Isotope dilution mass-spectrometry can be applied to the determination of minute amounts of potassium in distilled water, deionized water and snow melts from snow strata in Greenland and Antarctica. Sample size required is 10 g. The ion source used for this purpose is characterized by a specially designed single-filament unit, which is heated with accurately controlled. electric current, and makes it possible to emit an intensive mass spectra from 10^-15 g of potassium.
0.07 μg of ⁴¹ K spike in 0.1 g of 5 per cent nitric acid is accurately weighed in a 50 ml teflon beaker. 10 g of snow melt is poured directly into the beaker from the agitated sample bottle and weighed. The mixture is evaporated to 50 μl in a heated steel tank which has high purity nitrogen gas streaming through it. The small drop of concentrated liquid is transfered onto the tantalum filament by means of a quartz micropipette.
The analytical decision of mass spectrometry is 1 per cent in a relative error and is not bitterly affected by the presence of foreign substances. Relative errors resulting from isotope effects are minimized. to the degree of 0.3 per cent by running the mass spectrometer under common conditions, especially at the definite intensity of filament current for ionizing potassium. Snow melts usually contain minute amounts of silicate dusts, so there is concern as to whether the potassium in the dusts equilibrates with the element in the spike. If it does not, the results will tend to be low, since the potassium isotopes in a salt matrix will be driven off from heated filament more easily than those bound up in a silicate matrix. No severe changes are observed among isotopic abundances with increase in filament current. Equilibration may exist between both kinds of potassium. Being judged from silicon and titanium amounts, the potassium from silicate dusts bears only 10 per cent of total potassium while the element from sea salts is predominant in the remainder.
Potassium concentrations are found to be at levels of 0.18 ppb in redistilled water, 0.19 ppb in deionized water, 1 ppb in antarctic snows and 3 ppb in Greenland snows.
In Greenland snow strata, potassium shows its enrichment in spring layers as dusty components do. In both polar regions, any appreciable variations of potassium concentration have not been detected in whole year composite samples since 1750.

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For the study of a hydrodynamic electrode, an apparatus with a working electrode of a running gold wire loop was constructed, and the basic characteristics of this system were discussed in the case of the automatic stripping analysis of lead ion.
In this apparatus, the running wire electrode passes through the cleaning electrolytic cell, the electrode-position cell, and the electrodissolution cell in turn. Each of the deposition and the dissolution cells is divided by a sheet of cation-exchange membrane into the room of the running wire electrode and the room of an Ag-AgI counter electrode, which serves as the reference electrode. The standard electrolyte solution {1 × 10^-3 or 1 × 10^-4 M Pb(NO₃)₂, 0.1 M KNO₃, pH 4 with HNO₃} is fed to the deposition cell and an electrolyte solution (0.1 M KNO₃, pH 4 with HNO₃) is also fed to the dissolution cell from a constant head, but the electrolyte solutions in the rooms of the counter electrodes (1 M KI) are circulated with the respective tube pump.
The cleaning electrolytic cell is separated into three chambers along the wire electrode, and each of the chambers contains a platinum counter electrode. The counter electrode in the central chamber is connected to the positive terminal of a constant current source, and the other two are connected to the negative terminal. The gold wire working electrode is thus cleaned electrolytically on passing through the three chambers.
The main feature of this apparatus is that the solid electrode with pretreated surface is automatically passed through the deposition and the dissolution cells filled with electrolyte solutions. In this system the renewal of the surface of the working electrode causes no increase in the charging current because the capacitance of the electric double layer does not change. Since the most promising analytical application of this system is that to the stripping method, an automatic stripping analysis of lead ion was studied in detail.
Although the deposition current due to the reduction of lead ion flowing through the deposition cell was not observed clearly because hydrogen was evolved by the cathodic polarization of the running electrode, the anodic dissolution current through the dissolution cell was determined clearly enough. The recoveries of the electrode position were 1.9% for 1 × 10^-3 M and 5.4% for 1 × 10^-4 M lead ion when the flow rate of the sample solution was 27 ml/min and the running speed of the wire electrode was 20 mm/min. On the other hand, the ratio of the dissolution current to the deposition current remained fairly constant.
In order to increase the repoducibility it is necessary to make the stream of the electrolyte solutions uniform in the deposition and dissolution cells and to increase the running speed of the electrode.

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The present paper describes the microdetermination of halogens in organic substances by the argentimetric titration after the Schoniger combustion. The titration with silver nitrate solution was carried out in an aqueous acetone medium using dithizone as indicator. The content of water in the acetone solution should not exceed 3% for chlorine, 12% for bromine, and 50% iodine, because in the presence of an excess of water silver nitrate reacts with dithizone before the formation of silver halides. The presence of chloride ion does not interfere the iodide titration. When water content is adjusted adequately, simultaneous determination of chlorine and iodine can be successfully performed.
The end point is apt to be confused with the color change due to the decomposition of dithizone when no stabilizing agent is present. It was shown that phenylcarbazyl derivatives are efficient to prevent the decomposition of dithizone. Successful results were obtained by using 0.01% dithizone and 0.05% diphenycarbazide as indicator.
Nitrite formed by the combustion of nitrogen containing organic substances quickly decomposes dithizone in the titrating solution. Hydrazine is perferable for decomposing the nitrite to urea and ammonia; it dedecomposes the nitrite in one minute at 50°C, or in 5 minutes at the room temperature.
Sulfur, phosphorus, and fluorine do not interfere the titration, but mercury, arsenic, and selenium interfere.
The recommended procedure is as follows. In a Schoniger flask, a mixture of 1 ml of distilled water, 2 drops of 5% hydrogen peroxide, and 2 drops of 1 N lithium hydroxide are placed. After the flask is filled with oxygen, 35 mg of sample folded in a piece of filter paper is ignited. Then the spreading part of the inlet of the flask is filled with a washing liquid (a few milliliters of acetone for chlorine, 5 ml of water for bromine, 10 ml of water for iodine), and the stopper is removed. After the addition of a drop of hydrazine hydrate solution (1:1) and 0.2 ml of 50% sulfric acid, the mixture is allowed to stand for more than 5 minutes. After rinsing the stopper throughly with 50 ml of acetone, 1 ml of the dithizone indicator solution is added. The solution is then titrated with the standard 0.005 N silver nitrate-isopropyl alcohol solution until an yellow color appears, and after the addition of further 3 ml of the indicator, the titration is continued until a clear orange-yellow color appears. Correction is made for the blank. Accuracy of the determination is within ±0.3%, and 56 runs can be performed in an hour.

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Several dye methods which are based on the formation of colored compounds with acid dyes, have been proposed for the determination of amines or quarternary ammonium salts. Although the sensitivity of the dye methods is quite sufficient for many purposes, situations often occur in biochemical field where a more sensitive method is necessary. Since fluorometry is known to be 10 to 100 times more sensitive than colorimetry, a fluorescent tetrabromosulfonfluorescein (TBSF) was used as the acid dye for the determination of long-chain secondary or tertiary amines, such as amitriptyline, nortriptyline, chlorpromazine, carbetapentane and tripelenamine.
Fluorescent TBSF was synthesized by bromination of sulfonfluorescein. A TBSF standard solution (2 μg/ ml) and a TBSF solution (200 μg/ml) were prepared by dissolving the reagent in methanol and in water, respectively. An alkaline methanol was prepared by diluting 1 ml of 0.5 N NaOH to 100 ml with methanol. Chloroform was used as the extracting solvent.
Determination of amitriptyline: To a 2 ml portion of amitriptyline hydrochloride (0.55.0 μg/ml in 0.1 N HCl), 1 ml of the TBSF solution and 3 ml of chloroform are added. The mixture is thoroughly stirred for 1 min by a mixer. After standing for a few minutes in order to separate the two phases, the upper aqueous phase is removed, and exactly 2 ml of the chloroform phase is transferred to another test tube containing 2 ml of the alkaline methanol. After mixing the two phases, the fluorescence intensity is measured with excitation maximum at 535 nm and with emission maximum at 550 nm. The fluorophotometer is calibrated by the TBSF standard solution. A linear relationship between the fluorescence intensity and the concentration of amitriptyline was obtained (1.6 16.0×10^-9moles/ml).
Fig. 1 shows that the optimum pH for the solvent extraction is 2.5, and Fig. 2 shows that the maximum relative fluorescence intensity is obtained by use of 0.02% TBSF solution. As shown in Fig. 3, the fluorescence intensity is very stable.
The interference with various compounds in blood and urine was examined. Most of them caused no effect on the results. As expected, the proposed method is about 100 times more sensitive than the usual colorimetric method using acid dyes. This method could be applied to the determination of basic drugs in blood, urine or pharmaceutical preparations. For example, amitriptyline could be extracted from alkaline urine with n-hexane, back-extracted into 0.1 N HCl and then an appropriate portion of it was measured by the above determination procedure.

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A sensitive and accurate method has been developed for the determination of trace amounts of manganese and applicated to high-purity silicon, hydrofluoric acid and nitric acid. The method is based on the catalytic action of manganese on the oxidation of Malachite Green (MG) by periodate. Under the conditions, 4.32 × 10^-6 M MG, 4.25 × 10^-4 M potassium periodate, pH 3.8 buffered by acetate, ionic strength 0.1, and 31°C, a linear relationship was obtained between the initial concentration of manganese up to 100 ng and the observed first order rate constant k which was evaluated from the logarithmic plot of the absorbance at 615 nm against the reaction time t.
Using this relationship, manganese as low as 5 ng/ 20 ml could be determined by measurements of the reaction rate.
Various factors affecting the reaction rate have been studied in detail.
As the pH increased, the reaction rate also increased but the reproducibility was not so satisfactory, and a deviation from the first order reaction was observed above pH 4.9.
The ionic strength extremely affected the reaction rate, namely, the rate constant k decreased with an increase in the ionic strength.
An apparent change in the temperature dependence of the reaction rate was observed at about 29°C; the dependence on the temperature became only slight above this temperature as compared with that below it.
Making the experiments above 30°C and at low ionic strength is advantageous in order to obtain reproducible results and to reduce the time for the determination.
Iodide causes an accelerating effect on the reaction, while Fe(III) and Al(III) cause a deccelerating effect even the amounts a few μg levels. The interference by these ions can be eliminated or minimized by an addition of Hg(II) for I^- and of F^- for Fe(III) and Al(III), respectively. The time required for the analysis of one sample is about 50 min and the standard deviation at a manganese level of 50 ng is 3.0%.
Satisfactory results were obtained by the application of the following proposed method to the determination of trace amounts of manganese in high-purity silicon, hydrofluoric acid and nitric acid.
Silicon: dissolve the sample in a mixture of hydrofluoric acid and nitric acid in a platinum dish, followed by an addition of a small amount of sulfuric acid, and expel the acids and silicon tetrafluoride by heating on a sand bath. Add two drops of a mixed solution (HCl+ H₂O₂) and 1 ml of 1 M sulfuric acid. Evaporate to slightly white fumes evolution, cool and then add buffer solution and ammonia water to adjust the pH to 3.8. Manganese is then determined by the procedure described above. Hydrofluoric acid and nitric acid: evaporate the sample with 1 ml of 1 M sulfuric acid to slightly white fuming and manganese is determined by the same procedures in the case of silicon.
By this proposed method manganese as small amounts as 5 ng in the sample (0.5 g of silicon, 5 ml of hydrofluoric acid or nitric acid) can be determined.

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Dissociation constants (pK_a) of calcein which had been purified by recrystallization and reprecipitation were determined by a potentiometric method.
The procedures of purification of the reagent were as follows:
(i) Recrystallization: Commercially available calcein was dissolved in 50% aqueous methanol at 60°C, and residue was filtered off by using low ash filter paper. The filtrate was allowed to stand in an ice bath for 12 days. Crystals formed on the glass wall were collected on a glass filter, washed with methanol and dried in a sulfuric acid vacuum dessicator. (ii) Reprecipitation: The commercially available calcein was dissolved in a small amount of 0.1 NNaOH. The solution was diluted with 510% aqueous methanol, acidified to pH 2.5 with HCl, and allowed to stand in an ice-bath overnight. Crystals formed was treated in the same way as mentioned above.
The paper electrophoresis at pH 7.0 of the purified calcein was compared with that of the raw calcein. The purified samples gave three spots which moved towards the positive side while the raw calcein gave six separate spots; one of them moved towards the negative side, four spots towards the positive side and the other one was immovable. The four, which moved towards the positive side showed fluorescence and the intensity of the spot located in the most positive side was strong but that of the other three was weak. No difference was found in the electrophoresis of the samples prepared by the two purification methods.
Elemental analysis of the samples agreed with the composition, to be C₃₀H₂₆O₁₃N₂. H₂O, and the results of potentiometric titration indicated the purity to be 98%. From these results, the purification of calcein by the above methods was concluded to be enough effective for the determination of pK_a.
Two pH jumps appeared in the titration curve: one in the place of the 2 equivalent point, and the other in the 4 equivalent point. This indicates that each of the protons of the carboxylic and phenolic groups dissociated almost simultaneously. For the determination of pK_a of the carboxylic groups, titrations with 0.1 N KOH were carried out in dioxane solution at various concentrations and the pK_a values obtained were extrapolated to the zero concentration of dioxane. For the determination of pK_a of the phenolic proton and those of amino groups, the sample was dissolved in 0.1 N KOH and back titration was carried out with 0.1 N HCl. The pK_a values which are close to each other were estimated using an equation similar to that presented by Speakman. The values of pK_a1-pK_a6 obtained were 2.1; 2.9, 4.1; 5.4, and 10.1; 12.0 for the carboxylic and phenolic protons and those of amino groups, respectively.
These pK_a values of calcein were compared with those of phthaleine complexon which was synthesized from ο-cresol phthalein, and it was concluded that the two methyliminodiacetic acid groups in calcein substitute the 4 and 5 position, 2 and 5 position or 2 and 7 position of fluorescein.

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The reaction of 5-hydroxychromone with about forty metallic ions has been reported previously. Similar studies were carried out on its 2-and 3-phenyl derivatives, i.e., 5-hydroxyflavone(I) and 5-hydroxyisoflavone (II).
(I) was prepared by the reaction of 2, 6-dibenzoyloxyacetophenone with sodium hydroxide in pyridine by the method of Look et al.⁵⁾, and (II) was prepared by the reaction of 2, 6-dihydroxyphenylbenzylketone with pyperidine and ethyl formate in pyridine by the method of Shah et al. ⁷⁾. The acid dissociation constants (K_a) of (I) and (II) were determined spectrophotometrically to be pK_a =11.3 and 11.7, respectively.
The investigations were carried out on the solutions ranging in pH from 1 to 12, which contained 3 × 10^-7 mol of metallic ion, 3 × 10^-5 mol of the reagent and 50%(vol) of methanol in 25 ml. When precipitation or coloration was observed, extraction of the complexes with the organic solvents such as benzene, chloroform and carbon tetrachloride was attempted. Both (I) and (II) reacted with fifteen metallic ions. The absorption spectra and the effects of pH on extraction of typical complexes are shown in Fig. 2Fig.9. Copper, beryllium, aluminum, titanium, iron(III), and palladium reacted with (I) and (II) to form insoluble complexes, which could be extracted into organic solvents and were stable for at least three hours. The molar absorption coefficients of these complexes extracting into suitable organic solvent were of the order of 10⁴. The complexes of beryllium, aluminum and titanium were fluorescent. Cobalt and nickel formed also precipitates with these reagents, but the complexes of (II) only could be extracted into organic solvents. Magnesium, gallium, zirconium, thorium, antimony (III) and uranium reacted with (I) and (II) to form yellow insoluble complexes, but extraction of them was incomplete or impossible. Tin(IV) formed yellow soluble complexes with (I) and (II). They could be extracted into organic solvents, but their absorbances were small. The stability constants of their iron(III) complexes with molar ratio 1: 1 were determined spectrophotometrically. The results are shown in Table I.
The following conclusions can be reached on the basis of the experimental results; (1) Similar kinds of metallic ion form the complexes with (I), (II) and 5-hydroxychromone. (2) The extractability of the complexes of (I) and (II) is slightly superior to that of the complexes of 5-hydroxychromone. (3) The maximum absorption wavelengths of the complexes of (I) are shifted a little to the longer wavelength comparing with those of the complexes of (II) and 5-hydroxychromone which have similar peaks. (4) The absorbances of the complexes of (I) are greater than those of the complexes of (II) and 5-hydroxychromone which are nearly equal. (5) (I) and (II) have nearly equal pK_a and log K₁{K₁: stability constant of 1: 1 iron (III) complex} and these values are slightly larger than those of 5-hydroxychromone.

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There are many halogen-containing compounds, which were classified into three groups tentatively, that is, the drugs containing 1) ionic halogens, 2) non-ionic halogens, and 3) both ionic and non-ionic single halogens. Quantitative determination of halogens in drugs were carried out by atomic absorption spectrophotometry and satisfactory results were obtained.
The recommended procedures are as follows: Samples containing ionic halogens, such as, guanidine hydrochloride and propantheline bromide, were dissolved in water. It was found that desirable concentrations of the sample solutions were 25 μg/ml for Cl-containing drugs, and 100 μg/ml for both Br-and I-containing drugs for the measurements, respectively.
Then, proper amounts of the sample solution (14 ml) was made acidic with nitric acid, being followed by the addition of 5 m/ of 100 μg/ml silver nitrate solution, and the resultant solution was warmed on a water-bath for 1 min. It was kept standing for 30 min at a room-temperature, the precipitates were filtered off and the filtrate was diluted to 100 ml with water, then excess amounts of silver were determined by atomic absorption spectrophotometer. Samples containing non-ionic halogens, such as bromisovalum and iodoform, were fused with metallic sodium of 1020 times as much as the samples taken and after the decomposition of excess metallic sodium unreacted with water, the residues were filtered off and the filtrate was used as a sample solution. Following procedures were similar to those of ionic halogens. Standard solutions of Cl, Br, and I for the working curves were prepared by the similar procedures.
In order to ascertain the repeatability of samples in different contents of halogens, the amounts of which were determined and the standard deviation was calculated to be 0.150.67. Other metal ions (Na⁺, K⁺, Cu²⁺, Mg²⁺, Ca²⁺, Al³⁺, Bi³⁺) did not interfere with chlorine determination, even in the coexistence of about 30 times as much in concentration. Moreover, among the anions reactive with silver ions, removal of coexisting sulfur in a sample was studied. For the quantitative analyses of both sulfur-and halogen-containing drugs, silver sulfide was precipitated together with silver chloride in acidic solution. Therefore, in order to remove sulfur as cupric sulfide, excess amounts of cupric nitrate solution (1 mg/ml) was added to the alkaline solution resulted from metallic sodium fusion. Precipitates of cupric sulfide and cupric hydroxide were filtered off, and the filtrate was treated in the same manner as described above.
It has been found that this method, its procedure being very easy and simple, can be made use of even for a small amount of samples (0.251.25 μg Cl/ml, 0.53μg Br/ml, 15 μg I/ml), and so it is applicable to the quantitative determination of halogen-containing drugs.

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The thiochrome formation by the reaction of thiamine with mercuric oxide was quite sensitive, and the resulted thiochrome showed strong fluorescence. Therefore, the above reaction was applied to the determination of micro amounts of mercury, since both mercuric and mercurous ions were found to form mercuric oxide in alkaline medium, and to react with thiamine.
5 ml of sample solution containing 0.258.00 μg of mercury was shaken with 1 ml of either 0.5 or 5.0 μg/ml of thiamine reagent depending on the quantity of mercury in the sample solution. After shaking them, 4 ml of sodium hydroxide-borate buffer at pH 9.5 was added to the above mixture, and the whole solution was further shaken for 1 min. Furthermore, after being heated for 5 min, in a boiling water bath, the solution was cooled in an ice bath. As the salting-out reagent, 3.5 g of sodium chloride was dissolved in the solution, and then the thiochrome produced was extracted with 6 ml of iso-butyl alcohol. The intensity of the fluorescence in the iso-butyl alcohol at 430 nm excited by 375 nm rays was then measured using quinine sulfate solution as the reference.
Calibration curves were obtained in the range of 0.051.60 μg/ml of mercuric ion, and in the range of 0.201.60 μg/ml of mercurous ion. By comparing the intensity of fluorescence of mercuric and mercurous ions, it was found that the former showed stronger fluorescence than the latter.
Interference by diverse ions with this method was studied in the mole ratio range from 10 upto 1000 of the testing ion to 1 μg of mercuric ion. Cations and anions such as Ag⁺, Sn²⁺, Bi³⁺, Fe³⁺, I^-, S₂O₃^2-, SO₃^2- S^2-, Fe(CN)₆^4-, Fe(CN)₆^3-, MnO₄^-, CrO₄^2-, and Cr₂O₇^2- were found to interfere more or less with the thiochrome formation, and hence with the determination of mercury. The cations and anions; Pb²⁺, Cd²⁺ Cu²⁺, Fe²⁺ Co²⁺ Ni²⁺ Mn²⁺, Cr³⁺, Ba²⁺, Mg²⁺, Ca²⁺, Cl^-, Br^-, SO₄^2-, NO₃^-, NO₂^-, acetate, tartrate, and citrate, on the other hand, gave no interference with the determination.
From these it was concluded that in the absence of interfering substances, the sensitivity of this method is expected to be about ten times greater than that of the ordinary colorimetric method with dithizone, and the limit of determination of mercuric and mercurous ions were 0.05, μg/ml and 0.20 μg/ml, respectively.

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The focusing chromatography separation of radioactive alkaline earth and rare earth elements with potassium fluoride as a precipitation reagent was investigated. The experiments have been carried out with hydrochloric acid contained in the positive electrode cell and with a dilute aqueous solution of potassium fluoride contained in the nagative electrode cell. Fundamental factors such as the duration of the electrophoresis, pH value, the concentrations of the potassium fluoride solution and the hydrochloric acid, etc. were examined.
The sample solutions were 0.01 M hydrochloric acid containing a tracer amount of either barium-140 (containing lanthanum-140), strontium-90 (containing yttrium-90) or cerium-144(containing praseodymium-144). Each of these nuclides was carrier free, and the activity of each solution was 1 μ Ci/ml. The separated radioactive bands on the paper chromatogram were located by autoradiography. According to the detected positions, the filter paper was cut into pieces and the species of the radionuclides were determined by γ-ray spectrometry and the measurements of the energies and the half-lives of β-rays.
The present method gave good results for focusing and separating cerium-144, barium-140 or strontium-90 from the daughter nuclides, praseodymium-144, lanthanum-140 or yttrium-90, respectively. Moreover, this procedure was effective for the separation of alkaline earth group from rare earth group. The optimum separation was obtained by using 0.05 M hydrochloric acid in the positive cell, 0.05 M solution of potassium fluoride(buffered with sodium acetate) in the negative cell, the pH of which was 5.25.7, intensity of the electric field being 500 V/26 cm and migration time being 10 minutes. The mechanism of separation was thought to be as follows.
On the electrophoretic paper strip, the metal ions in the sample migrate into the potassium fluoride solution fed by the negative cell until the product of concentration of each metal ion and that of fluoride reaches its solubility product, so that position of the deposited fluorides on the paper strip are determined by their solubility products and their mutual separation is more effective.

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Potentiometric titration of ethylenediaminetetraacetic acid (EDTA) with lead tetraacetate was investigated.
The titration procedures are as follows. An aqueous solution (100 ml) containing 40 ml of glacial acetic acid, 2 ml of 4 M sodium acetate, and 10.00 ml of 0.05 M lead tetraacetate in glacial acetic acid, was titrated with a standard EDTA solution by using a platinized platinum wire electrode as indicator electrode. The potential of the electrode was measured against a saturated calomel electrode, which was connected to the solution through an agar bridge of 30% KNO₃. The measurement of the potential was made at 2 minutes after each addition of the titrant.
The end point indicated that Pb(IV) ion reacts with EDTA in molar ratio of 1: 1. The potential change in the vicinity of the end point was about 50 mV per 0.10 ml of the titrant. EDTA could be determined over the concentration range of 0.020.05 MM within the error of ± 1.0% and within the relative standard deviation of ± 0.1%. The addition of Pb(II) ion into the titrated solution up to 2% of the concentration of Pb(IV) ion did not interfere with the determination. Interference of Pb(II) ion with the determination was observed, as shown in the two-stepped titration curves in Fig. 7 when its concentration was larger than 2% of that of Pb(IV) ion in the titrated solution. The conditional formation constant of the chelate of Pb(II) ion with EDTA was calculated to be about 10⁴ M^-1 under the experimental condition.
Effects of the change in the concentration of acetic acid or sodium acetate and temperature of the titrated solution were examined.
When the concentration of acetic acid in the titrated solution increased to 90 vol. %, the potential break became too indistinct to be used for the determination of EDTA, as shown in Fig. 4. When the concentration of sodium acetate in the titrated solution decreased to less than 0.08 M, a negative error was remarkable as shown in Table III.
When the temperature of the titrated solution was higher than 25°C, a negative error was noted as shown in Fig. 6.
It was considered that the potential of the indicator electrode beyond the end point of the titration curve would be determined predominantly by the platinum ion-platinum system, which was produced by the dissolution reaction of the platinum oxide layer in excess EDTA (Fie. 9).
The present potentiometric method is as satisfactory for the standardization of EDTA as the indicator method.

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The design and performance of a selective gaschromatographic detector for nitrogen compounds have been described. The principle of detection is based on the continuous monitoring of ammonia absorbed in an absorption solution by means of a monovalent cation-sensitive glass electrode preventing any interference from other common elements.
Components in the sample are separated on a gas chromatographic column using hydrogen as carrier gas. Individual components from the column are passed through a quartz tube packed with a nickel catalyst and heated at 820°C. Under these conditions, the nitrogen in nitrogen compounds is converted into ammonia. The gas mixture produced by decomposition is introduced into an absorption tube, in which the ammonia is absorbed in a slow stream of a buffer solution. The resulting solution emerging from the absorption tube is passed through a flow-cell with a monovalent cation-sensitive glass electrode. Changes in the ammonium ion concentration in the solution are detected by the corresponding changes in the ion electrode potential. The difference in the potential between the ion electrode and the reference electrode is fed to an antilog converter circuit and a signal directly proportional to the ion concentration is recorded. A chromatogram showing only peaks due to nitrogen compounds is obtained.
Various samples containing nitrogen compounds (nitrile, thiocyanate, heterocyclic and nitro compounds) were chromatographed. It was shown that selective detection of nitrogen compounds can be achieved and the ratios of the peaks areas of these components are proportional to the number of nitrogen atoms in each molecule. The response of this detector to the nitrogen containing compounds was about 2000 times of that to an equal quantity of chlorine compounds and was much larger than this for other compounds. The limit of detection was about 5 × 10^-10 moles for nitromethane at a signal-to-noise ratio of 2. The response was linear for 5 × 10^-10 to 1 × 10^-7 mole of nitromethane. An example of the utility of the detector was demonstrated in the analysis of a mixture of pesticides. The full scale response was obtained for Diazinon (C₁₂H₂₁N₂O₃PS) while other pesticides containing chlorine and oxygen were not detectable.

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A method of spot analysis for mercuric compounds has been proposed, by using a reaction of mercuric ion and hydroquinone to form a blue ring on a thin layer of kieselguhr (or filter paper).
Five μl of the acidified (0.52N with respect to nitric acid) test solution is placed on a kieselguhr layer (Keiso layer G). After drying, about 5 μl of 3% aqueous solution of hydroquinone was spotted with a glass capilary tube. A light yellow stain was appeared when the spot was dried at 6070°C by hot air.
Subsequently, about 5 μl of 1 N hydrochloric acidaceton (1: 1 v/v) was spotted. Then a blue ring appears if mercuric salt is present. This method was not interfered with the reaction of common metal ions. When carried out as a spot analysis on kieselguhr, the test is more sensitive than other layers and filter paper limit of identification on kieselguhr layer; 10 μg Hg/5 μl. Therefore, this reaction serves as a practical use for the detection of mercuric compound. In addition, it was proved that the effect of spot chromatographic separation is an important factor when this method was applied to the mixture.

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Analysis of lead and cadmium fume, particularly the method to capture their fume, was studied. The experiment was performed by a combination of an impinger method that is used for water, nitric acid, and sulfuric acid, and a filter sampler method. Result: the impinger method couldn't capture the fumes completely, but the filter caught than 99.5% of them. Use of 1 or 2 pieces of glass fiber filter, or 2 or 3 pieces of No. 6 filter paper was effective. From an observation of the fumes by an electronmicroscope, it was known that these fume perticles join each other as a chain than, they are caught by filters easily. Their analysis was made by atomic absorption spectrophotometry.

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Differential titration and potentiometric titration, and C. Winkler's method have often been used for the determination of sodium hydroxide and sodium carbonate in brine. However, those water samples containing small amounts of minerals and brine, have buffering capacity against an addition of hydrochloric acid, and therefore the former methods are unsuitable for the determination of them.
An investigation has been made in. this paper on the application of a fluorescence method for the analysis of sodium hydroxide and carbonate (sodium alkali) in brine. This method based on the fluorescence due to the reaction between ο-phenylphenol and the sodium alkali under ultraviolet rays. The fluorescence intensity is very stable, and by this simple and rapid method proposed here, sodium hydroxide and sodium carbonate in brine can be satisfactorily analysed. Calcium chloride and magnesium chloride give no influence, and one sample can be analysed within about 30 minutes with an accuracy enough for practical use. The limits of the determination of NaOH and Na₂CO₃ are 0.4 mg/l in both cases.

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In order to estimate the AC polarographic peak height three methods have been proposed, i.e., upper end, middle point and lower end methods in which the peak height is evaluated from the length of the respective vertical line as illustrated in Fig. 1. In this report, the fitness of the three methods for obtaining calibration curve were compared statistically by means of the cor-relation analysis.
AC polarograms were recorded for Cu²⁺, Pb²⁺ Cd²⁺ and Zn²⁺ under the usual conditions, as given in Table I, and the peak heights thereof were measured according to the three methods and the corresponding three working curves for each metal ion were constructed. The least squares method was applied to draw each working curve. It was found that there is no significant difference between the linearities of three calibration curves for each depolarizer.
It was confirmed that the upper end method is best for the estimation of the AC peak height because of its simplicity of construction and the steapness of calibration curve, as formerly reported by Itsuki and Suzuki.

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