ANALYTICAL CHEMISTRY
914 a n d cheniical composition on htiuvtureP developed. G r a p h i t e formation is clmsified undei w v e n tvues : however, illustrations a r e not 111 terms of t h e .4STlI designation (A 2 4 7 4 7 ) n i t h which .4niericaii metallurgists a r e familiar. Photomicrographs a r e given at magnifications well chosen to reveal structures represented a n d a s h o r t description of each is given on a f a r i n g page. As at'tention h a s been confined to relatively f w "typical" structures. much of practical utility has
Cottrell : Samaritan of Science. F r a n k Camrun. 414 I):tgcy Doubledav and Co.. 5T5 >fadisoil I V C New . York 22 S Y.
$4.50. Dosages ~ ~ l p r h c i p e~s et ~ ~k t h ~~ d,-J. ~ ('h,a,lot ~~ . K. Gauguin. 243 pages. lIaeso11 e t Cie, 120 Boulevard Saint-Grrinaine, Paris, 6, France. Fr. 1500. Manometric Methods. Jfi.lnlrol,n Dizon. 3rd ed. C h n b t , i d g e ITniversit,yPress, 32 East 6Tth St., N e w York 22,S. Y. 82.00. JAMES \ITHL-RMAK -.
necessarily been omitted.
Congress of Practical Polarography
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N E W BOOKS
of Practical l'olarography, arranged by t h e Cent,ral Polarographic I n s t i t u t e of P r a g u e , was held F e b r u a r y 18 a n d 19, 1952, in Bratislava, Slovakia. .4bstracts of t h e papers presented are given here. 'HE Congress
INORGAKIC ANALYSIS
Polarographic Estimation of Gold in Biological Material (Urine) after Injections of Myochrysin. V. LINH-LRT. In aurotherapeutics after intramuscular injections of Myochrysin (aurous salt of thiomalic acid) a rertain part of the gold passes into t h e urine. The remainder of the gold is deposited in the organism and sometimes c-auaestoxicxymptoms. With information as the gold content of the urine, it is possible t o follov the course of the therapeutic proceeding and t o foresee undesirable vomplirations. Conditions are given under wliicli it i? possible to determine gold in urine polarographically from the hydroxide complex of trivalent gold. Organir depolarizers and rcduciug agents are removed from the evaporated residue by mean* of heat, after reduction of gold salts by hydrazine sulfate in acidic or by hydrogen peroxide ill alkaline medium. The residue after this operation is extracted by aqua regia and ronverted by 2 -Y potassium hydroxide t o the hydroxide complex of trivalent gold. Atmospheric oxygen is then removed with hydrogen. and the polarograI)hic m r v e of gold ic ohtained with a half-wave potential at - 0 . 5 8 volt, Polarometric Estimation of Silver. J . DOI.E&AL, V. H E N C LA, N D
I-,S I M O N . The reactioti mechanism of formation of the silver complex with ethylenediaminetetraacetic acid n-as studied both potentiometrically and polarographic~allyand its formula was derived. On the basis of these studies polarometric estimation of silver with a volumetric solution of potassium iodide in the presence of complexone I11 (the disodium salt of ethylenediaminetetraacetic acid) was worked out. using a platinum rotating electrode. I n this way t h e disturbing effect of adsorpt,ion was removed and the estimation of silver in the prer;ence of a number of metals-lead, copper, bism u t h , iron, cadmium, zinc, arhenic. antimony, and thallium--was made po6sible. Thi. method was used for estimarion of silver in practical samples. Polarographic Estimation of Copper with Diethyldithiocarbamate. -4. O K A ~\ND E. B R E . J ~ K O ~ , & .
By this method t h e concentration of copper(I1) in the solution is determined, which decreases on addition of diethyldithiocarbamate( D D T ) . I n aqueous and slightly acidic solutions the titration curves correspond to the equivalence of copper and D D T ; a t a n acidity over 0.5 S iii hydrochloric acid the relations are not more equivalent. probably because of the partial decomposition of t h e agent. Thia method permits t h e estimation of 0.2 mg. of copper with a n accurary of =t1.5%. The quantity of copper may he estimated also according to t h e decrease of the cathodic wave of copper which linearly depends on the amount of added D D T . The equivalence point, is determined by an empirical factor. D D T yields a t positive potentials a wave suitable for titration of this agent with copper. The wave of D D T disappears and the surplus of copper is indicated by the wave of copper. Simultaneous Polarographic Determination of Manganese and Iron in Iron Ores with an Alkaline Solution of Triethanolamine. " >
J. R I H . ~ The ~iolarographicheharior of triethanolamine vomylexes of man-
ganese and iron was reported by J. MojgiB a t the International Polarographic Congress. T h e well defined wares of manganese and iron in this medium were used for working out a method for simple and quick determination of these elements in iron ores and in waters. T h e disturbing effect of copper and lead was removed by reduction of these cations w i t h zinc dust in an acidic medium. This method was proved in many hundreds of practical analyses. Polarographic Estimation of Arsenic in Steel, Iron, and Ores. I,.
BRHAEEK. The estimation is based on isolation of arsenic by distilling it off in the form of arsenic trichloride or arsenic tribromide from a small amount of the dissolved bample. I n t h e distillate arsenic is oxidized with nitric acid to the nonvolatile pentavalent form, and the solution is then evaporated t o the concentration suitable for polarographic work. The reduction to trivalent arsenic, which yields a well defined wave in a medium of sulfuric acid and ethyl alcohol. is carried out with iodine and potassiunl pyrosulfite. Polarographic Estimation of Sulfur. A. TOCKSTEIN .\SD I,. S E ~ K .
A polarographic method for estimation of sulfur was worked out with the aid of coniplexorle 11: zCOOH HOOC.CHz
HOOC.CH/ CHzCOOH The sulfur present in the .,ample is courerted to sulfate ion and isolated as barium sulfate. Vor the estimation advantage is taken of the properties of a mixture of free silver ions with an excess of silver complex with ethylenediaminetetraacetic acid i n amnloniacal medium. This mixture yields two polarographic waves, the more positive corresponding to the concentration of free silver ions and t h e more negative being proportional t o the silver complexonate concentration. After barium sulfate is dissolved in an. ammoniacal solution of the silver complexonate containing a small amount of free silver ions, t h e more positive wave increases. This increase of the wave of free silver ions is caused by t h e formation of the barium complex with ethylenediaminetetraacetic acid, which is stronger than the silver complex, so t h a t a n equivalent amount of free silver ions is liberated. Thus, the change of the height of the first ware is proportional to the amount of the barium sulfate dissolved. T h e applicability of this method wa* proved on samples of ores aiid of India rubber with good results. Estimation of Small Amounts of Titanium in the Presence of Excess Iron and Other Elements. A. B I A ~ E K . I n a medium of hydrochloric or sulfuric acid and in the presence of hydroxylamine and sodium oxalate, tetravalent titanium yields a cathodic wave of kinetic character. The form and the height of this wave depend first of all on the p H of the solution, concentration of hydroxylamine, and temperature. I n strongly acidic medium a wave is to be observed with a half-wave potential of -0.280 volt 3s. the saturated calomel electrode. The height of this wave is proportional to the concentration and is suitable for analytical determination. T h e method is very sensitive, owing to the catalytic character of t h e electrode reaction. I n thia way small amounts of titanium may he determined in the presence of a surplus of trivalent iron which is reduced by hydroxylamine to the divalent form. T h e method mas proved on samples containing an excess offerric, chromic, manganese, and aluminum ions, and where the concentration of titanium was 5.18-6 to 8.10-8 M. T h e estimation is hindered by molybdenum and tuugJterl and by vanadium i i i great coilcentration.
~
i
V O L U M E 2 4 , NO. 5, M A Y 1 9 5 2
915
Polarographic Estimation of Magnesium with Oxyquinoline.
J.
PECHA N D 0. MIKL. T h e method for determining magnesium with oxyquinolirie, worked o u t by J. V. A. Norhk. was extended for quick estimation of 0.1 to 2.5 mg. of magnesium by ,measuring the wave height, of oxyquinoline in filtrates after precipitation of t h e magnesium salt. T h e method is carried out in t h e following way: 5 ml. of 0.57' solution of oxyquinoline in dilute acetic acid (1 to 100) is pipetted into a 25-ml. volumetric flask and a solution with 2.5 mg. of magnesium is added. T h e mixture is heated in warm water, 5 ml. of dilute ammonia (1 to 20) is added, and t h e precipitation is hastened by boiling for 5 minutes. After cooling, the solution is made u p t o the mark, t h e precipitate is filtered off on a d r y paper, and 0.3 ml. of 50% sodium hydroxide and 0.1 ml. of 0.5% gelatin are added. T h e polarogram of oxyquinoline ib recorded after bubbling nitrogen through the solution. Estimation of Some Divalent Metals by Titration of Ammonium in 5'. SIMON. Phosphates of the Type MeNH4POl.zH20. I. SEKERKA, m n J. DOLE~AL.
I n phosphates yielding compounds of the type MeNHdP04.rHD with some divalent metals-cadmium, manganese, zinc, and magnesium -ammonium and also those divalent metals or phosphates were determined by titration with a volumetric solution of calcium hypochlorate in the presence of potassium bromide (hypobromate "in the nascent state"). 111 order to maintain the phosphates in solution in the slightly alkaline medium in which the titratio[> is carried out, complexone 111 was used, which forms strong complexes with t h e cations mentioned, the ammonium remaining oxidizable. T h e estimation was carried out by polarometric titration with a platinum rotary electrode a t 0.0 volt short-circuited to the saturated calomel electrode. T h e end of the titration was indicated by a sudden increase of current which is proportional t o the concentration of the volumetric agent. I n a polarographic study of the reaction with the dropping mercury electrode, chloramine was used. The method proved useful in a great number of samples. A Polarographic and Polarometric Study of Palladium. V. SIMON.
T h e polarographic behavior of divalent palladium ions was studied in different electrolytes, looking toward the possibility of its separation from gold and silver. I n polarometric titrations different organic precipitating agents were used, such a s dimethylglyoxime, salicylaldoxime, oxine, and dimercaptobenzothiazole. -4s a volumetric agent an ethanolic solution of dimethylglyoxime was found t o be moat suitable. Tlie iiiterfering effect of other elements was studied. Polarographic Determination of Lead Corrosion.
J. H A N Z I ~ K .
-1new test for following lead corrosioii in concentrated sulfuric acid is based on t h e determination of sulfur dioxide a s a reaction product from the polarographic wave of sulfur dioxide. The effect of different factors such as temperature, preliminary surface preparation, stirring, placing of the sample under examination, presence of impurities, interfering elements, etc., on t h e reproducibility of t h e test was examined and optimal conditions were found. -1relation between the beginning of corrosion of the unprotected lead and t h e quality of t h e protecting film of lead sulfate was determined. Tlie corrosion of lead protected by the sulfate film was followed and it was found t h a t during 6 days the rate of corrosion changes in different ways characteristic of some impurities (artificially alloyed), such as copper, nickel, and calcium. From this changing corrosion course of differently alloyed leads it was possible t o explain some disarepanciea concerning d a t a on existing dipping tests and the flash test. A Criterion of Water in Lactamsulfuric Acid. Z. VEEhil.\.
In polarographic analysis of lactamsulfuric acid the presence of water is indicated by a wave of sulfur dioxide a t -0.5 volt. The hydrogen ions are reduced a t -1.3 volts. I n absence of water only hydrogen ions are reduced. Owing t o the considerable viscosity of the lactamsulfuric acid, t h e test is carried out a t +70° C. T h e polarographic vessel is placed in a glass jacket with circulating hot water. ORGANIC A N A L Y S I S
Polarometric Estimation of Cephaeline and Emetine. T. JUNGR..4ND J. Z i K A .
-1.JISOX.\,
T h e active alkaloids of Radix ipmcuanhae, emetine and cephaeline, react with p-diazobenzeIlesulforiic acid t o form a red dyestuff, This reuctioii may be used for polarometric estimation of both alkaloids. Tlle acid is polarographically reduced in two steps, while the azo
dyestuff is reduced in one wave a t considerably more negative potentials. By using a solution of p-diazobenzenesulfonic acid a s the titration agent, the linearly increasing first wave of the volumetric solution may be followed a t -0.3 t,o -0.4 volt when in excess after t h e equivalence point. I n this work t h e effect, of p H and temperature, and the time suitable for the quantitative course of the reaction was examined. On t h e basis of this study a method was worked out for estimation of emetine and cephaeline in tablets, injections. etc. I n the root and tincture of ipecacuanha these alkaloids may be estimated only after their separation. Attempts to estimate both alkaloids in their mixture on t h e basis of their different reaction rates with the titration agent in differently buffered solutions failed. For this purpose t h e following combination of polarographic and polarometric methods has proved t o be satisfactory: B y polarometric titration with p-diazobenzenesulfonic acid the sum of both alkaloids is determined arid then cephaeline is determined polarographically (see the next communication). From the difference the amount of emetine is calvulated. Polarographic Estimation of Cephaeline. J. Z+KA.
J I N D R A V. , JCSCR.
AND
T h e indirect polarographic nitrosation method, known from the determination of morphine, was used for estimation of cephaeline. Cephaeline, a s a substance of phenolic character, may be converted into a nitroso compound by treatment with nitrite in a n acidic medium. After the nitrosation is interrupted by an excess of alkali, the salt of the nitroso compound is reducible a t t h e mercury dropping electrode. Emetine, which ih the methoxy derivative of cephaeline, cannot be converted into a nitroso compound. In nitrosation t h e effect of temperature, time, stability of the nitroso compound, etc., wa3 followed. When emetine is in large excess over cephaeline, a precipitate is formed in t h e alkaline solution which hinders the determination. This difficulty was removed by adding methanol to the solution. T h e method was used for estimation of cephaeline in the root and tincture of ipecacuanha and for estimation of cephaeline traces in injection* and tablets with chloride of emetine. T h e method is sensitive enough for a reliable estimation of cephaeline as impurity in "Emetinum hydrochloricum-Merck." Polarographic Estimation of Some Phenylmercuric Compounds. V. V o J i I . Phenylmercuric compounds, in which the divalent mercury is joined to the carbon atom by a chemical bond, are reduced a t the dropping mercury electrode in two one-electron steps. The electroreduction proceeds over a free radical which dimerizes after its formation and crystallizes a t the electrode surface. This crystallization causes irregularities on t h e diffusion current. T h e formation of the precipitate a t the electrode and its effects were studied by the aid of niicroscope and i - t (current-time) curves. In the second reduction step the C-Hg bond is split t o form free mercury a i d an aromatic hydrocarbon. New Polarometric Titrations in Pharmaceutical Analysis.
K.LI,VOD.\ \ N D ,r,
R.
ZGK.~.
Polarometric titrations may be profitably used in pharmaceutica I analysih. Little work has been done along thib line, arid the following estimations contribute to such applications of polaroniet,ric titration*. Estimation of antipyrine by precipitation titration with a solution of mercuric perchlorate, used iii drug mixtures. Eatimation of 3,5-dioxo-1 ,2-diphe1iyl-4r~-but~~Ipyrazolidiiie (used ad a modern analgetic and antirheumatic under the name Irgapyrin) in injections in presence of amidopyrine with mercuric perchlorate. Estimation of different salicylates in drug mixture8 with the 3anie agent. Estimation of tartaric acid :ind tartrates by precipitation with lead salts. imation of glycerophosphntes by precipitation with lead >a1t a . imation of zinc in fodders, eye aashea, :tiid drop3 by titration with potassium ferricyanide. Determination of Carbon Disulfide in the Atmosphere.
J. H E Y -
ROVSKY.
Carbon disulfide has been found to give well defined polarographic waves in practically all electrolyteb. For the analysis of air a 10% solution of sodium sulfite is recommended, as it absorbs oxygen and shows only the two wavea due to carbon disulfide. T h e first of these occurs a t the applied voltage of 1.0 volt and t h e second, which is somewhat smaller, appears a t 1.4 volts, coinciding with t h a t of formaldehyde. Air is slowly yassed through the sulfite solution placed in a special 1-ml. microvessel, being sucked by a small turbine. T h e quantity of 1 microgram of carboii disulfide in 1 ml. is distinctly shown. With the same sensitivity the depolarization effect of carbon disulfide is also shown oscillographically. These, as well a* t h e polarographic effects, are different from those of hydrogen sulfide.
ANALYTICAL CHEMISTRY Polarographic Determination of Cyclopentanone and Cyclohexanone. M. B ~ E Z I K A . T h e author investigated polarographically the reaction taking place between cyclopentanone, cyclohexanone, and methylcyclohexanone, with ammonium hydroxide, glycine, alanine, methylamine, or ethylamine, v e r s e d the scheme of a two-electron reduction of the ionized ketimine, and discussed t h e influence of structure of ketones and amines used upon the reaction equilibria. -4cyclanone in concentrations down t o 10 - 6 M can best be determined in the methylamine buffer solution-1 A' methylamine and 1 N methylamine hydrochloride. Occasional maxima appearing on polarographic curves of ketimine are easily suppressed by a small addition of gelatin (about 0.005%). The concentration of the buffer solution must be kept constant during t h e analysis. It is necessary to bear in mind t h a t t h e polarographic waves of t h e imino compounds of other ketones or aldehydes can interfere with the polarographic waves of cyclanones. Polarography of the Derivatives of Barbituric Acid. P. ZUMAN.
Colchicine iq flowers of colchicum is determined polarographically according to Santavf. A sample of dried drug is extracted by methanol in a Soxhlet apparatus. Methanol is then evaporated in vacuo, the rest is dissolved, and the interfering substances are precipitated by basic lead acetate. The excess of lead is then removed by the solution of sodium phosphate and t h e filtrate is examined polarographically in the McIlvaine buffer solution of p H 7 . 6 . Polarographic Investigation of Insecticides.
Barbituric acid and a number of its derivatives-except t.hose t h a t are substituted on a nitrogen atom-show one or more anodic waves due t o formation of compounds with mercury which are adsorbed a t t h e electrode surface. T h e half-wave potentials depend on the pH. Their values in t h e borate buffer of p H = 9.2 are about -0.1 volt 2i8. N.C.E. The wave heights are in a certain range proportional t o t h e concentration, but above a definite concentration they are constant. More positive waves appear most,ly a t concentrations a t which t h e main wave has reached its constant height. The limiting concentration for barbituric acid is about 5 X 10-6 M, and for veronal 1.2 X 10 M . T h e limiting concentration is greater a t shorter drop times. Therefore the use of the streaming mercury electrode makes possible the determination in a wide concentration range. I n this case the electrolytic cell must be equipped with a separate unpolarizable electrode of 2% cadmium amalgam in t h e saturated solution of cadmium sulfate. T h e large condenser current, of an order of 10-6 ampere per volt, must be compensated.
-'
D . DOSKOEILOVL.
lldditire compounds of halogens-iodine chloride, iodine bromide, and bromine-with ethylene, hexene, and styrene were examined by the polarographic method in methanolic solutions. All these compounds show extended irreversible waves. Best defined (steepest) waves appear when iodine bromide is used, but styreneiodine bromide is not suitable for the analytical determination because of its rapid decomposition in methanol. The determinat,ion of styrene in t h e presence of hexene is based on brominated products; the halfwave potential in 90% methanol of t h e former is -0.05 volt, of the latter is -1.6 volts. Three mole per cent of styrene can be determined in the presence of 97 mole 7 0 of hexene, or of another direct-chain mono-olefin, with the usual polarographic accuracy. Polarography in Production and Research on Antibiotics. DOSKOEIL AND M. URX.
J.
Polarographic methods are applied both for checking of the fermentation process, and for analysis of concentrates, intermediates, and finished products of different antibiotics. Polarographic determination of the rate of oxygen consumption of living mycelium was successfully applied. Among the antibiotics, streptomycin and Chloroniycetin can be determined directly. Polarographic behavior of these substances a s well as of aureomycetin was described. The author also presented a new method for determination of penicillin G, based on nitration of this substance and polarographic determination of the resulting nitro compound. Polarography of Aldehydic Heart Glycosides.
Polarographic Determination of Colchicine in Flowers of Colchicum.
J. B U C H N I ~ E K .
J. KORYTA
AXD
Polarographic Determination of Mono-olefins.
k-strophanthoside, and convallotoxine were studied. T h e aglycone of these glycosides, strophanthidine, behaves similarly. Unlike these substances, t h e glycosides g-strophanthine and gitoxine, which have no aldehydic group, do not show any of the described effects. It is therefore possible to distinguish the heart glycosides with the aldehydic group from the other heart glycosides. The content of aldehydic glycosides in isolated technical products can be determined polarographically in glycine buffers.
P. 2uhf.m
ASD
F. S A S T A ~ . Heart glycosides with an aldehyde group a t G o of the steroid skeleton show depolarization effects of two kinds. I n the buffer solutions adsorption waves were observed, the height of which does not change with t h e glycoside concentration. The adsorption character of these waves follows from the dependence on the height of mercury column and from the depression of the condenser current. B y using t h e streaming mercury electrode thelimit of concentration is increased and the wave is suitable for q u a n t i t a t i w determination. I n the glycine solution which had been titrated to one half by sodium hydroxide, polarographic waves were observed which belong to the reduction of the aldimine condensation products. These naves depend on the concentration of glycine a s it has been observed on numerous aldehydes, ketones, and ketoacids. .Imong aldehydic heart glycosides. cymarine, k-strophanthidine,
J.
~ ~ D ~ M AEN K D
I. SMOLEA. During the investigation of the a-,,3-, and y- isomers of benzene hexachloride (BHC) and of the p , p ' - and o,p'-isomers of dichlorodiphenyltrichloroethane (DDT) it was found t h a t with decreasing concentration of ethanol the height of the wave also decreases and i t s half-wave potential is shifted t o more positive values. .The wave of the D D T is deformed in the solution of lithium chloride, but attains a regular character in the presence of gelatin or in solutions of tetraalkylammonium salts. The authors suggest an analytical method for polarographic determination of gammexane in technical B H C (a modification of the method of Nakarima and others) and of D D T , based on the different rates of decomposition of the p , p ' - and o , p isomers in alkaline solution.
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Polarographic Determination of Oxidation Products of Codeine. V. F O ' ~ T O AND V ~J. VOLKE. These compounds are reduced in one or two waves, if they contain an oxygen bridge next to the free carbonyl group. For the determination of dihydrocodeinone and dihydro-oxycodeinone their first twoelectron and diffusion-controlled wave was used. h s a supporting electrolyte t h e alkaline borate buffer solution or lithium hydroxide was used. Acetyldimethyldihydrothebaine,which is not reducible polarographically, was determined as dihydrocodeinone after hydrolysis in the lithium hydroxide solution. I n the presence of acetyldimethyldihydrothebaine the dihydrocodeinone was determined in an acetate buffer solution where the acetylated group is stable. T h e half-wave potential of the first wave of codeinone is more positive than t h a t of its dihydro derivatives. Polarographic Determination of Heroin and Dilaudid. V. F o i l ~ o v i .
J. VOLKH)
AND
Polarographic determination of 3,6-diacetylmorphine (heroin) is possible after hydrolysis in the solution of hydrochloric acid and nitrosation by the solution of potassium nitrite. Potassium hydroxide is used a s a supporting electrolyte. Dilaudid (dihydromorphine) gives one or two reduction waves which depend on the p H of the solution. The first wave is suitable for t h e determination of dilaudid, preferably in 0.1 N lithium hydroxide or in Sijrensen's borate of p H 11 or 12.38. I n strongly alkaline solution t h e wave of dihydromorphinone can be distinguished from those of dihydrocodeinone and dihydro-oxycodeinone. Indirect Polarographic Determination of Acrylonitrile. B. &I.&TYSKA I. K ~ S S L E R .
AXD
Acrylonitrile gives in the potential range from 0 to 2.4 volts no polarographic wave, but can be determined indirectly on t h e ground of its rapid irreversible reaction with primary mercaptans. T h e method of Beesing and Tyler based on the determination of excess mercaptan offers no reliable results, because the mercaptan solution is unstable. To avoid this disadvantage the authors mixed the m e r c a p t a n solution with a solution of silver nitrate and determined the excess of silver polarographically. If a sample of acrylonitrile is added before the addition of t h e silver nitrate solution, a n increase of the wave of silver is found which is proportional t o the concentration of acrylonitrile. BIOCHE,MISTRY A 3 D MEDICINE
Polarographic Determination of Vitamin BI in Pharmaceuticals.
R . PLETICHA. T h e red precipitate which is formed by the complex anion BiI4- with ritamin B I is dissolved in a 10% Seignett salt solution where the iodide
V O L U M E 2 4 , NO. 5, M A Y 1 9 5 2
917
ion gives an anodic wave, t h e height of which is proportional to t h e amount of vitamin B1. Determination of Cadmium in Biological Materials.
D. BuCH.4-
L0V.L.
Samples of blood or urine are mineralized by a mixture of nitric and sulfuric acids. T h e solution is then neutralized by a buffer solution of p H 9 t o 9.5, and cadmium and several other metals are extracted by the chloroform solution of dithizone. After conversion of t h e dithizonates t o chlorides, t h e solution of chlorides in 0.1 N potassium chloride and 0.1 N hydrochloric acid is examined polarographically. By tliia method i t is possible to determine 0.5 microgram of cadmium. Determination of Hydroquinone in Urine. 9. SKRAMOVSK~.
V. B E R G E R O V AN ~D
Forty milliliters of urine is hydrolyzed by boiling with 0.3 ml. of sulfuric acid. After neutralization by calcium carbonate, hydroquinone is extracted by ether and then oxidized by a 0.1 N solution of ceric sulfate to quinone, which is distilled into a n acetate buffer solution. This solution is then examined polarographically. Standardization of the Filtrate Test.
R. B R D I ~ K . ~ .
For the polarographic investigation of blood serum the following procedure isused. At room temperature 0.4 ml. of blood serum (taken when t h e stomach is empty) is mixed with 1 ml. of 0.1 A- potassium hydroxide and left t o stand 45 minutes. Then the solution is mixed with 1 ml. of 20y0 sulfosalicylic acid and t h e precipitated proteins are separated from the solution by a hard filter (best is Schleicher and dchtill, No. 575, 7 ern ). Then 0.4 ml. of the clear filtrate is added to 4 ml. of the cobaltic solution, which is Jf in Co(”a)sCla, 0.1 Ain ammonium chloride, and 1 iV in ammonia. A small beaker with the mercury pool anode is used as a n electrolytic cell. T h e polarograms are recorded from the applied voltage of 0.8 volt with such a galvanometer sensitivity t h a t the height of t h e wave of cobalt in t h e pure cobaltic solution is about 20 mm. T h e results can be compared only when using the same capillary and working a t t h e constant level of mercury. Best are capillaries of a n internal diameter of 0.05 t o 0.U7 mm. and drop time of about 2 seconds. T h e normal limit of t h e filtrate test must be determined for the polarographic equipment as a mean of a t least 30 clinically healthy persons. With pathological sera t h e height of t h e protein double wave marks the progress of pathological processes. Electrophoretic and Polarographic Investigation of Serum Proteins. J . HOMOLKA. Simple equipment for electrophoresis on filter paper was described. T h e dried paper is divided into transverse portions from which the proteins are dissolved by 0.9% sodium chloride. T o each portion t h e polarographic cobaltic solution is added and t h e polarograms are recorded from 1.5 t o 1.7 volts by using as anode a silver wire, wound around t h e capillary. From t h e heights of t h e waves a t 1.6 volts the electrophoretic distribution of proteins active in t h e BrdiEka test can be calculated in t h e usual manner. T h e provisional average of clinically normal sera is given. From this combined method of protein research new progress in the elucidation of the BrdiEka test is expected. Application of the Polarographic Method for the Study of MetaboAND A. VAVRUCHOVA. lism of Pediococci. A. KOCKOVA Diacetyl and acetoin, which are products of metabolism of the brew sarcine (Pediococcus), can be determined polarographically in very small concentrations. Polarographic Determination of Ascorbic Acid and Sulfhydryl Compounds in Fruits. P. Z n 1 . m . T h e content of ascorbic acid and sulfhydryl compounds in tomatoea was investigated by t h e polarographic method with respect t o t h e genetic factors, storage, and degree of ripeness. T h e change of content of ascorbic acid and of sulfhydryl compounds during the canning oi tomatoes was determined, and it.was found t h a t t h e sulfhydryl compounds have a protective activity for ascorbic acid, being more e a d y oxidized. An attempt was made to isolate sulfhydryl compounds from t h e juice of t h e fruits of t h e elder tree (Sambucus nigra L.). Polarographic Behavior of Anthocyaens.
acidification with dilute sulfuric acid t o p H 1.6 t o 3. it i- possible t o determine anthocyanins in fruit juices and, after extraction with 1% hydrochloric acid, also in dried flowers.
P. ZGMAN.
T h e anthocyanins are reducible a t the dropping mercury electrode. From the p H dependence of the waves of anthocyanin solutions in water and ethanol it follows t h a t a formation of a new wave corresponds to every change of the color of the solution. A probable scheme for the hydrolysis of anthocyanins was suggested. I n the solutions obtained from plant tissues a similar dependence on t h e p H was observed and so the identity of these waves was proved. =ifter
Polarographic Determination of Tocopherols in Plant Oils. KNOBLOCH.
E.
T h e tocopherols in the unsaponifiable, desteroliaed residue of plant oils are converted to the corresponding quinones. which give in a n acetate buffer solution containing 75% ethanol well defined reversible polarographic waves. It is possible to determine the sum of tocopherols and also the cy-, @-, and y-tocopherols on the basis of the different oxidation-reduction potentials of t h e quinones. Individual tocopherols were isolated from different oils by combining saponification, molecular distillation, and chromatography and were identified by their infrared spectra. Polarographic Determination of Penicillin in Samples.
E. K R E J ~ .
On the polarographic curves of penicillin G in the buffer solution of p H 4.5 two waves were observed, t h e heights of which have the ratio of 1 to 2. T h e height of t h e waves depends on the time during which the penicillin was dissolved in the buffer. A t t h e beginning, both t h e waves increase from zero to a maximum, then they decrease slowly until they completely disappear. These waves probably belong t o the electroreduction of t h e penicillic acid formed from penicillin. The height of the wave is under the same conditions proportional t o the original concentration of penicillin. On this the polarographic determination of penicillin is based. On a polarogram the time dependence of the first wave is registered, a t a constant potential, t o record t h e maximum of the curve. T h e value of current in the maximum, after subtraction of the charging current, is compared w i t h the current of a standard obtained a t under the same conditions. Determination of Benzene and Toluene in Air and in Biological Materials. J . S R B O V ~ . T h e determination is based on two procedures: T h e sum of both hydrocarbons is determined after nitration. Toluene is removed by bubbling the air through 90% sulfuric acid or through the chri~niosulfuric mixture. Determination of Formaldehyde in Air.
M. P A P I ’ T ~ ~ E K .
Air is bubbled through the solution of hydroquinone in calcium hydroxide, where a condensat,ion product is formed which gives a wave 200 mv. more positive t h a n t h a t of formaldehyde. Oxygen is removed by hydroquinone. Polarographic Determination of Oxygen in Blood.
J. ROELGEK.
T h e author applied SimLnZ’s method for the determination of oxygen in blood (Proceedings of First Polarographic Congrer-. Prague, 1961, p. 781) in \-arious cases of thorax surgery. Determination of Sterols.
31. I,EDTIXA.
Yarious sterols and steroid con~poundscan be determined polarographically after nitration, and give well measurable waves which are suitable for quantitative determination.
POLAROGRAPHIC APPARATUS Survey of Usual Types of Polarographs and Experiences with Them. J. M A ~ E K . Automatic Compensation of the Influence of the Potential Drop Caused by a Small Conductance of the Solution. D. IIKOYIC. Methods for Measuring Limiting Currents.
A. V ~ & E P .
Properties of the Mirror Galvanometer with Respect to Its Application to Polarography. V. HAJKO. T h e author presumes t h a t through the galvanometer coil flows a current which changes periodically with time and t h a t the galvanometer is critically damped. The morement of the coil is in accordance with a certain differential equation, the solution of which shows t h a t the mean value of the galvanometer deflection is proportional to the mean current. Precision Automatic Pipet.
3. J-. 1.NOYAK
Polarographic “Vessel with Reference Electrode Separated by Cellophane. L. SERAK. The resistance of t h e membrane is 7-ei-y small and satisfies the conditions for the work in aqueous wlutioii, i l l the ab>ence of substances attacking rubber or cellophane.
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