AC BRIEFS

Data indicate that silazaned Chromosorb W most nearly approximates ... Kansas State University, Manhattan, Kan. Anal. Chem. 34, 1540 .... Dowex 1. X2 ...
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AC BRIEFS H i g h l i g h t s of t h e s c i e n t i f i c a n d t e c h n i c a l a r t i c l e s in t h i s i s s u e

Evaluation of S u p p o r t M a t e r i a l s f o r Use in G a s Chromatography Characteristics of various support materials and the ef­ fects of deactivating agents upon their absorption are investigated. Data indicate that silazaned Chromosorb W most nearly approximates an ideal support material. D. T. S A W Y E R a n d J . K. BARR, U n i v e r s i t y of C a l i f o r n i a , River­ side, Calif. A n a l . C h e m . 3 4 , 1518 ( 1 9 6 2 )

The Use of Lightly Loaded Columns in G a s Chromatography Minimum loading which can be tolerated for various supports without significant loss in efficiency is deter­ mined. Intercomparison of columns is more difficult than would appear since valid conclusions may only be drawn when all the variables are separately optimized rather than held equal. D. H . FREDERICK, B. T. M I R A N D A , a n d W . D. C O O K E , C o r n e l l U n i v e r s i t y , l+haca, Ν . Υ. A n a l . C h e m . 3 4 , 1521 ( 1 9 6 2 )

D e t e c t i o n and Identification of A l c o h o l s , Alkoxy G r o u p s , Lignin, and W o o d by G a s Liquid Chromatography A procedure is described for the conversion of alkoxy groups and alcohols to the corresponding iodides. T h e iodides are separated by G L C using silicone gum rubber on Chromosorb Ρ for column packing, and a strontium-90 ionization detector. K. F. SPOREK a n d M. D . D A N Y I , O w e n s - I l l i n o i s T e c h n i c a l C e n t e r , T o l e d o 7, O h i o Anal. C h e m . 34, 1527 ( 1 9 6 2 )

A c y l a t e d Cyclodextrins as Stationary Phases f o r C o m p a r a t i v e G a s Liquid C h r o m a t o g r a p h y i8-Cyclodextrin acetate, propionate, butyrate, and valerate are used as stationary phases for GLC of α-olefins, alcohols, aldehydes, esters, aldehyde-esters, and diesters. T h e heat stability of j3-cyclodextrin esters makes them suitable for comparative G L C . H E R M A N N SCHLENK, J. L GELLERMAN, University of M i n n e s o t a , A u s t i n , Minn.

a n d D. M.

SAND,

A n a l . C h e m . 3 4 , 1529 ( 1 9 6 2 )

S e p a r a t i o n and D e t e r m i n a t i o n of Mono-, Di-, and T r i p e n t a e r y t h r i t o l b y P r o g r a m m e d Temperature Gas Chromatography Polyhydric alcohols are converted quantitatively to the acetate esters by direct treatment with acetic anhydride. The reaction mixture is separated using temperature pro­ gramming techniques on a parallel dual column gas chromatographic system. D. S. W I E R S M A , R. E. H O Y L E , a n d H A N S REMPIS, C h e m i c a l C o . , Ltd., E d m o n t o n , A l b e r t a , C a n a d a

O b s e r v a t i o n s on t h e Effects of T e m p e r a t u r e , S u p p o r t , and Amount of Partitioning Liquid in G a s C h r o m a t o g r a p h y Four ketones are used to show how the adverse effect of a decrease in amount of liquid phase can be counteracted by a decrease in column temperature. Experiments using Teflon, crushed Vycor, glass beads, and Chromosorb Ρ and a constant volume of partitioning liquid indicated that relative efficiencies of columns, even when lightly loaded, may change radically with liquid loading as well as nature of the support. J . W . A S H L E Y a n d C . N . REILLEY, University o f N o r t h C a r o l i n a , C h a p e l H i l l , N . C , a n d P. H U R W I T Z a n d L. B. R O G E R S , M a s s a ­ c h u s e t t s Institute of T e c h n o l o g y , C a m b r i d g e 3 9 , M a s s . A n a l . C h e m . 3 4 , 1537 ( 1 9 6 2 )

G a s C h r o m a t o g r a p h i c A n a l y s i s of H e a d G a s of Dilute A q u e o u s Solutions

Space

Method for the separation and identification of volatile organic compounds at concentrations of 1 p.p.m. or less is given. Identification technique utilizes new selective reagents and permits the direct chromatographic analysis of trace volatiles of biological fluids. R I C H A R D BASSETTE, S U H E Y L Â O Z E R I S , a n d C . H . W H I T N A H , Kansas S t a t e U n i v e r s i t y , M a n h a t t a n , Kan. Anal. C h e m . 34, 1540 (1962)

G a s C h r o m a t o g r a p h y of P y r o l y t i c P r o d u c t s of Purines and Pyrimidines A simplified technique of pyrolysis is used for the microgram range which gives rapid, reproducible results for nonvolatile materials. Temperature of pyrolysis is 1100° to 1200° C. and a gas chromatograph with hydrogen flame ionization detector is used. E. C . J E N N I N G S , Jr., a n d K. P. DIMICK, W i l l t e n s Instrument & R e s e a r c h , Inc., W a l n u t C r e e k , C a l i f . A n a l . C h e m . 3 4 , 1543 ( 1 9 6 2 )

G a s C h r o m a t o g r a p h i c A n a l y s i s of 17H y d r o x y c o r t i c o s t e r o i d s b y M e a n s of Their Bismethylenedioxy Derivatives Formation of the B M D derivatives of hydrocortisone and other hydroxylated analogs results in a useful chromatogram. T h e method offers several advantages over the analysis of cortisone by the acetate or the pyrolysis product. M. A. KIRSCHNER and H e a l t h , B e t h e s d a 14, M d .

H.

M.

FALES,

National

Anal. Chem. 34,

Institute 1548

of

(1962)

Canadian

A n a l . C h e m . 3 4 , 1533 ( 1 9 6 2 )

Elution Behavior of N a t u r a l l y O c c u r r i n g Ninhydrin-Positive C o m p o u n d s during Ion Exchange C h r o m a t o g r a p h y

Thiol acetates are prepared using acetic anhydride as the acylating agent in the presence of an excess of triethylamine. T h e water-washed and dried product is separated chromatographically by using polypropylene sebacate on acid-washed Chromosorb W.

Common automatic analysis techniques are used to study behavior of naturally occurring nitrogenous compounds. Absolute identification is based upon independent criteria including isolation of the compound responsible for a peak, followed by chemical and physical characterization, paper chromatography, and ion exchange procedures. The danger of premature identification of peaks found in the analysis of nonprotein fractions is emphasized.

P. P. C R O I T O R U a n d R. W . F R E E D M A N , C o n s o l i d a t i o n C o a l C o . , Library, Pa. Anal. C h e m . 3 4 , 1536 ( 1 9 6 2 )

R. M . Z A C H A R I U S a n d E. A . TALLEY, Eastern R e g i o n a l R e s e a r c h L a b o r a t o r y , P h i l a d e l p h i a 18, Pa. A n a l . C h e m . 3 4 , 1551 ( 1 9 6 2 )

Q u a n t i t a t i v e G a s Liquid C h r o m a t o g r a p h y of T h i o c r e s o l s and Thioxylenols a s A c e t a t e Esters

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BRIEFS Tri-n-octylamine a s Liquid Anion Exchanger f o r C h r o m a t o g r a p h i c S e p a r a t i o n of Rare Earths on P a p e r or C e l l u l o s e P o w d e r Rare earth elements are separated by paper chromatog­ raphy using tri-n-octylamine impregnated paper and eluting with lithium nitrate. Rp values are recorded for sev­ eral rare earths with respect to eluent concentration. Milligram quantities of rare earths m a y be separated on cellulose powder treated with tri-n-octylamine.

S e p a r a t i o n of T e r p e n e H y d r o c a r b o n s b y G a s Liquid C h r o m a t o g r a p h y Utilizing C a p i l l a r y Columns and Flame Ionization D e t e c t i o n Apparatus descriptions and column preparation procedures are provided. Order of elution ia discussed as a function of the relative polarizabilities of the terpenes. D a t a indi­ cate that the stationary liquid phase is the most signifi­ cant operating parameter. R. A . B E R N H A R D , U n i v e r s i t y of C a l i f o r n i a , D a v i s , C a l i f .

C O R R A D O TESTA, C e n t r o Informazioni S t u d i Esperienze, M i l a n , Italy Anal. C h e m . 34, 1556 ( 1 9 6 2 )

Use of C o u n t e r c u r r e n t Distribution in t h e Q u a n t i t a t i v e A n a l y s i s of t h e A l k a l o i d s of C o m m e r c i a l Veratrine A series of countercurrent distributions is utilized to separate the major alkaloidal components of the mixture, thus facilitating a quantitative estimation of the minor constituents by application of the mathematics of countercurrent distribution.

Anal. Chem. 34, I576 ( I 9 6 2 )

Fundamentals of C o u l o s t a t i c A n a l y s i s . Experimental Results f o r t h e 1 0 s t o 10 7 Mole p e r Liter Range The hanging mercury drop is used experimentally t o verify the theory of the coulostatic electroanalytical method. The principal of the method is given as a three-dimen­ sional plot. PAUL DELAHAY and YASUSHI Baton R o u g e , La.

IDE, Louisiana S t a t e

University,

A n a l . C h e m . 3 4 , 1580 ( 1 9 6 2 )

G . R. S V O B O D A , U n i v e r s i t y o f W i s c o n s i n , M a d i s o n , W i s . A n a l . C h e m . 3 4 , 1559 ( 1 9 6 2 )

S e p a r a t i o n of M e t a l s b y C a t i o n Exchange in A c e t o n e - W a t e r - H y d r o c h l o r i c Acid Differences in distribution coefficients of metal ions are greater in acetone-water media than in aqueous media of the same hydrochloric acid concentration. Separations of cobalt(Il)-manganese(II), iron(III)-copper(II)-zinc(II), and c o p p e r d l ) - c o b a l t ( I I ) are reported. J . S. FRITZ a n d T. A . RETTIG, Iowa S t a t e U n i v e r s i t y , A m e s , Iowa Anal. C h e m . 34, 1562 ( 1 9 6 2 )

Mercury-Film E l e c t r o d e f o r Precision V o l t a m m e t r y Preparation and properties of an electrode which can be constructed from commercially available materials and used in conjunction with standard polarographic equip­ ment are discussed. T h e versatility of the electrode is such as to possibly permit its use in chronopotentiometry and microcoulometry, as well as for the techniques studied here. S. A . M O R O S , A m e r i c a n C y a n a m i d C o . , Bound Brook, N . J . Anal. C h e m . 3 4 , 1584 ( 1 9 6 2 )

A n o d i c V o l t a m m e t r y and EPR S t u d i e s of Isomeric P h e n y l e n e d i a m i n e s D a t a obtained at carbon paste electrode provide analyti­ cal information and details of oxidation mechanism. Prac­ tical analysis of phenylenediamine mixtures by stationary electrode voltammetry is not recommended.

D e t e r m i n a t i o n of S o r b i t o l a s Its H e x a c e t a t e by G a s Liquid C h r o m a t o g r a p h y Using an Ionization D e t e c t o r Reliable method for the quantitative determination of sor­ bitol in mixtures is presented. Use of mannitol as an inter­ nal standard minimizes the deficiency of variable detector response. Experimental error of less than 1% is possible. J . A . H A U S E , J . A . H U B I C K I , a n d G . G . H A Z E N , Merclc & C o . , Inc., D a n v i l l e , Pa. A n a l . C h e m . 34, 1567 ( 1 9 6 2 )

C h r o m a t o g r a p h i c S e p a r a t i o n of P e p t i d e s on Ion Exchange Resins. S e p a r a t i o n of P e p t i d e s from Enzymatic H y d r o l y z a t e s of t h e α, β, a n d y Chains of Human H e m o g l o b i n s Complex mixtures of peptides in protein hydrolyzates are separated by chromatographing first on the cation ex­ changer Dowex-50 and rechromatographing on the anion exchanger Dowex-1. Procedure is applied to the separa­ tion of peptides from human hemoglobins A and F . W . A . S C H R O E D E R , R. T. J O N E S , J E A N C O R M I C K , a n d KATHLEEN M c C A L L A , C a l i f o r n i a Institute of T e c h n o l o g y , Pasa­ dena, Calif. Anal. C h e m . 3 4 , 1570 ( 1 9 6 2 ) ·< Circle No. 131 on Readers' Service Card

H . Y. LEE a n d R. N . A D A M S , University o f Kansas, L a w r e n c e , Kan. A n a l . C h e m . 3 4 , 1587 ( 1 9 6 2 )

N o n a q u e o u s P o t e n t i o m e t r i c Titration of A c y l a m i d i n e s and R e l a t e d C o m p o u n d s Rough kinetic measurements in reactions of very weak acids and bases can be obtained by this method. Deter­ minations are achieved by successive titrations with hydrochloric acid and with tetrabutyl ammonium hydroxide. B. H . B E G G S a n d R. D . S P E N C E R , M e l l o n Institute, P i t t s b u r g h 13, Pa. Anal. C h e m . 34, 1590 ( 1 9 6 2 )

Instrumentation f o r t h e A u t o m a t i c S i m u l t a n e o u s M e a s u r e m e n t of m, t, w, and Drop C o u n t of a Dropping E l e c t r o d e Design, calibration, and evaluation aspects are discussed. Value lies in the determination automatically, simul­ taneously, and rapidly of certain of the data necessary for polarographic investigations. H . P. R A A E N a n d H . C . J O N E S , O a k R i d g e N a t i o n a l L a b o r a t o r y , O a k R i d g e , Tenn. A n a l . C h e m . 3 4 , 1594 ( 1 9 6 2 )

VOL. 3 4 , N O . 1 2 , NOVEMBER 1 9 6 2

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BRIEFS The Q u a n t i t a t i v e S e p a r a t i o n of Plutonium from Various Ions by Anion Exchange Plutonium(IV) is adsorbed from 7.2M nitric acid onto Dowex 1 X2 resin; other metals washed away with same molar acid. Plutonium is eluted with 0.36M hydrochloric— 0.01M hydrofluoric acid mixture. Average recovery is 100.007c of plutonium with standard deviation of 0.048% for known solutions. I. K. KRESSIN and G . R. WATERBURY, Los Alamos Scientific Laboratory, Los Alamos, Ν. Μ. Anal. Chem. 34, 1598 (1962)

S o l v e n t Extraction Method f o r t h e R a d i o c h e m i c a l Determination of Chromium The procedure involves a preliminary hydrolytic separa­ tion of chromium(III), oxidation to chromium(VI), and extraction from hydrochloric acid of the tctrabutylammonium chromium(VI) ion-association complex into methyl isobutyl ketone. Chromate is stripped from the organic phase with base and yield is determined spectrophotometrieally. W . J . MAECK, M. E. KUSSY, and J. E. REIN, Phillips Petroleum Co., Idaho Falls, Idaho

A u t o m a t i c Infrared A n a l y s i s of Polymer Films An automated infrared spectrophotometer is provided with a digital readout for conversion of infrared absorption to concentration on a digital computer. System allows change from one analytical procedure to another by chang­ ing a single program sheet. Instrument is used for routine analysis of polymer films from laboratory and pilot plant. D. R. J O H N S O N , J . W . CASSELS, E. G. BRAME, and D. F. WESTNEAT, E. I. du Pont d e Nemours & Co., Wilmington, Del. Anal. Chem. 34, 1610 (1962)

Rapid N o n d e s t r u c t i v e Determination of Beryllium Using Van d e Graaff X-Rays X-rays impinge on a beryllium-containing sample giving off neutrons according t o the Be (7, n) 2a reaction. Neu­ trons captured in a silver disk produce radioactive silver isotopes which are counted with Geiger-Muller apparatus. Determination time averages 4 minutes. C. A. LEVINE and J. P. SURLS, Jr., The Dow Chemical Co., Pittsburg, Calif. Anal. Chem. 34, 1614 (1962)

Anal. Chem. 34, 1602 (1962)

C o n d e n s a t i o n Nuclei, a N e w Technique for G a s Analysis Plutonium S u l f a t e T e t r a h y d r a t e , a P r o p o s e d Primary A n a l y t i c a l S t a n d a r d f o r Plutonium Stoichiometric compound, prepared by controlled crystal­ lization from sulfuric acid solution, appears to meet the requirements for a primary standard. Advantages include ease of preparation, analysis, and storage. C. E. PIETRI, U. S. Atomic Energy Commission, New Brunswick, N.J.

A general description of the technique is included, along with possible instrument configurations and performance test data. Application to air pollution control, toxic vapor detection, and continuous monitoring of chemical processes is envisioned. F. W . VAN LUIK, Jr., and R. E. RIPPERE, General Electric Co., Schenectady, Ν. Υ. Anal. Chem. 34, 1617 (1962)

Anal. Chem. 34, 1604 (1962)

G e n e r a l X-Ray S p e c t r o g r a p h s Solution Method f o r A n a l y s i s of Iron-, Chromium-, a n d / o r Manganese-Bearing Materials Determination of Tantalum in Tungsten by Activation Analysis Neutron activation is used for a rapid and simple analyti­ cal method in range 0 . 1 % to 10% tantalum in tungsten. Concentration ranges are not limited by the technique, which requires no chemical manipulations. RICHARD N.J.

CORTH,

Westinghouse

Electric

Corp.,

Bloomfield,

The procedure is applied to manganese and chromium alloys, slags and ores, Alnico, steels, and refractories for combinations of iron, chromium, manganese, nickel, copper, and cobalt. A single calibration system per ele­ ment serves for all materials and acid matrices. B. J . MITCHELL and H. J . O'HEAR, Union Carbide Metals Co., Niagara Falls, Ν. Υ. Anal. Chem. 34, 1620 (1962)

Anal. Chem. 34, 1607 (1962)

Determination of G a s e o u s Fluorine Using R a d i o a c t i v e C l a t h r a t e s

Determination of Molecular W e i g h t of P o l y e t h y l e n e s with an O s c i l l a t i n g Ebulliometer

Fluorine is reacted with a radiochemical bed, quinolkrypton-85 clathrate and undergoes a gas exchange reac­ tion. The method which uses conventional counting tech­ niques can be adapted to routine gas monitoring.

Number-average molecular weights of polyethylenes and polyethylene fractions up to 20,000 are determined with an apparatus improved by using highly sensitive thermis­ tors and better controlled temperature. Upper limit of measurable weight is set by superheating of the polymer solution.

C. O . HOMMEL, F. J . BROUSAIDES, and R. L. BERSIN, Tracerlab, Waltham 54, Mass.

J. E. BARNEY, II, and W . A. PAVELICH, Spencer Chemical Co., Merriam, Kan.

Anal. Chem. 34, 1608 (1962)

Anal. Chem. 34, 1625 (1962) VOL. 34, NO. 1 2, NOVEMBER 1962

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BRIEFS Determination of Parts p e r Billion Iron b y F l u o r e s c e n c e Extinction

Determination of C a r b o n Monoxide under Reduced Pressures Method is based on the oxidation of carbon monoxide by iodine pentoxide, Ditte's reaction. Applicable t o the prob­ lem of determination of small amounts of carbon mon­ oxide at low partial pressures in the presence of nitrogen, oxygen, and/or hydrogen. M E N A C H E M STEINBERG, A B R A H A M G L A S N E R , LEVY, The H e b r e w University, J e r u s a l e m , Israel

and

EZRA

The fluorescence intensity of aluminum-Pontachrome Blue Black R complex decreases in the presence of iron. The fluorescence decrease is linear in the concentration range of 0.02 to 0.2 μg. of iron per ml. of final solution. J A C O B BLOCK a n d EVAN M O R G A N , O l i n M a t h i e s o n C h e m i c a l Corp., New Haven, Conn. A n a l . C h e m . 3 4 , 1647 ( 1 9 6 2 )

A n a l . C h e m . 3 4 , 1629 ( 1 9 6 2 )

An NMR S t u d y of t h e P r e c i p i t a t i o n of M a n g a n e s e Sulfide from H o m o g e n e o u s Solution Critical supersaturation of manganese sulfide in aqueous solution is studied by nuclear magnetic resonance. T h e method depends on the effect of paramagnetic ions on the water proton magnetic resonance relaxation times. R. L. C A U S E Y a n d R. M. M A Z O , C a l i f o r n i a Institute of T e c h ­ nology, Pasadena, Calif. Anal. Chem. 34, 1630 ( 1 9 6 2 )

C o m p a r i s o n of t h e R e a c t i o n s of Amidinourea and Amidinothiourea with Various Metal Ions Salts of 20 metals were tested with amidinourea and amidinothiourea. Salts of nickel, copper, cobalt, silver, and palladium formed soluble or insoluble derivatives. The derivatives, prepared in quantity, were analyzed to determine the mole ratio of the metal to amidinourea or amidinothiourea. R. H . TRIMBLE, 121 M e a d o w Lane, Kingsport, Tenn. A n a l . C h e m . 3 4 , 1633 ( 1 9 6 2 )

Determination of O x y g e n in Mixed Fluorides b y Inert G a s Fusion Method has advantages of speed, simplicity, and con­ venience of analysis. Innovations include sample prepara­ tion techniques, elimination of platinum flux, and use of a water and acid trap t o remove volatilized fluorine compounds.

S e m i m i c r o and Micro S t e a m Distillation. The Estimation of t h e Essential Oil C o n t e n t of Small Plant S a m p l e s Micro steam distillation technique is used for determining the volatile oil content of small plant materials. Two micro units and one semimicro unit are designed which give accurate results comparable with macrotechniques. The three units, used as a group, enhance the purification of small quantities of organic liquids. W . J . F R A N K L I N a n d H . KEYZER, M u s e u m of A p p l i e d Arts a n d Sciences, Sidney, N e w South W a l e s , Australia A n a l . C h e m . 3 4 , 1650 ( 1 9 6 2 )

A c i d - B a s e Indicators in t h e Binary S o l v e n t , Acetic Anhydride-Acetic Acid The composition effect of acetic anhydride-acetic acid mixtures upon the half-neutralization number (pLVO is determined for indicator bases: acridine orange, brilliant green, rhodamine B, and thioflavine T. Rhodamine Β proves to be a suitable indicator for the photometric titration of leveled and intermediate bases with perchloric acid in the mixed nonaqueous solvent containing 70% ( v / v ) acetic anhydride. O. W . KOLLING W i n f i e l d , Kan.

a n d T. L. STEVENS,

Southwestern

College,

A n a l . C h e m . 3 4 , 1653 ( 1 9 6 2 )

J . L. POTTER, J . E. M U R P H Y , a n d H . H . H E A D Y , U . S. D e p a r t ­ ment o f t h e Interior, Reno, N e v . A n a l . C h e m . 3 4 , 1635 ( 1 9 6 2 )

A c t i o n of Perchloric Acid and Perchloric A c i d Plus Periodic A c i d on Ammonia and Amino Nitrogen The successful destruction of organic matter with a mix­ ture of periodic acid and perchloric acid suggested an adaptation of this method to the determination of amino nitrogen. This digestion is suitable for the wet oxidation of organic materials b u t does n o t furnish a generally applicable method for the determination of nitrogen.

Determination of Alkyd and Monomer-Modified Alkyd Resins by A t t e n u a t e d Total R e f l e c t a n c e Infrared S p e c t r o m e t r y Quantitative analyses of phthalie anhydride, isophthalic acid, vinyl toluene, and styrene are described. Method is developed for routine analysis and does not require prior chemical treatment. R. L. H A R R I S a n d G . R. S V O B O D A , F r e e m a n C h e m i c a l C o r p . , Port W a s h i n g t o n , W i s . A n a l . C h e m . 3 4 , 1655 ( 1 9 6 2 )

F. B. M O O R E a n d H A R V E Y DIEHL, Iowa S t a t e University, A m e s , Iowa A n a l . C h e m . 3 4 , 1638 ( 1 9 6 2 )

A S e r i e s of P r o c e d u r e s f o r Determining Boron in α W i d e V a r i e t y of O r g a n o b o r o n C o m p o u n d s Titration with N a O H in the presence of a large excess of mannitol completes all of the six procedures described. Difficulties due to a lack of sensitivity at beginning and end points were eliminated by selection of appropriate oxidation procedures. R. H . P I E R S O N , U . S. N a v a l O r d n a n c e Test S t a t i o n , C h i n a L a t e , Calif. A n a l . C h e m . 3 4 , 1642 ( 1 9 6 2 )

Indirect S p e c t r o p h o t o m e t r i c Determination of Zinc and C o b a l t Using Eriochrome Blue Black R Zinc and cobalt in mixtures are determined by an indirect spectrophotometric technique. The metal ions are complexed with Eriochrome Blue Black R and the absorbance recorded at 625 ταμ. E D T A is added which selectively combines with the zinc ion and the absorbance is measured again. Cobalt concentration is calculated directly and zinc concentration is calculated by absorbancy difference. A n a l . C h e m . 3 4 , 1657 ( 1 9 6 2 )

V O L 3 4 , N O . 1 2 , NOVEMBER 1 9 6 2

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