Contributed hy WALTICK C. McCIIONE, DONALD GKABAK, AWLI EUGENE LIEBER Armour Research Foundation oC lllinoin Institute of Technology, Chicago 16, Ill.
42.
angles were measured microseopieslly and are subject to *3' error. This accounts also for the rather bad agreement between the observed and oalculated density.
Tetrazole H
N-N,
I/
CH
N-d
Figure 3. Orthograpliio Projection of Typical Tetrazo1e;Crystal
= 411.
Structural Formula for Tetrazole TETKAZOLE can he recrystallizcd from ethyl acetate and other common organic solvents, hut the best crystals far hoth optical and x-ray studies are obtained by slaw sublimation (at ahout 50"C.) onto it mieroscopc slide. Characteristic crystals by sublimation are shown in Figure 1; crystals grown from the melt arc shown in Figure 2. An orthographic projection of a typical crystal of tctrssole is shown in Figpure 3. 411 crystal intcriacial
CRYSTAL MoRrHoimx Cryfits1 System. Triclinic. Form and Habit. Plates flattened parallel to and usually lying on 001, showing the pinacaids, (001 I, ( O l O ) , { l O O i , and oceasionally theprisms, { 110). AxialRatio. a : b : e = 0.915:1:0.687. Interfacial Angles (Polar). 001 A 100 = 86'; 001 A 010 = 57.5"; 10OAO10 = 106". Crystal Angles. a = 130"; B = 111"; y = 63". X-RAYDIFFRACT~ON DATA Cell Dimensions. a = 5.00; h = 5.16; c = 3.75. P o m u l a Weights per Cell. 1. Formula Weight. 70.06. Den&. 1.406 (flotation); 1.632 (x-ray). Principal Lines d
Figure 1.
d
Crystals of Tetraaole Sublimed onto Microscope Slide
OPTICAL PROPERTIES 6
Refractive Indexee (5893 A,; 25" C,), a = 1.388 * 0.005. = 1.595 + 0.002. y = 1.660 * 0.002. Optic Axial Angles (5893 A ; 25" C.). 2V = 51". 2E =
"" . il"
0
Dispersion. v> rveryslight. Sign of Double Refraction. Negative. Aciitr Biseotrir. Almost -001. Extinct&. yAa = 13"onOOl. xy = 1.54. Molecular Refract.ion (R)(5893 A.: 25" C.). q R(calcd.) = 19.7 (imidinevdue for N's). R(ohsd.1 = 15.6. FUSION DATA.Tetrasole melts without decomuosition at 155.5' ~~~
Figure 2.
C o ~ ~ n i e u ~ r o rofr crystallographic a data for this section should be sent t o Welter C . MoCrone, Analytical Section, Armour Research Foundation of Illinois Institute of Technology. Chiorm 18, 111.
Crystals of Tetrarole from Melt Crossed Niools
543
