.."...",._
16. Allylthiourea (Thiosinamine)
tained during recrystall .lll.l.. y u room tempers, ture. Figure 1 shows the solution phase transformation at room temperature. The large veil-formed rods of I are growing rtt the expense of the fine grained crystals of I1 in thymol.
E"""
'LLENT crystals of allylthiourea are obtained from water either an a microscope slide (Figure 1) or on a larger scale. AII the crystals used in this work were obtained in this way; large crystals for x-ray diffraction were orystdlized slowly by evaporation of 8.n aqueous solution. Allylthiourea exists in a t least two polymorphic forms The stable form is most readily (and perhaps always) obtained by recrystallization from water. The unstable form is always oh-
ALLYLTHIOUREA (1) ,., . , .DY .w_. .G.- .1VlCGraneJ. _ r jaezerminea
PHOLOGY
Crystal System. Monoclinic. Form and Habit. Tablets and rads elonoat,ed nmalld t,o "~~~~ .. h- I showinec the basal and orthoDinacoids IO01 I and. 11001: , , prisms { 1101;~clinodome l o l l ) ; a d several 6the;orthodome farmsineluding (2011,(5021, [301},and [401/. Axial Ratio. a:b:e ' '".'.nn"c Interfacid Angles 79 -. t a Angle. 120"36'. LY,DIFFRACTION DAT.I (det,ermined by J. F. Whitney and rvln). 11 Dimensions. a = 9.76 A.; b = 8.57 i.; e = 8.37 1. rmula Weights per Cell. 4. rmula Weight. 116.18. ~
~~~~~~~~
~~~
~
Figure 1. Allylthiourea Right.
Left. Crystals from water on microscopa slide Solution phase polymorphic trandmmntion in thgmol on miorosoopr slide
,b 2.1
2.. 2.'
2:
OPTICALPROPERTIES (determined by W. C. McCrone and A. Smednl). Refractive Indexes (5803 A,; 25' C.j. a = 1.602 * 0.002. B = 1.684 * 0.002. = 1.74 + n . w Optic Axial Angles (5893 A,; 2 5 O C . ) , 271 = 77". 2H = 88". Dispersion. II > I Optic Axial Plane. 010. Sign of Double Ref ractiou. Negative. Acute Bisectrix. y A (. = 15" in acute 8. Extinction. a A a = 45' in obtuse 8. Molecular Refractic)n (Rj (5803 A,; 25'C.). = 1.67 R (calcd.) = 35.1. R (obsd.) = 34.8. FUSION DATA(deterniinod by W. C. McCrone). Allylthiourea melts a t 77-78' C. with neither decomposition nor sublimation. Crystallization is spontaneous and may give either fine grained crystals. of the unstable form which grow rapidly or coarse grained rods of the stable form which grow slowly. The transfarmation occurs only very slowly even in the presence of thymol melt or water as a solution medium. Allylthiourea (I) grows elongated parallel to 2, and shows all possible interference figures [ZV = 77"; v > r; (-11 and orientations. Allylthiourea (11) is very slowly changed to I at room temperature. A melthack of I1 gives larger rads which show 2E = 128'; v > I ; (+). CORRECTION.I n the article on "Rapid Wet Combustion Method for Carbon Determination" by Lindenbaum, Schubert, and Armstrong [ANAL. CHEM., 2 0 , 1120 (1048)1, the reagent used in the authors' experiments was incorrectly named. The term chromium trioxide and the formula CrOs should have been used instead of chromic oxide and CnOl.
Figure 2. Orthographic Projection of Typical Crystal of Allylthiourea
421
