ANALYTICAL CHEMISTRY
2008 I n order t o keep the relative analysis error within 1.0%, the hydrazine concentration must be \Tithin the limits 0.06 t o 0.47 p.p.m. ; these limits were determined exactly as described by ilyres and Young (S), assuming 0.2% absolute photometric error. The susceptibility of hydrazine t o catalytic oxidation and/or decomposition (1, 4 ) was confirmed; results shovi that hydrazine solutions should be analyzed as soon as possible after preparation. In the present method, errors become appreciable after 12 hours. For this reason, freshly prepared standard hydrazine solutions iyere used in all measurements involved in the calibration data. With reference t o interferences, it is clearly evident that the progressive change in the spectral curve for semicarbazide results from the slow hydrolysis of this component to produce hydrazine. Although the rate of hydrolysis is slow, the color reagent is more sensitive t o hydrazine than to semicarbazide, and this causes a shift in the minimum transmittancy to that characteristic of hydrazine. In the study of interferences, therefore, freshly prepared solutions of semicarbazide were employed. -4s shown by the data of Table I, at a hydrazine concentration of 0.26 p.p.m. (29.7% tmnsmittancy a t 25" C.), a molar concentration of semicarbazide 25 times as great as that of hydrazine introduces a relative error of only 1,3%, but the magnitude of the error increases with decrease in hydrazine concentration. A relative error of 1.6% results when the molar concentration of urea is 55 times as great as that of hydrazine. If both urea and semicarbazide are present, the relative error is increased over
that attributable to either component in the absence of the other, but the increase is not great. Thus, if the hydrazine concentration is 0.26 p.p.m,, the per cent relative error is 1.6 if the solution contains 25 moles of urea and 25 moles of semicarbazide per mole of hydrazine. ACKNOWLEDGMENT
The work described in this paper !vas supported by the U. S. S a v y Bureau of Ordnance under Contract K123s-67363, Task Order 2. LITERATURE CITED
Audrieth, L. F., and Mohr, P. H., I n d . Eng. Chem., 43, 1774 11951 ). h y r e s , G. H., A s i L . CHEY, 21, 652 (1949). Ayres, G. H., and Young, Fiedeiick, Ibid., 22, 1280 (1950). Bray, W, C.. and Cuy, E. J , J . Am. Chem. Soc., 4 6 , 8 5 8 (1924). Gilbert, E. C., J . Am. Chem. Soc., 46,2648 (1924). Jamieson, G. S.,Am. J . Sci., 3 3 , 3 5 2 (1912). Kolthoff, I. AI,,J . Am. Ckem. Soc.,-46,2009 (1924). Kurtenacker, A , , and Knbina, H., 2. anal. Cliem., 64, 388 (1924). Penneman, R. A , , and .ludrieth, L. F., ANAL.CHEM.,20, 1058 (1948). Pesez, M , , and Petit, .i..BUZZ.S O C . chim. France, 1947, 122-3. Smith, G. F., and Wilcox, C. S., IXD. EXG.CHEM.,ASAL. ED., 1 4 , 4 9 (1942). RECEIVED for review J u n e 10, 1952. -4ccepted September 25, 1952.
63. 4,6-Dinitroresorcinol Contributed by WALTER C. MCCRONE AND IRENE CORVIN, .4rmour Research Foundation of Illinois Institute of Technology, Chicago 16, Ill.
OH I
o~H-A U-OH
X-RAYDIFFRACTIOS DATACell Dimensions. a = 11.07 A . ; b = 5.03 A , ; c = 11.79 A . Formula Keights per Cell. 4 (4.01 calculated from x-ray data). Formula Keight. 200.11. Density. 1.786 (flotation in aqueous zinc chloride); 1.781 (x-ray).
I
ii-O* Principal Lines
Structural Formula for 4,6-Dinitroresorcino1 E X C E L L E N T crystals of 4,6-dinitroresorcino1 can be obtained either by sublimation or by recrystallization from ethyl alcohol. Both techniques give massive crystals and tablets shoxing the forms: prism, f IlO], orthopinacoid ( loo), and basal pinacoid (001J. Good crystals can also be obtained from thymol on a microscope slide. CRYSTAL MORPHOLOGY Crystal System. Monoclinic. Axial Ratio. a : b : c = 3.394:1:2.344. Interfacial Angles (Polar). 110 h IT0 = 136" 40'. Beta Angle. 48". OPTICAL PROPERTIES Refractive Indices (5893 A , ; 25" C.). CY = 1.598 f 0.002. 0 = 1.6T3 i 0.002. -/ = 2.01 (calculated from a,P , and 2V). Optic Axial Angles (5893 A.; 25' C.). 2V = 50" ( + ) (measured). 2 E = 91" Dispersion. r > v . Optic Axial Plane. 010. Acute Bisectrix. y. Extinction. y A a = 3" in acute p. = 1.752. Molecular Refraction ( R )(5893 A.; 25' C.). R (calcd.) = 40.2; R (obsd.) = 45.7.
d 12.07 6.28 5.91 4.68 4.35 4.23 3.92 3.68 3.29 3.06 2.93 2.85 2 74 2.67 2.60 2.52
1/11
0 0 0 0
0 0
0 0
1 0 0 0
04 04 04 37 42 31 13 11 00 04 03 26
0 05
0 17 0 04 0 12
d 2.46 2.40 2.34 2.27 2.18 2.14 2.09 2.01 1.951 1,850 1 a21 1.778 1.729 1.640 1 571 1.533
1/11 0.07 0.06 0.04 0.04 0.04 0.04 0.07 0.05 0.04 0.04 0.02 0.02 0 02 0.04 0.02 0.02
FTJSIOX DATA. 4,6-DinitroresorcinoI sublimes readily t o give large well-formed crystals (Figure 1). Some of the crystals show an off-center optic axis interference figure mith 2V = 50°( +) and strong inclined dispersion, r > v . On further heating melting occurs with slight decomposition a t 215' C. The melt solidifies spontaneously in large areas of uniform orientation separated by large gas bubbles (Figure 3). The shrinkage cracks are very characteristic. Crystals showing the "hour-glass" type of crack give a B z , figure; crystals showing the straight cracks show an off-center optic axis figure.
V O L U M E 2 4 , N O . 12, D E C E M B E R 1 9 5 2 lcI.v:-li(”
-Ij‘
..”.,\
-:
2009
-,
Research and Development during World War 11. Alfred T. Blomquist was technical representative of OSRD Section B-!-A supervising progress of this work. Sien-Moo Tsang and John H. Andreen were also associated with this project and contributed to the above description. CONTR~BUTIONB of crystallographic data f o r this seotmn should be sent to Walter C. MoCrone, Analytical Section, Armour Research Foundation of Illinois Institute of Technology,Chicago 16,Ill.
Figure 1. Crystals of 4,6-DinitroresoreinoI by S u b l i m a t i o n
Reliability of Photoelectric Photometry SIR: I n the article “Reliability of Photoelectric Photometry” [Gridgeman, N. T., ANAL.CHEM.,24, 445 (1952)l reference is made to an equation presented by Stearns (Stearns, E. I., “Analytical Absorption Spectroscopy,” M. G. Mellon, ed., page 338, equation 7.11, New York, John Wiley & Sons, 1950) with the implication that the equation involves the statistically abhorrent simple addition of errors. This implication is incorrect. In Gridgeman’s article, the Martens photometer is not treated a t all; the article deals only with the situation in which the error in reading the transmittance is considered t o be constant over the entire transmittance scale. The familiar form of the error equation is
c
Gridgeman points out that if the error in setting the 100% line, considered t o be equal in magnitude to the error in the test reading, is taken into consideration, the equation becomes
re 2.
Orthographic Projection of Typical Crystal of 4,6-Dinitroreso,reinol
cD/D ~=~ OT
of 4,6-dinitroresoreinoI grow into thymol elongated D. The terminal angles itre all about 147‘. Iuterres between Bz. and the optic itxis are obtained. I
TInT
He also points out that if the errors of test reading and 100% line reading are not added under the radical, the iollowing abhorrent equation results,
ACKNOWLEDGMENT
the work described above was performed under a tween Cornell University and the Office of Scientific
(3) By the purest coincidence, this equation is practically identical in form with equation 7.11, which is CAS - T.log T8 -AC 1 T.
+
Figure 3.
4,6-DinitroresoreinoI f r o m Fusion
14) -, I
since ooncentration is proportional to absorbance. Gridgeman correctly implies that log should be written In in Equation 4. However, the two equations deal with two entirely different optical arrangements. Equation 4 corresponds to Equation 1, but deals with the specific ease of the Martens photometer which is governed by the laws of polarizing prisms. The (1+T,) factor in Equation 4 arises from a series of cancellations of trigonometric functions and not from any statistical reasoning, f d t y or otherwise. Incidentally, while the precision of setting the 100% line i s of importanoe in the type of instrument discussed by Gridgeman, i t is of no importance in the method of interpreting spectrophatometric curves recommended by Shurcliff and Stearns [J.Opt.
