Excess Of Permanganate Research Articles

Colorimetric determination of traces of selenium, tellurium, manganese and cerium

Methods are described for the colorimetric determination of micro- and semi-micro quantities of selenium, tellurium, cerium and manganese. The test solution in 0.35–3 M condensed phosphoric acid medium is oxidized with an excess of permanganate. The colour intensity of the unreacted permanganate is measured at 530 nm.

Analysis of tellurides of lead and tin by automatic titrations

An analytical method based on automatic potentiometric EDTA and redox titrations was developed for the analysis of tellurides of lead and tin.First, the sum of lead and tin is titrated at pH 4.5 by adding a known excess of EDTA and back-titrating with a standard lead solution. After addition of ammonium fluoride to mask the tin, the EDTA released from the Sn-EDTA complex is titrated with standard lead solution. Alternatively, after the determination of total lead and tin, lead may be determined by back-titration with standard lead on a separate sample aliquot using tartaric acid to mask the tin. Tellurium is separated as tellurous acid, which is then dissolved in a dilute sulfuric acid solution and oxidized by permanganate at room temperature; the excess permanganate is back-titrated with iron(II) solution automatically. This titration may also be used to determine tellurium in the presence of lead and tin after treatment with perchloric acid. Accuracies of 0.1-0.2% can be obtained.

Determination of citric acid in urine and in serum.

A method is described for the determination of citric acid in the routine clinical investigation of urine and serum. It is based on a combination of the methods of GEY, LANE and CHEN. The method has been used for several years and has been completed by a statistical analysis. Es wird die Beschreibung einer Zitronensaurebestimmungsmethode im Harn und Serum, die sich gut zu Reihenuntersuchungen in der Klinik eignet, gegeben. Sie beruht auf der Kombination der Methoden vonGEY und LANE und CHEN. Wahrend mehrerer Jahre wurde diese Methode angewendet und durch eine Statistik erganzt. Recent progress in clinical chemical methods has shown the importance of citric acid in the different metabolic pathways. Its storage and release is influenced by vitamin D and parathormone, and it is a metabolite of the Krebs cycle. Citric acid is also a bone component. Moreover, the secretion and tubular reabsorption of renal citric acid are two problems which remain unsolved. Determinations of serum and urinary citric acid are thus not only of interest in the different bone diseases, but also in certain kidney and liver diseases. The clinical laboratory therefore needs a method for the determination of citric acid in urine and in serum, which is precise, rapid and not too complicated. This paper describes such a method which we have used in our laboratory. Our six years of experience have shown it to be capable of fulfilling all the necessary requirements of the clinical laboratory. Above all, we would like to emphasize its accuracy which permits, for example, the differentiation of certain diseases by analysis of the citric acid levels in serum. We have found many methods for the determination of citric acid in the literature, most of them based on the conversion of citric acid into pentabromacetone (Pba), with various modifications for its oxidation and extraction (2—12). We have retained the methods of GEY, and LANE and CHEN. After trying both, we decided that a judicious combination of the two would permit us to shorten the time required for the determination without sacrificing its sensitivity. We therefore kept LANE et aFs sequence of oxidation at low temperature and the subsequent reduction of the excess permanganate by hydrogen peroxide. We then substituted GEY'S technique for extraction with petroleum ether, elimination of traces of acid, and formation of the Pba-thiourea-borax complex. Thus the combination of the two methods permits us to shorten the time required for the determination without affecting the accuracy of the results. By adopting GEY'S method of extraction, we have eliminated certain inherent errors of the Nal-ethanol extraction, for example the influence of light, temperature and the possible contamination of theNal-Pba-ethanol mixture by acids, which would have to be eliminated by washing with water and the phosphate buffer. Furthermore, the Pba-thioureaborax complex is not affected by the presence of s-hydroxybutyric acid, acetone and succinic acid, even in pathological quantities. The Pba-Nal-ethanol reaction is sensitive to the aforementioned compounds, as well as to aspartic acid.

An absorptiometric method for the determination of traces of copper in biological materials with dithizone

A very sensitive method is described for the determination of traces of copper in biological materials. The sample is wet ashed with a mixture of sulphuric, nitric and perchloric acids and brought into solution with citrate and ammonia. Copper is separated from iron, zinc and other metals by extracting it from this solution at a pH of about 4.5 with successive portions of a solution of dithizone in carbon tetrachloride. It is then transferred to an aqueous phase by shaking with a solution of potassium permanganate from which it is re-extracted with dithizone at a pH of about 1.5 and determined absorptiometrically. The final extraction is carried out in the presence of sulphurous acid to reduce the excess permanganate, and iodide to prevent interference from mercury, silver and bismuth. The absorptiometric procedure used avoids the difficulties encountered in other procedures which arise from the instability of dithizone in solution, and it automatically corrects for the amount of copper in the blank. This method can be used to determine 1 μg of copper or less with a satisfactory degree of precision and is therefore particularly useful for studies of copper deficiency and for analysing small samples.

Oxidation of sulphides with alkaline potassium permanganate

Sulphides are oxidised with potassium permanganate in alkaline medium to give dithionate. A method based upon this reaction is proposed for the determination of sulphides. The method consists in mixing the sulphide solution with an excess of permanganate in presence 1–2 M NaOH and 0.2 g telluric acid. The excess permanganate is then treated with ferrous ammonium sulphate in acid medium and the excess ferrous titrated with permanganate.

Oxidations with alkaline permanganate using monovalent thallium for the back titration: Estimation of hydrazine

Oxidation of liydrazine in alkaline solutions with KmnO 4, gives inaccurate results both in the presence of absence of telluric acid. The titration curve is characterized by two inflections. Titration of KmnO 4 with hydrazine gives good results in the presence of Ba +2 ions and 0.75–1 NNaOH (when MnO 4 - gives MnO 2 -) or in the presence of 0.5–2.5 N NaOH only (when MnO 4 gives MnO 2). Hydrazine could be estimated by oxidation with KMn0 4 either in the presence of Ba +2 ions or telluric acid, after which the excess permanganate is back titrated with monovalent thallium. The alkalinity is Kept at 1 N NaOH.

A SPECTROPHOTOMETRIC METHOD FOR MEASURING THE BREAKDOWN OF HYDROGEN PEROXIDE BY CATALASE

Several methods have been developed for following the breakdown of hydrogen peroxide catalyzed by catalase, but these either have not been sufficiently quantitative or have not proved rapid enough to yield reliable data during the critical 1st or 2nd minute of the reaction. Chemical procedures in which residual peroxide is titrated with permanganate (l-3) or an excess of permanganate is measured calorimetrically (4) are accurate except for reaction times of less than a minute, although Lemberg and Foulkes (5) developed a micromethod for obtaining data every 10 seconds (see also Ogura et al. (6)). Considerable variability is unavoidable, however, when samples must-be taken at such short intervals. The manometric method for measuring oxygen evolved from the system proved in detailed studies to be unsuited for following the rapid breakdown of peroxide in which a diffusion process across the liquid-air interface becomes limiting. This is manifested by changes in both the order of the reaction and the rate of evolution of oxygen with variations in the rate of agitation of the reaction mixture (7). Direct measurement of hydrogen peroxide by polarography provides good quantitative data during the 1st minute of the reaction which fit first order kinetics (8). However, an elaborate, special, electronic circuit is needed for such measurements. Furthermore, as pointed out by Bonmschen, Chance, and Theorell (8), this method appears to give lower values for catalase activity than do titration techniques. Preliminary experiments for following the breakdown of hydrogen peroxide by observing the decrease in light absorption of peroxide solutions in the ultraviolet were reported by Chance (9) and Chance and Herbert (10). The potentialities of this method have been investigated and a quantitative, spectrophotometric technique for following the breakdown of hydrogen peroxide has been developed for routine studies of catalase kinetics.

A Rapid Micro Method for Determining Diodrast and Inorganic Iodide Iodine in Blood and Urine.

The present paper describes a rapid micro method for the determination of diodrast or inorganic iodide iodine in whole blood, blood cells, plasma or urine. Hundreds of determinations of diodrast and inorganic iodide added to water, to urine and to filtrates have shown substantially a 100% recovery. With the method in its present form not all of the iodine is recovered from some other iodine compounds investigated, skiodan, iodeikon and isoiodeikon. The method has not been applied to normal blood or urine. The diodrast and skiodan used in this work were kindly furnished by the Winthrop Chemical Company; the iodeiokon and isoiodeikon by the Mallinckrodt Chemical Company.Principles of Method. The iodine-containing sample is digested in an acid solution of potassium permanganate, the iodine thereby being oxidized to iodate and the organic matter destroyed. The excess permanganate is reduced by addition of nitrite and the excess nitrite then destroyed by urea. The iodate is then titrated against a standard 0.0...

Societies and Academies

LONDON. Society of Public Analysts, Nov. 5.—G. M. Moir: The determination of the milk proteins. By mixing definite quantities of milk with a suitable acetic acid and sodium acetate buffer, maximum casein values are obtained between pH 4-5 and 4-7. Casein thus precipitated is identical with the substance precipitated by acetic acid alone at pH 4-2. For the combined determination of albumin and globulin the nitrate obtained from the iso-electric precipitation of the casein is treated with trichloroacetic acid to give a concentration of about 4 per cent, and the nitrogen in the resulting precipitate determined by Kjeldahl’s method. Casein and globulin are determined by precipitation with neutral saturated magnesium sulphate or sodium sulphate, and the individual proteins calculated by difference.—S. G. Clarke: The lead reduction method for the volumetric determination of tin, and the interference of copper and antimony. Tin is determined by Powell’s method of reduction from the stannic condition by means of lead, and direct titration with iodine, in an atmosphere of carbon dioxide. Copper causes the results for tin to be too low in direct proportion to the amount of copper present. Antimony also interferes, a considerable amount of tin being removed from the solution by the precipitation of the antimony; this reacts with the iodine during the titration.—W. J. Agnew: A new method for determining traces of chromium in steel. Chromium is oxidised with potassium permanganate, excess permanganate being reduced by hydrochloric acid. The iron is then precipitated with sodium carbonate, and the dichromate determined by Evans’s colorimetric method based on the purple coloration which it gives with diphenylcarbazide.

Gasometric Determination of Blood Calcium.

The calcium is precipitated and washed in a centrifuge tube as in the Kramer-Tisdall method, and is redissolved in 2 cc. of 1 N sulfuric acid. The solution is transferred to the manometric blood-gas apparatus of Van Slyke and Neill, using sufficient water for washing to bring the volume up to 6 cc. Dissolved air and CO2 are removed by shaking the solution 2 minutes in the evacuated chamber and ejecting the extracted gases. One cc. of 0.1 N potassium permanganate, previously acidified with 1/20 volume of 0.1 N sulfuric acid, to decompose any carbonate present as contamination, is added. The excess permanganate oxidizes the oxalic acid to CO2. The chamber is evacuated and shaken 3 minutes. The gas pressure P1 is read on the manometer with the gas volume at 0.5 cc. if the calcium is being determined in a 1 cc. serum sample, at 2 cc. volume if a 3 cc. sample has been used. After reading p1 the CO2 is absorbed with 1 cc. of 5 N sodium hydroxide, and p2 is read with the same gas volume in the chamber. The pressure due to the CO2 from the oxalate is p1-p2-c, where c is the value of p1-p2 determined in a control analysis of the reagents. The CO2 in millimols is estimated from Table III of Van Slyke and Neill. If a 1 cc. sample of serum is used, the factor in the column for “Sample = 2 cc., s = 7.0, a = 2.0, i = 1.014” is multiplied by 2 × 1.03/1.014 × 2.0/0.5 = 0.508, to obtain the factor giving milliequivalents of Ca per liter; since in the present analysis the sample is 1/2 as much, i is changed to 1.03, and a is changed from 2.0 to 0.5, only s being the same as on the table.