., .1.
,
.,
.
6,.
. . ...
38. Potassium Permanganate, KMnO, Contributed by WALTER C. MCCRONE Armour Research Foundation, Illinois Institute of Technology, Chicago 16, 111.
HIS description represents the use of s n infrared eyepiece for Tthe determination of optical properties for a strongly ahsorb ing compound. Potassium permanganate is completely transparent a t 10,wO A., or more accurately perhaps in some wavelength range utilized by the 1-P-25 infrared image tube (72). Excellent cryatds of potassium permanganate can be obtained from water either in a beaker or on a microscope slide. These d a b were obtained with much greater ease through use of a trick t o change the crystal habit 80 that a. prineipsl view was shown directly. Gelatin in absorbed on the 100 face of potassium permmganite, 80 that thin plates lying on that face can be crystallized from a dilute aqueous gelatin solution. CRYSTAL MORPHOLOQY Crystal System. Orthorhombic. Form and Habit. P r i s m from water slightly elongated pam.ll.llel to c. The prisms are Figure 1. Crystals of Poclosed by the brachydome, tassium Permanganate (011 I When crystallized from from Water dilute aqueous gelatin tbjn loo plates are formed. Ob-sned through 1-P-25 infrared imsgo tube A x i d h t i o . a:b:c = 0.813: 1 :0.630. Interfacial Angles (Polar). 011 A oii = 760 54'; 110 A i i o = 78" 12'. X-RAYDIFFRACITON DATA Group. Vi" ( 1 ) . 11 Dimensions.. a = 7.394 A,, 6'= 9.098 A,, c 5.730 A,; a = 9.10 A, b = 5.60 A,, c = 7.40 A. (1). Formula Weights per Cell. 4. Formula Weight. 158.03. Densitv. 2.703:. 2.745 . (x-rav). . ..
p
d 5.72 4.54 3.85 3.70 3.54 3.42 3.20 2.93 2 R.R. ~
2 ',i 2.42 2 34 2.28
2.16 1 1* 1 VI 1.84
1.81 1.75
-
Prinaipd Line8 VI, d 0.21 1.73 0.50 1.71 0.21 1.68 0.35 1.83 0.90 1.59 0.35 1.53 1.00 1.50 0.82 1.48 O~S*
1 dR
0~3? Very weak Very weak
1.41
o nc.
0 F.5
Very weak U.11'
n
22 0.21 0 07
OPTICALP R O P E R ~ ~ S
i.ii 1.38
I .35 1.32
no
1 1.24
1 1 ~ 1
1.16
I 11
I/I, 0.18 0.15 0.15 Very weak 0.12 Very weak Very weak Very weak
.
.. .
.
.... L
Refractive Indexes (10,oOO A,; 25' C.) e = 1.765 * 0.005; 9 , = 1.78 * 0.01 (cslculated from e,y , 2V, and y,= 1.81 *
sip);
0.01. The refractive indexes a t 10,000 A. were etermned using ordinary immersion liquids and an infrared eyepiece (3). The refractive indexes of the liquids a t 10,000 A. were determined using an infrared eyepiece with an Abbe refractometer. It M worth noting that these liquids (Cargille) show almost no change in refractive index from 5893 to 10,oOOA. Optic Axial Angles (10,oM) A,; 25" C.). 2V = 80'. Optic Axial Plane. 100. Sign of Double Refraction. Positive. Acute Bisectrix. e.
c
F
Figure 2. Orthographic Projection of Typical Crystal of Potassium
Permanganate
PLEOCHROISM. Although potassmm wnnanmnate shows very stmng absorption in i l l ohntations, if ia ossrblble to me that absorption is strangest for light vibration par& to con very thin crystals. LlTERATURE CITED
(1) Bas& and Mark. Z. K v i l . , 64, 1-70 (1926). (2) Perrine snd MoCrone. Frontier, 12, No. 211 (1949). Coa~nreoiiolisof erystallograDhi0 data for this Seation should be sent to Walter C. McCrone, supervisor. Analytioal Section, Armour Research Foundation of the Illinois Institute of Technology. Chicago, Ill.
ConREcnoN. In the paper on phenylacetic acid [ANAL. CHEM., 22, 1338 (1950)1, the name of Donald G. Grabar was misspelled.
0 12
n ii
n
12
0 I3
very w r a l Very weak
0 12 Very weak Very weak Very w?ak v e r y weak
Refractive Indexes (red light; 25' C.) u = 1.80 * 0.02; y = 1.85 * 0.02. These two refractive indexes were obtained on very thin lying On 100 on a ~ c r o s c o p eslide from water containing about 1% gelatin. Even these very thin crystals showed very strong sbaorption and oh=rvation Of the Becke line was extremely difficult. No attempt was made to are thought to .he mes8uTe @, and the %bovevalues of e and *0.01 but may be -0.02.
Manual o f . Standardized Procedures for Spectrophotometric Chemistry. Harold J. Fister. 1st ed. 500 pages. Standard Scientific supply COrP.8 34 West Fourth St.9 New York 1% N. y.,1950. PriCe,$30. hi^ work might better be entitled "Directions for Selected Absorptiometric Clinical Methods." The objective of the author was "to collate under one cover a selection of methods adequate
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