V O L U M E 2 7 , NO. 11, N O V E M B E R 1 9 5 5
1841
In addition to tetrathionate, the higher polythionates also react with cyanide to form thiocyanate.
+ 5CN- + H20 =
SsOs--
+ 4CN- + Hz0 =
SsOs--
S203-S203--
+ SO4-- + 2 H C S + 3CSS+ Sod-- + 2HCN + 2CSS-
Therefore the method as developed is suitable for the three polythionates, although each ion will interfere in the deterrnination of the other. In practice, it is probable that all three ions nill exist to some degree in any sample suspected to contain polythionates. As any thiocyanate in the liquor is a serious interference] in the recommended procedure a sample blank is prepared by adding the reagents in such a manner that tetrathionate is not converted to thiocyanate. Robinson measured the sample against the sample blank, but this procedure required norking with a variable slit width. In the recommended procedure both the sample and sample blank are measured against a reagent blank a t constant slit width. The difference in absorbance is proportional to the tetrathionate concentration Test of Method. Neither standard samples nor an independent method of analysis of sufficient sensitivity was available to test the method. Therefore, it was decided to add various amounts of a standard tetrathionate solution to a solution of unknown tetrathionate composition and attempt to determine the added tetrathionate accurately. Several 10-nil. aliquots of a liquor known to contain tetrathionate, with and without 0.05 to 2.5 nig. of added tetrathionate, were analyzed by the recommended procedure using both 1-cm. and IO-cm. absorption cells. The absorbance obtained for an aliquot containing no added tetrathionate was subtracted from the absorbance obtained on the other aliquots. From these corrected values the amount of tetrathionate ion found was calculated. In these calculations an absorbance index obtained by passing pure solutions over the ion exchange resin (1.4% lower than the value reported in Table 11) was employed. An average error of only 1% was observed between the amount of tetrathionate added and recovered (Table 111). The general
Table 111. Test of Method Tetrathionate Added, M g .
Error,
Tetrathionate Found, M g 1-Cm. Cells 0.501 1 01 1.51 2.00 2.48
0,500 1.00 1.50 2.00 2.50
70
+0.2 +1.0 +0.7 0.0 -0.8
10-Cm. Cells 0.0.50 0.100 0 . 150 0.200 0.250
0.049 0.097 0.150 0.197 0.245 .iY.
-2.0 -3.0 0.0 -1.5 -2.0 rl 0
tendency for the answers to be slightly low seems to indicate some holdup of the tetrathionate on the resin. If the calibration curve is obtained by passing pure solutions over the ion e.rchnTige columns in the same manner as the samples are to be treatetl, this holdup of tetrathionate should be automatically combensated for. LITERATURE CITED
Furness W. and Davies, W.C., Analynt, 77, 6 9 i (19.X). Jay, R.R., A N ~ LCHEM., . 25, 288 (1953). Mellor, J. W., ”Comprehensive Treatise on Inorganic and T1:ecretical Chemistry,” vol. 10, p. 617, Longmans, Green, L O I ~ L ! ~ ~ , 1930. hlurayama, T., J . Chem. SOC.Japan, Picre Chem. Sect., 7.!, ::A9 (1953). Robinson, R. E., unpublished data Sandell, E. B., “Colorimetric Determination of Traces of Sletals,” 2nd ed., p. 367, Interscience, New York, 1953. RECEIVED for review M a y 15, 1955. Accepted August 10, 1955. The T!aw Materials Development Laboratory is operated by t h e Kational Lead Co., Inc., for t h e Atomic Energy Commission. Work carried o u t under Contract S o . AT!49-6)-924.
CRYSTALLOGRAPHIC D A T A
100. Procaine Penicillin G H A R R Y A. ROSE, Lilly Research Laboratories, Indianapolis 6, Ind.
C&
CH3
CI~I-~-CII-COOH.CtHpN-CH*CH20C-
0 11
I I N \ /\
s
CH
C=O
\d Structural Formula for Procaine Penicillin G ROCAINE penicillin G is a salt of penicillin which is highly ‘insoluble in water. The compound has found great use in medicine, but the crystallography has been very incompletely described. Crystals suitable for crystallographic work may be obtained by slow evaporation of methanol-n-ater solutions (Figure 2). Good crystals may also be obtained by slow mixing of aqueous solutions of procaine hydrochloride and sodium penicillinate. The crystals obtained from methanol-water n-ere exception-
X-Ray Powder Diffraction Data d 13.83 9.49 8.38 7.38 7.03 6 50 7 95 5 6 .. 7 5.55 5.22 4.90 4.71 4.62 4.47 4.27 4.12 3.68 3.51 3.38 3.28 3.16 3.12 3.03 2.954 2,888 2.793 2.701 2.582 2.459 2.334 2.281 2.078 2.050 2.022
r/r1 0.33 0.27 0.33 0.13 0.27 0.13 0 . 05 73 0.20 0.67 0.20 0.97 1 .00 0.07 0.13 0.53 0.33 0.27 0.33 0.33 0.07 0.07 0.07 0.07 0.03 0.07 0.03 0.03 0.20 0.03 0.03 0.03 0.03 0.03
hkl 100 001 110 111 011 lOL
d(Ca1cd.) 13.92 9.54 8.37 7.3G 7.05 6.60
210 211 111 020 120 002 311, 500 302 221 312 32i. 225 320 130 313
56.07 .80 5.58 5.23 4.90 4.77 4.66,4.64 4.50 4.28 4.13 3.69,3.68 3.47 3.39 3.28
ANALYTICAL CHEMISTRY
le42
ally clear, and interfacial angles calculated from x-ray data were checked against those measured optically using the Unicam rotation x-ray camera as a single circle goniometer with results a8 noted in the crystal morphology section.
Density.
1.255 grams per cc. (displacement and flotation),
1.256 gramsper ec. (x-ray).
Space Group. C? - P2$ (based on the facts that the only regular x-ray extinctions show OkO present only when k = 2n and that the external morphology is obviously hemimorphic). OFTICALPROPERTIES Refractive indices. a = 1.545, p = 1.570, y = 1.685 ( 1 ) . a' (in 100) = 1.546, y'(in001) = 1.610. Optic Axial Angle. 2V = 52" (calculated from n,8, and y). Optic Axial Plane. 010. Acute Bisectrix. y. Optic Sign. Positive(1). Extinction, n A e = 15'inacuteB.
C
r 001
Figure 1. Orthographic projection of procaine penicillin G
The x-ray powder diffraction dat.a were obtained using v a n e dium-filtered chromium radiation and a camera 114.6 m. in diameter. A wave-length value of 2.2896 A. was used in the caloulations. CRYSTAL MORPHOLOQY Crystal System. Monoclinic hemimorphic. Form and Habit. Massive crystals elongated parallel to the b axis and lying either an the 100 or 001 faces. The usual forme me the orthopinacaid (loo}, basal pinacoid (001); right prism (1101 with left positive monoclinic sphenoid (111) and right clinodome (011) cr left prism { llO} With rjght negative monoclinic sphenoid { 111 1 and left clinadome (011 }; and the positive hemiorthodome { 10T). Axial Ratio. a : b : c = 1.491:1:1.022 (x-ray). Interfacial Angles (Polaz). 110 A 2 1 0 f 73'54' (calculated x-ray), 73" 54' (observed optical). 111 A 111 = 90' 40' (calculated x-ray), 90" 24' (observed optical). 101 A 001 = 41138' (calculated x-ray), 41" 42' (observed optical). 011 A 011 = 95" 20'. Beta Angle. 116' 56'. X-RAY DIFFRACTION DATA Cell Dimensions. a. = 15.61 A., bo = 10.47 A., co = 10.70A. Formula Weightsper Cell. 2. Formula Weight. 588.71.
Figure 2.
Crystals of procaine penicillin G
Recrystallized from methanol-water on mioroneope &de
FUSIONBEHAVIOR.Procaine penicillin G melts in the range 106" to 110" C. with decomposition. The melt does not crystallize on cooling. LITERATURE CITED (1) Tillson, A. H.. and 760-7 (1954).
Eisenberg, W. V., 6.Am. Phann. Amoc., 43,
C o m m s m r o ~ of s orystdlogrsphic data lor this aection should be sent to Welter C. MoCrone, Analytical Section, Armaur Research Foundation of Illinois Institute 01 Technology, Chicago 16, Ill.
SCIENTIFIC C O M M U N I C A T I O N
Determination of Minute Traces of Water by Use of Methylene Blue
physical constants have been used, such as the measurement of specific gravity for the determination of water in alcohols; the measurements of electrical conductivity, refractive index, viscosity, and critical solution temperature; centrifugation for suspended moisture; measurements of heat of hydration, dew point, heat of dilution in sulfuric acid, and pressure differential after exposure to lithium chloride; and near infrared absorption spectra. Other methods involve condensation into a tared cold trap, where the water is weighed, or into a buret, where the volume change is recorded. I n fuel gas, moistnre has been detected by the color change of cobaltous bromide on hydration. Water
