CRYSTALLOGRAPHIC DATA. 48 Tetrachlorophthalic Anhydride

---

V O L U M E 23, N O , 9, S E P T E M B E R 1 9 5 1 acids (4). The diversity of the compounds anslysed in this work with no rccovcries below 96% of theory demonstrates that thc regular Kjeldahl microprocedure, with the nddition oi tho sealed-tube hydrolysis for acrylonitrile, is entirely satisfactory for many nitrilcs and suggests t h a t it is probably generally applicable.

139 LITERATURE CITED

X. P., "Semimicro Quantitative

Organic Analysis," p. 37, New York, Academic Press, 1943. F..Ind. Eng. Chon., 37, 482

(1) Clark,

(2) Davis, H. S., stid Wiedeman, 0. 1194.51.

ACKNOWLEDGMENT

The authors express their thanks to L. L. McKinney and F. H. Stodola for the generous samples of most of the compounds used

211 (1945). (7) Willits, C. O., Coe, M. R..and Ogg, C. L.. .I. Assoc. O&. Chaists.32.118 (1949). . . .

in this study.

REOE~E Deoember4.1950 D

Aqr.

48. Tetrachlorophthalic Anhydride Contributed by W. C. MCCRONE, Armour Researoh Foundation of Illinois Institute of Technology, Chicago 16, Ill.

0

CI

I

//

C

C

CI-C -

L\\ c

/I

\ 0

,,c;\C/

I

CI hydride may hydrolyze to the acid water; hence this solvent should not he used. Ether and benzene are satkfactory, although by ie the bcst crystals for analytical purposes are obtained by slow sublimation in a Kofleer block a t about 150" C. (Figure 1, A ) . Below 150' C. long rods and needles are formed; above 150" C. more massive crystals can he iormed. l h e latter method of preparing crystals is particularly good in this case bccaurc m y beid present is converted by sublimation t o the anhydride. A very unstable polymorphic farm is sometimes obtained from the melt (me hclow). ~

LcbLJoyL2LiyL"LLyy

llylll

CRYSTAL MORPHoi.oGY Crystal System. Monoclinic. ' Form and Habit. From sublimation stubby and long rods elongated parallel to hL The orthopinacaid I I O O ] and the positive hemiort,hodome [ 101 1 closcd by eit.hcr the clinopinscaid or

Figure 2. Orthographic Projection of Typical Crystal or Tetrachlorophthalio Anhydride the positive hemipyramid (1111. The hemiorthodome (2011 and the basal pinamid 1001 are also common. AxialPatin. a : b : c = 3.104:1:2.11_6. Interfacial Angles (Pol:~r). 100 A 101 = 91"; 001 A 201 =

lmDRn' -..

Bets. Anglc.

132". Princioal Lines

d

6.10 4.5h

4.17 3.57 3.40 3.32 3.11 2.99 2.89 2.80 2.75 2.60 2.59 2.43 2.36 2.27 2.22

.

I/If 0.07 0.13 0.26 0.86 0.12 0.21 0.01 1.00 0.14 0.87 0.93 0.05 0.53 0.10 0.27 0.16 0.32

d 2.12 2.11

2.07 1.93 1.89 1.86 1.79 . 1 .76

1.73

1.68 1.64 1.57 1.46 1.44 I.3R 1.36

I/II 0.31 0.34 0.47 0.43 0.12 0.5 0.2 0.3 0.2 0.1 0.6 0.1 " 7

X-RAYDIFFRACIIOV DATA Cell Dimensions. a = 18.10A.; b = 5.83 A.; c = 12.34A. Formula Krights per Cell. 4 (3.994 x-ray).

ANALYTICAL CHEMISTRY

1340 Formula \\-eight. 285.43. Density. 1.970 (flotation plus pycnometer).

1.973 (x-ray).

OPTICAL PROPERTIES Refractive Indexes (5893 .4,; 250 c,). a = 1,612 & 0.002, @ = 1.737 zk 0.004. y = 1.88 & 0.01. 25' C.). 2V = 87". Optic -4xial Angles. (5893 Dispersion. z' > T . Optic Axial Plane. 010. Sign of Double Refraction. Positive. Acute Bisectrix. 0 1 . Extinction. y I. n = 14" in obtuse p. Molecular Refraction ( R ) (5893 A . ; 25' c.). = 1.740. R(ca1cd.) = 58.4. R(ohsd.) = 54.5.

+&

FCSION D a ~ a . Tet,rachlorophthalic anhydride melts a t 255257" C. with considerable sublimation. Well-formed rods (Figure 1, B ) showing parallel extinction and off-center optic axis figures [2V = 8 7 " ; ( - ) ; (v > T ) ] are common in the subhmate. When completely melted, a n extremely unstable polymorph grows for an instant before a solid-solid transformation occurs; the remaining melt solidifies very quickly. These crystals and those obtained on meltback show the off-center optic axis figure. Characteristic shrinkage cracks are clearly visible (Figure 1, B ) . COSTRIBCTIOSS of crystallographic d a t a for this section should be sent t o Walter C. Alecrone, supervisor, Analytical Section, Armour Research Foundation of the Illinois Institute of Technology, Chicago. Ill.

....

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