 1 gram of potassium iodide, stopper the flask, and swirl until all the iodide is dissolved. After 5 minutes, titrate, without starch indicator, with 0.05 N sodium thiosulfate to the disappearance of the iodine. Recognition of the end point may be facilitated by performing the titration on a porcelain stand. In the presence of starch, the reaction between iodine and thiosulfate is retarded, so that an appreciable quantity of thiosulfate reacts with the acid. The size of the sample should be decreased to about 0.1 gram with insecticides containing over 3070 of arsenic because the end point becomes indistinct if more than 30 ml. of thiosulfate are used in the titration. Procedure for Quinquevalent Arsenic. Weigh 200 mg. of sample into a 150-ml. beaker and add 10 ml. of 2.4 N hydrochloric acid. Place in a water bath between 60" and 80" for 15 minutes. Filter the sample and proceed as previously described. Procedure for Trivalent Arsenic. Weigh 200 mg. of sample into a 150-ml. beaker and add 10 ml. of 2.4 N hydrochloric acid. Place in a water bath between 60" and 80" for 15 minutes. Filter the sample and wash through the column as previously described
Neutralize the acid present in the eluate with 10 N sodium hydroxide and adjust to the acid side of phenolphthalein with dilute hydrochloric acid. Add 4 or 5 grams of sodium bicarbonate. Titrate the solution with 0.05 N iodine using starch as an indicator. RESULTS
The results of the analyses together with the mean deviations, presented in Table I, indicate that the accuracy and precision of the recommended methods are satisfactory. Each entry in the table is the mean of at least three determinations. ACKNOWLEDGMENT
The authors Itre grateful to the Research Council of Rutgers University for financial aid in the investigation and to Kenneth Helrich of the Agricultural Experiment Station of Rutgers University for samples used in the analyses. LITERATURE CITED
(1) Aasoc. Offic. Agr. Chemists, "Official and Tentative Methods of
Analysis," 6th ed., p. 53, 1945.
(2) Kunin, Robert, ANAL.CHEM..22, 64 (1950). (3) Nachod, F., "Ion Exchange," S e w York, Academic Press, 1949. RECEIVED October 28, 19-19. Presented before the Division of Analytical and Micro Chemistry at the 116th Meeting of the A\IEWCAXCHEWCAL SOCIETY, Atlantic City, N. .J.
33, 34, 35. Symmetrical Diphenylurea, Unsymmetrical Diphenylurea, and Potassium Chlorate
4
Contributed by WALTER C. MCCRONE, Arrnour Research Foundation of Illinois Institute of Technology, Chicago, Ill.
N RECENT months, inquiries have been received requesting Ierythritol, crystallographic data on the following compounds: penðer dipentaerythritol, pentaerythritol tetraformate, onitrophenol, diphenyl, apocupreine hydrobromide, and vanadium fluorides. Any information on the crystallography of these compounds, no matter how fragmentary, should be sent to the National Registry of Crystallographic Data, in care of the author, who will transmit the information to interested parties. During the course of this program, a number of incomplete descriptions have accumulated. Although in some cases these compounds merit completion, most of them are less common or less important and would not be completed. The data are, however, accurate so far as they go and furnish adequate information for analytical purposes. Three of these partial descriptions are, therefore, being published this month. The orientations of the crystallographic axes are based on morphology and might change if x-ray diffraction data were available. Each has, however, been reoriented to agree with the conventions used in this series. 93.
SYMMETRICAL DIPHENYLUREA (CARBANILIDE)
:
C&-
\
7" 4
Car-N
Struetural Formula for Symmetrical Diphenylurea
C
-a
l
a
oii
I
A
Figure 1. Orthographic Projec-
tion of Typical Crystal of Sym-
metrical Diphenylurea
CRYSTAL MORPHOLOGY (see Figure 1) Crystal S stem. Orthorhombic. Form anc?Habit. Tablets from hot ethyl alcohol are flattened parallel to b with rism l l O ) , and macrodome { 1011, showing also ioloy, (oolj, and brachydome [ 011 ). Axial Ratio. a : b : c = 0.8957:1:0,5712; 0.8611:1:1.1165 (a). Interfacial Angles (Polar). 110 A 110 = 96'; 011 A o l i = 105'.
lvl,
ANALYTICAL CHEMISTRY
1068
OPTICAL PROPERTIES
RefractiveIndexea(5893A.; 25'C.l P = 1.58l;Zp = 1.624; y = 1.818(calcd.). Optic Axial Angle (5893 A.; 25' C.). 2 8 = 50'; 2E = 56'30' (3). Dispersion. Strong, r > u. Optic Axial Plane. 001. Sim of Double Refraction. Positive. Ofkical Orientation. Bx. = a. Densit 1.239(3). Formura Weight. 212.24. Molecular Refraction. q z y = 1.6il. R (calcd.) = 64.8. R (obsd.) = 64.4.
.
34.
UNSYMMETRICAL DIPHENYLUREA
cas
malt solidifies spontaneously to give the m e crystal form and orientation 88 is obtained on sublimation. The crystal-front is angular with all anglea 90". The crystals &ow parallel extine tion with a slow component parallel to the dvection of growth. All the crystals show a BZOinterference figure. When the p r e p aration is overheated, a aolid decom osition product is formed which crystallizes from the melt as Eigh blrefringent rods and needles having a positive sign of elongation. M. POTASSIUM CHLORATE, K C l G
Excellent crystals of potassium chlorate are obtained from aqueous solutions on a microscope slide.
C
B-
0
X--%--"* /
CEHS
Structural Formula for Unsymmetrical Diphenylurea
a'
Unsymmetrical diphenylurea yields good crystals from sublimation and from alcohol solutions. C
h 70°30'
Figure 3. Orthographic Projection of Typical Crystal of Potaseium Chlorate
'a
101-
Figure 2. Ortho aphic Projection of Typical g y e t a l of Unsymmetrical Diphenylurea
a CRYSTAL MOFPBOLOGY (see Figure 2) Crystal System. Orthorhombic. Form and Habit. Tablet6 from hot ethyl alcohol, showing the Drkm 11101, brachydome l o l l \ , { O l O \ , and (0131. The 011 faces are oft& re h i e d by a'001 face a t the ends of the crystal. Generally the &ea1 habit is altered by the development of a 010 face upon which the crystals lie. Axial Ratio. a : b : c 0.8183: 1:0.8093; 0.9891:l: 1.2221
-
(9).
Interfacial Angles (Polar). 110 A i i o = 79'; 011 A o i l = 78'. Density. 1.276 (9). OPTICAL PROPERTIES Refractive Indexes (5893 A.; 25' C.). P = 1.645; B = 1.651; y = 1.703. Optic Axial Angle (5893 A.; 25' C,), 2V = 38'; 2E 43'32'
CRYSTAL MORPHOLOGY (see Figure 3) Crystal System. Monoclinic. Form and Habit. P l a t e with clinodome, (011); and pin% coid, Il00) A & l R h o . a : b : c = 1.268:1:0.83&2(4). Interfacial Angles (Polar). 011 A 011 = 76"lO' Beta Angle. 109'38' (4). Twinning Plane. Parallel to 100. X-RAYDIFFRACTIONl d ) S ace Group,--Cif (&/M). &ll Dimensions. a = 7.086 A.; b = 5.585 A,; c = 4.647 A. Formula -We@ts per - --C_e!l. 2. W---..l. nuruura Weight. lY'2.55. Densit 2.32 ( 1 ) ; 2.33 (x-ray). OPTICAL i & o P E R m B
-
Refractive Indexes (6893 A.; 25' C.). a = 1.415 * 0.005 1.473 (calcd.). 6 = 1.517 * 0.002; y = 1.523 * 0.002; 19' (shown by plates lying on 001). Refractive Index (Average). i/= 1.484 (obad.); 1.478 (calcd. from Gladstone's formula). Optic A+al Angles (5893 A.; 26' C.). 2V = 28"; 2 E = 43'. Dispersion. Weak horizontal, u > r. Optic Axial Plane. 1010. Sign of Double Refraction. Negative. Extinction. a A. ,3 39' in acute 6. Optical Orientation. y = b ; P Bz. and 58.5' from a in the obtuse angle 8.
-
9
-
9
/a\
(W).
Dispersion. Strong, u > r. Optic Axial Plane. 001. Sign of Double Wraction. Positive, Optical Orientation. Bz. = a. Densit 1.276(8). Formura Weight. 212.24. Molecular Refrraction. = 1.666. R(obsd.) = 63.3 R calcd.) = 64.0. DATA. Unsymmetrical diphenylurea sublimes on heating to ive firsborder gray plates and tablets, which are usually shadec? more heavily on two ends. The crystals show 90' profile angles and a Bzo mterference fi re.' On further heating, melting occurs (186' C.) with very %le decomposition. The
.
A US ION
It is a pleasure to acknowledge the assistance of John Krc, Jr., in preparing this material for publication. LITERATURE CITED
(1) Fischer, P., N w e a Jahrb. Min. Ueol. (Beil. Bd.), 32,31 (1911). (2) Groth, P., "Chemische Kristallographie," Vol. V, p. 61, Leiprig, W. Engelmann, 1919. (3) Ibid.,p, 177. (4) Zachariaren,W. H., 2.Krakt., 71,601 (1929). CONTRIBUTIONI of oryntallogrsphio data for thia motion ahould he sent to Walter C. MoCrone, Analyticd Section, Armour Reaearch Foundation of Illinoir Institute of Technoloip', Chicago 16, Ill.
