V O L U M E 2 7 , NO. 1 2 , D E C E M B E R 1 9 5 5 Normal lead styphnate is very insoluble in most of the usual solvents; hence is usually studied as first precipitated. Many solvents in which this compound dissolves hot,-e.g., ethylene glycol-form crystalline solvates on cooling. CRYSTAL MORPHOLGQY Crystal System. Rlonoclinic. Form and Habit. As precipitated from styphnic acid and lead nitrate by sodium hydroxide rods elongated parallel to a are usually formed. Slight flattening, so that many crystals lie on the 001 face, is usually observed. Other forms shown are: prism (llO), clinodome (Oll), and the orthodome (101). Axial Ratio. u:b:c = 0.800: 1:0.640, 0.799: ::0.638 ( 2 ) ~Interfacial Angles (Polar). 110 A 110 = 102 . 011 h 011 = 65.4”; 68’ ( 2 ) . Beta Angle. 91.9’; 93 ( 2 ) . X-RAYDIFFRACTION DATA Cell Dimensions. a = 10.06 A.; b = 12.58 A , ; c = 8.05 A. u = 10.02A .; b = 12.54 A.; c = 8.00 A. (2). Formula Weights per Cell. 4 (4.05 calculated from x-ray dn t.R \.---, Formula Weight. 468.31Density. 3.095 (flotation in CHJ2-CClr); 3.055 (x-ray).
Figure 2.
Orthographic projection of typical crystal of normal lead styphnate
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CORRESPONDENCE Colorimetric Determination of N-Trichloromethylt hiotetrahydrophthalimide SIR: I t has been brought to my attention by Arnold S. Roseman, University of Massachusetts, that the captions of Figures 1 and 2 of my article on “Colorimetric Determination of N-Trichloromethylthiotetrahydrophthalimide” [ANAL. CHEM., 24, 1173-5 (1952)l are confusing. The original work on this procedure !vas carried out using a manually operated spectrophotometer. Kith this instrument the absorbance peak a t 425 mp was missed and all the data in Table I and Figure 2 were obtained a t 450 mp. When a recording spectrophotometer was used, the curve shown in Figure 1 was obtained. This curve showed that a higher degree of accuracy would be realized by using 425 mp instead of 480 m p and therefore the lower wave length was suggested in the procedure. If an analyst were to apply this analytical procedure, hewould make his own standard curve, in which case it would be best to use the 425 mp wave length. Possibly a more significant correction could be made regarding this article, which states: “The structure of the chromogenic reaction product has not been precisely determined, but is undoubtedly of the phthalein type that could be expected from the reaction of resorcinol with the dibasic acid portion of the SR-406 molecule.” I t has since been found that the color produced is the result of reaction between resorcinol and the -SCCI, group. This is substantiated by the fact that perchloromethyl mercaptan (CISCCla) gives the same color reaction nith resorcinol. &o, other compounds containing the -SCC1, group, such as S-phenyl AT-trichloromethylthiomethylsulfonamide, give the same transmittance curve as SR-406 between 300 and 500 mp when heated with resorcinol under the described conditions. ALLENR. KITTLESON Em0 Research sild Engineering Co. Linden. S.6.
OPTICAL PRGPERTIES Refractive Indices (5893 A ; 25‘ C.). CY = 1.554 i 0.002. /3 = 2.20 f 0.03. y = 2.22 & 0.03. CY’ (in 001) = 1.833 Z k 0.01. Optic Axial Angles (5893 A , ; 25‘ C). 2E = 57‘. 2V = 25“. Dispersion. t > b, very strong. Optic Axial Plane. 010. Sign of Double Refraction._oNegative. Acute Bisectrix. d a = 4 t in obtuse 8. Molecular Refraction ( R )(5893 A , ; 28’ C.), y/(ypy= 1.965; R(obsd.) = 73.9. R(ca1cd.) cannot be calculated, since the molar refraction for lead is not known; the partial value not including the lead is 43.2, indicating that the molar refraction of lead is about 30. ACKXOWLEDGMENT
Some work on normal lead styphnate by McCrone a t Cornell in 1944 was reported under Contract OEJlsr-193 between Cornell University and the Office of Scientific Research and Development. This work has now been reviewed and completed under Contract DAI-11-022-ORD-P-18 between The Armour Research Foundation and Army Ordnance. REFERENCES
(1) Blomquist, A. T., Office of Scientific Research and Development, “Microscopical Examination of Primer Compositions,” OSRD 3757 (July 1, 1944). (2) Miles, F. D., J . Chem. Soc., 1931, 2532.
CONTRIBUTIONS of crystallographic data for this section should be sent t o Walter C. McCrone, Analytical Section, Armour Research Foundation of Illinois Institute of Technology, Chicago 16, Ill.
CORRECTIONS Far Ultraviolet Absorption Spectra of Unsaturated and Aromatic Hydrocarbons In the article on ‘‘Far Ultraviolet Absorption Spectra of Unsaturated and Aromatic Hydrocarbons” [Jones, L. C., Jr., and Taylor, L. W., ANAL.CHEM.,27, 228 (1958)) in Figure 13 curve A should have been identified as n-decylcyclohesane.
Redox Determination of Tervalent and Total Cobalt in Presence of Excess Tungstate In the article on “Redox Determination of Tervalent and Total Cobalt in Presence of Excess Tungstate” [Baker, L. C. W., and McCutcheon, T. P., ANAL. CHEM.,27, 1625 (1985)l in the last sentence in the first column the words “It was evident that such lower states exist in the cobalt determination” were printed twice in error. In the first paragraph on page 1626 (2, 6) in the 17th line refers to Literature Cited, as do ( I , 3, 15) in the 20th line, and (I, 2, 6, 1.5) in the 22nd line. In reference (6) the volume number is 39.
