Arsenic was determined by atomic absorption spectrometry with a high sensitivity and presision by using the arsine generation method. A slightly modified and simplified D.C. Maning's apparatus was used and no special device was required.
The sample solution (3 M HCl) was treated with potassium iodide solution, stannous chloride solution and zinc powder. The generated arsine was led to the burner by argon and atomized with H₂-argon (entrained air) flame. The effects of the reductant, zinc powder, the concentration of hydrochloric acid and diverse ions were examined. The most effective reductant was stannous chloride solution combined with potassium iodide solution. The absorbance was constant when the volume of the stannous chloride solution (200 g/l) was between 2 ml and 5 ml and that of the potassium iodide solution (200 g/l) was between 1 ml and 5 ml. The profile of absorbance was satisfactorily sharp with the use of abqut 200 mesh zinc powder and absorbance was decreased when the powder of greater particle size was used. The absorbance was constant in the concentration range of hydrochloric acid between 2 M and 5 M. Ten milligrams of copper, iron, nickel and antimony ions 2 g of sodium chloride and 200 mg of nitric acid were tolerable. The recommended procedure for determination of arsenic in soils are as follows.
Take 0.1 g of air-dried sample in a Griffine beaker and add 2 ml of perchloric acid, 2 ml of nitric acid, 5 ml of hydrochloric acid and 2 ml of sulfuric acid (1+1). Heat gently until the decomposition completes, then evaporate to dryness. After cooling, add 10 ml of hydrochloric acid and heat to dissolve the residue. Transfer the solution into a volumetric flask (200 ml). Adjust the volume to 200 ml with water and introduce 10 ml portion of the diluted solution into the generator. Add 10 ml of hydrochloric acid, 3 ml of sulfuric acid, 1 ml of potassium iodide solution (200 g/l) and 2 ml of stannous chloride solution (200 g/l), and let stand for 10 minutes. Add 1 g of zinc powder and immediately connect the generator to the atomic absorption spectrometer. Measure the absorbance of resonance line of arsenic at 193.7 nm.
The standard deviations of this method were 0.0000.003 ppm at the level of 0.0040.083 ppm for waste water and 0.00010.0002% at the level of 0.00140.0036% for soils. Sensitivity was 0.02 μg (1% absorbance).

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Isotope dilution mass-spectrometry can be applied to the determination of minute amounts of calcium in distilled water, deionized water and snow melts from ice sheets in Greenland and Antarctica. The amount of sample required is 20 g for snow analysis.
In a 100 ml teflon beaker, 0.3×10^-7 M of ⁴²Ca spike in 0.06 g of dilute nitric acid is accurately weighed. Snow melt is poured directly into the beaker from the agitated sample bottle and is weighed. The mixture is evaporated to 50 μl in a heated steel tank in which high purity nitrogen gas is streaming. Small drops of the concentrated liquid are loaded onto the tantalum filament by using a quartz micropipette.
The ion source used is equipped with a specially designed single filament unit which is heated with accurately controlled electric current. This emits intensive Ca⁺ beams from 10^-10 g of calcium salts loaded on the filament.
The coefficient of variation for the peak height ratio of ⁴²Ca to ⁴⁰Ca ranges between 0.22 and 0.66 percent and is not affected by the coexistence of foreign substances. The degree of isotope effects is reduced to a minimum under 1 percent by running the mass-spectrometer under common conditions. Calcium and potassium have the isobars with the mass number of 40, but the isobar effects can be reduced to a negligible quantity by baking treatments.
Snow melts contain minute amounts of silicate mineral dusts which have played important roles as the nucleation centre for water vapour at the formation of snow flakes. So it is important that calcium added as a spike is equilibrated isotopically with that in the silicate mineral dusts. If it is not so, calcium isotopes ia a salt matrix may be more easily released from the heated filament than those combined with the silicate matrix, and this will result in lower value of calcium. From the content of titanium, calcium from the silicate mineral dusts accounts for nearly 10 percent of total calcium in snow melts, while the remaining calcium occurs in sea salts predominantly.
The concentrations of calcium are found to be 1.9 ppb in both redistilled and deionized water, 2 ppb in snow melts of West Enderby Land, Antarctica, and several ppb in those of Camp Century, Greenland. In greenland snow strata, calcium concentrates in winter layers as well as dusty components. In both the polar regions, no appreciable variations of calcium concentration have been detected in whole year composite samples since 1750.

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The carrier gases usually used in gas chromatography (GC) are permanent gases, while in some cases the vapor of carbon tetrachloride, benzene or steam as carrier gas has been recommended in the analysis of polar compounds and in the measurement of gas diffusion coefficients between organic vapors.
This study attempts to use ethanol vapor as carrier gas and activated alumina as solid adsorbent in GC and examines the analysis of aromatic compounds and ketones. The alcohol was fed to a heated tube by a micro feeder and vaporized; the vaporizer was made by modifying a GC injector part. The effluent vapor from the separation column was condensed in a small condenser, the liquid containing the sample components was led to a UV adsorption detector (Laboratory Data Control, Inc.). The volume of the liquid cell of the detector is 8 μl and its path length is 10 mm. Several kinds of activated alumina (3060 or 200300 mesh) supplied by Kishida Kagaku, E. Merck and other makers were used.
By using this method, mixtures of benzene, p-xylene, di-n-propyl ketone and naphthalene, of benzene, naphthalene, diphenyl and anthracene, of ketones, etc. were separated. When 0.15 ml of town gas was injected into the column, olefins were also detected. p-Terphenyl, chrysene and dinitrobenzenes were also analysed. The minimun detectable amount except for ketones and olefins was 101 ng. Height equivalent to the theoretical plate of the column is about 1 cm for activated alumina of 3060 mesh, and about 0.3 cm for that of 200300 mesh.
The effect of the composition of ethanol-hexane carrier system on the retention volumes (R_v) of benzene and methyl isobutyl ketone was examined. When the mole fraction of ethanol decreased from 0.02 to zero, R_v of benzene increased only slightly, while R_v of methyl isobutyl ketone increased about ten times.
The effect of carrier gases of ethanol and nitrogen on the retention volumes of benzene was also examined. R_v of benzene using nitrogen as carrier gas was about 100 times of R_v of it using ethanol vapor as carrier gas.
It is suggested that in this chromatography ethanol vapor is adsorbed on the surface of activated alumina and forms a thin layer of liquid.

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Titanium, vanadium and iron ions form colored complexes with pyrogallol in acetate buffer solution. The titanium complex is orange at pH 3 and yellow at pH 6.5. The vanadium complex is dark blue at pH 6.5 and colorless at pH 3. The iron complex is red violet at pH 6.5 and colorless at pH 3 and when it is masked with EDTA at pH 6.5. At about 600 nm the vanadium complex has a maximum absorption, while the titanium complex is found to have little absorption in this range. The absorbance of the titanium species is equal to zero at 610 nm. The above principle is used for the simultaneous determination of titanium, vanadium and iron.
The experimental procedure is as follows: An aliquot of the sample solution of titanium, vanadium and iron containing below 200 μg, 150 μg and 250 μg of each metal ion is transferred to a 50 ml volumetric flask. The pH of the solution is adjusted to 3.0 (±0.1) with the acetate-oxalate-sulfite buffer solution. Dilute the solution to volume with water. The absorbance is measured at 410 nm against a reagent blank where the titanium alone is determined.
Then, the pH of another aliquot of the sample solution is adjusted to 6.5 (±0.1) with the acetate-sulfite buffer solution and add 30% pyrogallol. Dilute to the mark with water and measure the absorbance (A) of the solution at 610 nm. The third aliquot of the sample solution is transferred to a 50 ml flask. After the treatment of the above procedure, EDTA solution is added to mask iron, after dilution to the mark and on standing for 70 minutes, absorbance (B) is measured. at 610 nm. The concentration of vanadium that corresponds to B is obtained from the calibration curve of vanadium. The concentration of iron that corresponds to the absorbance (A-B) is obtained from the corrected calibration curves for iron.
Besides, after masking of iron at pH 6.5, titanium and vanadium can be determined simultaneously, by measuring the absorbances at 410 nm and 610 nm and solving the two spectrophotometric equations.
This method could be applied for the simultaneous determination of synthetic sample solutions containing 25?200 μg of titanium, 40?150 μg of vanadium and 50?250 μg of iron in 50 ml within 3% of relative error.
The mole ratio of iron to pyrogallol in the complex was 1 to 1. It was confirmed that the composition of titanium and vanadium in the presence of excess pyrogallol and ammonium oxalate in the acetate buffer solution was 1:2 (Ti:pyrogallol) at pH 3 or 6.5 and 1:1 (V:pyrogallol) at pH 6.5, while the composition of titanium and vanadium in the absence of ammonium oxalate was 1:1 (Ti:pyrogallol) and 1:2 (V:pyrogallol).

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Oxygen in fluorine compounds could not be determined by a usual oxygen determination apparatus with a silica decomposition tube. Hydrogen fluoride resulting from the thermal decomposition of a sample reacts with the wall of the silica decomposition tube. By that reaction, water is produced and the quantity is added to that of oxygen to be determined. Therefore, a platinum decomposition tube can be used instead of a silica decomposition tube.
The authors used a platinum decomposition tube and determined oxygen and fluorine in fluorine compounds simultaneously. The wide portion of the platinum decomposition tube is 8 mm in outside diameter, 7.6 mm in inside diameter, 0.2 mm in thickness, 450 mm long, and the narrow portion 5 mm o.d., 50 mm long.
The procedure is as follows. The flow rate of nitrogen is 15 ml/min. Oxygen is removed from the nitrogen by a layer filled with porous copper heated at 500550°C. Carbon 100 mm long(it is 1520 mesh, after treatment with hot hydrochloric acid) is packed into the platinum decomposition tube, and both side of the tube are sealed with carbon fiber. This layer is heated at 1100°C by a silicon carbide furnace. The platinum decomposition tube is mounted in the silica tube 400 mm in length, 30 mm o.d., 24 mm i.d. and purified nitrogen is flowed into the space. The narrow portion of the platinum decomposition tube is connected to a silica tube (50 mm long, 5 mm o.d.) filled with silica wool. A sample is weighted in a platinum boat and heated at 900°C in the platinum decomposition tube. Products produced by the thermal decomposition of a sample pass over carbon at 1100°C, the oxygen of the sample is then converted to carbon monoxide, and the fluorine of the sample is converted to hydrogen fluoride. The carbon monoxide does not react with silica wool filled in the silica tube. Hydrogen fluoride reacts with silica wool filled in the silica tube to give silicon tetrafluoride and water. They are absorbed in the tube filled with silica gel and magnesium perchlorate. An increased value in weight of the tube is multiplied by a conversion factor of fluorine and the content is calculated. The factor for fluorine is 4F/SiF₄·2H₂O=0.5424. Carbon monoxide is oxidized to carbon dioxide by iodine pentoxide at 150°C. This is absorbed in the small carbon dioxide absorption tube filled with sodium hydroxide and magnesium perchlorate for carbon-hydrogen determination. An increased value in weight of the tube is multiplied by a conversion factor of oxygen and the content is calculated. The factor for oxygen is O/CO₂=0.3636. The fluorine content of a sample is calculated by (%)=0.5424×(a-b)×100/s. The oxygen content of a sample is calculated by (%)=0.3636×(a'-b')×100/s, where s: weight of a sample (mg), a: an increase in weight of the tube for fluorine, b and b': the blank value, a': an increase in weight of the tube for oxygen.
About 3 mg of sample was used and the entire determination took about 4550 min. The blank value of the tube for oxygen was about 50 μg and that of the tube for fluorine was about 30 μg. The error of this method was ±0.4% for oxygen and ±0.3% for fluorine.

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Heated porous copper can remove oxygen from air, and the deoxygenated air can be used as carrier gas of oxygen determination. The optimum conditions for removing oxygen from air and for oxygen determination using deoxygenated air as the carrier gas are investigated.
The porous copper was prepared from the active copper powder of about 40 μm in diameter by the activating-sintering method at a low temperature. The porous copper was non-cellular type of apparent density about 1.1 g/cm³ with porosity of 87% and specific surface area of about 500 cm²/g.
A 200 mm portion of a sillica tube (330 mm in length, 22 mm in inner diameter, 28 mm in outer diameter) was filled with 130 g of the porous copper, through which dry air was passed at a rate of 15 ml/min. The oxygen content of the resultant gas was fed to an oxygen determination apparatus {See Bunseki Kagaku, in preparation}.
The porous copper becomes active at about 180°C, and at 320°C the deoxygenated air can be used as carrier for the oxygen determination apparatus. When heated at 500550°C, a sample of 130 g of the porous copper absorbed 30.1 g of oxygen (92% of the theoretical capacity) before the limit of durability was reached. The porous copper can be re-activated repeatedly by reducing it with town gas at about 400°C or with hydrogen at 200°C. If air is passed at a rate of 15 ml/min for 8 hours per day, 130 g of porous copper remains active about 15 days. There was no difference between the content of residual oxygen in the deoxygenated air and that in commercial nitrogen purified by the porous copper.
Oxygen contents of sucrose, benzoic acid, p-chlorobenzoic acid, acetanilide, p-bromoacetanilide, p-chloroacetanilide, 4'-ethoxyacetanilide, cholesterol, 2, 2-bis(ethysulfonyl)-propane were determined. The experimental error of oxygen was ±0.3%. The entire determination took about 35 min by the gravimetric analysis and 78 min by the coulometric analysis.

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The complex formation between dihydroxyethylglycine (2-HxG) and lanthanide ions was investigated by potentiometric titration. The existence of metal ion-2-HxG complexes of the composition 1:1 and 1:2 was shown by the analysis of the titration curves.
Titration curve of 2-HxG and those in the presence of La(III) and of Gd(III) in the ratio 2:1 are plotted in Fig. 1-b (the volume of added potassium hydroxide were corrected for the amounts of base consumed by the neutralization of strong acid present in the metal ion solutions). These titration curves show one inflexion at a=1.0 (a is the equivalent base added per mole of ligand) (refer to Fig. 1-b). Typical formation curve of 1:1 and 1:2 La(III)-2-HxG complexes, the relation between pA=-log [A] and n (where [A] is the concentration of free 2-HxG and n is the average co-ordination number), are shown in Fig. 2 a and b (Bjerrum's method). The Bjerrum formation curves of other lanthanide ions {M(III)=Ce, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm} are similar.
The Stability constants referring to the corresponding complex formation equilibrium (M³⁺+AH+OH^-_??_MA²⁺+H₂O) are reported. The trend revealed by the plots of the logarithmic stability constants (log K₁) of the lanthanide complexes against the atomic number (Fig. 3), closely resembles that of the fourth class of Yatsimirskii's classification: the stability constants increased with the atomic number for La(III) through Gd(III) but decreased for Tb(III) through Tm(III). It was found that the separation of heavier lanthanides from the lighter ones would be possible.
The similar behavior of the stability constants have been shown for the lanthanide complexes of acetate, glycolate, gluconate, dipicolinate and N-hydroxyethylenediamineacetate. Fifty available data of stability constants of lanthanide complexes were treated statistically according to Kumok's method and the following relation was found to exist.
log β_Ln=a log β_La+b
where β_La and β_Ln are the stability constants of the lanthanum and other lanthanide complexes, respectively. The parameters a and b in the equation of the principal straight lines are shown in Table I. The stability constants obtained in the present experiments (the fourth column) are shown in Table I together with the values calculated on the basis of the above equation (the seventh column), where the agreement between the two sets of values is apparent.
The structures (I) and (II) of the complexes was shown in Fig. 4 and was discussed.

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Lead ions react with potassium ethyl xanthate(KEtX) to form a white complex, which can be extracted quantitatively into methyl isobutyl ketone(MIBK) from aqueous solution at pH 3.59.5. Reaction molar ratio of lead xanthate was Pb(II): KEtX=1:2 as determin-ed by the continuous variation method. Small amounts of lead can be determined by submitting the extract to atomic absorption spectrophotometry. The experimental condition of the atomic absorption spectrophotometry was as follow: wavelength, 2833.0 Å; the current of hollow cathode lamp, 5.0 mA; slit width, 100.0 μm; air flow rate, 7.0 l/min (2.5 kg/cm²); acetylene gas flow rate, 1.0 l/min (0.3 kg/cm²).
Copper(II) (>50 μg/ml) and phosphoric acid (>200 μg/ml) interfered with the extraction, but silver(I), cadmium (II), zinc (II), chromium ( III), manganese-(II), nickel(II), mercury(II), aluminum(III), cobalt-(II), iron(III) and anions except phosphate did not. Copper ion can be masked by the addition of an appropriate amount of thiourea. The sensitivity limit of this method was 0.12 (μg/ml MIBK)/1% As without scale expansion. The determination of lead in human tissues (lung, liver, pancreas, kidney and stomach decomposed by wet digestion with nitric acid and perchloric acid) were performed successfully.
The general procedure was as follow. Take an aliquot of sample solution into a separatory funnel, add 10 ml of 10% ammonium citrate as buffer solution and 5 ml of 5% KEtX as chelating agent, and adjust pH to 5.56.0 with ammonia water. Adjust the final volume of the aqueous phase to 30 ml by the addition of metal free water (the volume of the aqueous phase must be constant because of co-solubility of MIBK and water). Extract lead xanthate with 5 ml MIBK by shaking for 3 minutes, and determine lead in the separated organic phase by atomic absorption analysis. The sensitivity and accuracy of the present method were similar to those of the method using ammonium pyrrolidine dithiocarbamate. The standard deviations of both methods were 0.060.17 μg/ml.

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Neutron activation analysis is applied to determine 17 trace elements in human head hair. After neutron irradiation, hair samples emit intense gamma rays of ²⁴Na and ⁸²Br induced from sodium and bromine contained in the sample. Therefore, in the conventional non-destructive activation analysis, it is not possible to determine accurately the contents of elements which. produce short lived nuclides, because of the interference with the Compton back ground and photopeaks from ²⁴Na and ⁸²Br.
In this study, low temperature ashing technique was employed, and it was effective for the removal of bromine from the sample. The ashing was carried out for 15 hours at a high-frequency output power of 150 W and an oxygen flow rate of 80 ml/min. The ash was irradiated for 3 days (6 hours/day) in TRIGA Mark II Reactor of Rikkyo University with a neutron flux of 5×10¹¹ neutrons per square centimeter per second. After the irradiation, the sample was dissolved in hydrochloric acid. The induced ²⁴Na activity was completely removed by passing the solution through a HAP (hydrated antimony pentoxide) column.
Seventeen trace elements, Ag, As, Au, Cd, Co, Cu, Fe, Ga, Hg, In, La, Mn, Ni, Sb, Se, Sr, and Zn, were determined. Time required for the determination was reduced from 42 days to 11 days as compared to the non-destructive activation analysis reported by Perkons and Jervis {Proc. Modern Trend in Activation Analysis, Texas, p. 295 (1965)}.
Ashing test of filter paper impregnated with 17 elements shows all the elements except bromine and mercury can be quantitatively recovered.

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Molybdenum reacts with stilbazo in the presence of zephiramine to give a water-soluble red complex. Its absorption maximum is at 535nm, and the absorbance shows a roughly constant value at pH 3.64.2, but the maximum absorbance has at pH 5.2, although the pH range for the constant absorbance was not obtained. Therefore, molybdenum is determined at 535 nm and pH 3.9. A liner calibration curve is obtained up to 32 μg of molybdenum in a 50 ml solution. The apparent molar absorptivity of this complex is found to be 6.35×10⁴; The concentration of molybdenum corresponding to the absorbance (log-I₀/I) of 0.001 is 0.0015 μg/cm².
L-Ascorbic acid solution was added in advance to remove the interference of iron (III).
Aluminum, gallium, vanadium(IV, V), titanium, zirconium, wolfram, paradium, lead and perchlorate interfered seriously with the determination, but aluminum, vanadium and titanium of the same order of magnitude as molybdenum could be masked by the addition of ammonium fluoride, and the interfering zirconium was also masked with ammonium fluoride. However, wolfram was not masked with it.
This reaction was applied to the determination of molybdenum in iron and steel.
The proposed procedure is as follows; 0.050.1 g of a steel sample was decomposed with 5 ml of HCl (1+5) and 56 drops of HNO₃ with slightly heating on a sand bath, and it was evaporated, but the residue not ignited. The contents were dissolved with 10 ml of 0.5 N HCl. The solution was transferred to a 100 ml volumetric flask and diluted to the mark with water.
In case of the stainless steel, the sample was decomposed with 4 ml of aqua regia, and then 6 ml of H₂SO₄(1+5) was added. It was heated until the fume of sulfuric acid was evolved. Upon cooling add 2030 ml of water, and boil to dissolve the contents. Cool the solution and filter it into a 250 ml volumetric flask, and diluted to the mark with water.
A 5 ml(or 2.5 ml) aliquot was transferred into a 50 ml volumetric flask, and then 5 ml of 5% ammonium fluoride, 1 ml of 10% ascorbic acid, 10 ml of the acetate buffer solution (pH 3.9), and 1 ml of 0.05% stilbazo solution were added. This solution was made up to about 45 ml with water, and then 2 ml of 0.5% zephiramine was added, and diluted to the mark with water.
The solution was taken into a 1 cm cell and the absorbance was measured at 535nm within two minutes against a reagent blank.
Analytical results of the standard samples of iron and steel by this method were satisfactory, and furthermore this method could be applied except the steel sample containing wolfram.

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A higher sensitive method of the spectrophotometric determination of small amounts of vanadium with 2-(2-thiazolylazo)-5-dimethylamino-phenol (TAM) extracting into chloroform from an acidic solution is studied.
The established procedure is as follows; Take an aliquot of the sample solution containing less than 10 μg of vanadium into a 200-ml separation funnel. Add 1.0 ml of TAM-methanolic solution, adjust pH of the solution to 4 by adding 1 M sodium acetate-1 M hydrochloric acid buffer solution and dilute to 50 ml with distilled water. After 15 minutes, extract vanadium-TAM complex into chloroform from the aqueous solution by shaking for 30 seconds, and transfer the organic phase into a 1 cm cell to measure the absorbance at 595 nm against a reagent blank.
The complex of vanadium is extracted quantitatively into chloroform from the aqueous solution at the pH range from 3.5 to 4.3. The vanadium-TAM complex is extremely stable and shows an absorption maximum at 595 nm. The molar extinction coefficient of the complex at this wavelength is estimated to be 4.2×10⁴ and the sensitivity for vanadium is 1.2×10^-3 μg/cm² per 0.001 of an absorbance. Beer's law is obeyed up to 1.2 μg/ml of vanadium. The molar ratio of vanadium to TAM in the complex was confirmed to be a 1:1 ratio by the method of continuous variation.
The interferance with coexisting ions on the absorbance of the complex of vanadium was examined. Titanium(IV), niobium(V), zirconium(IV), iron(III) and oxalate ions negatively interfere with the determination. Niobium and iron ions can be masked by the addition of 0.5% potassium cyanide and 10% triethanolamine, respectively.
The established method was applied to the determination of small amounts of vanadium in carbon steel by combining with methyl isobutyl ketone extration. After the treatment of the extracted solution with sulfuric acid, the solution was made up to 500 ml with distilled water. Take an aliquot of the sample solution into a 100-ml beaker and add 2.0 ml of 0.5% potassium cyanide, and the solution is used for the spectrometry described above. The coefficients of variation by the present method were 1.0% for carbon steel (V content 0.10%).

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In previous papers, we reported the preparation of silica gel, alumina, and Kieselguhr sintered plates, on which various classes of organic compounds were separated successfully.
The present report describes the fluorescent sintered plates consisting of manganese-activated zinc orthosilicate, tin-activated strontium pyrophosphate or europium-activated yttrium vanadate as fluorescent indicator, and ultraviolet ray glass as binder. A mixture of one part of adsorbent, one to four parts of finely powdered ultraviolet ray glass and one to five percents of fluorescent indicator was suspended in organic solvents as described earlier. The slurry was spread on soda-lime glass plate and air-dried. The thin-layer was heated in an electric furnace at 450°C to 750°C for several minutes to give an adsorbentfused glass layer.
The stability against a high temperature of the fluorescent indicators was shown by the following facts: the specific surface area, specific surface area diameter, particle density and median diameter were not changed by the welding process; no sintering of fluorescent indicators occurred; the scanning electron microscopic pattern was stable even after exposure to a higher temperature; no shift of peaks in the fluorescent spectra and no decrease in the intensity were observed; neither thermal mass change nor transition was observed under the welding condition.
These fluorescent sintered plates were applied to the thin-layer chromatographic separation of various organic compounds having absorption in the ultraviolet region: barbiturates, catechol amines, cephalosporins, local anaesthetics, steroids and water-soluble vitamines were separated on the silica gel sintered plates; cardiac genins and alkaloids, on the alumina sintered plates; and polychlorinated biphenyls (PCB) and chlorinated pesticides, on the Kieselguhr and silica gel sintered plates. The limits of detection of the visible quenching spots of these compounds on the fluorescent sintered plates were equal to those for the commercial precoated plates such as Merck's fluorescent plates. When a soda-lime glass was used instead of the ultraviolet rays glass as the binder the sensitivity were greatly reduced due to its absorption at wavelengths shorter than 300 nm.

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The precision of the determination of nanogram quantities of europium was increased greatly through the gravimetric sampling of standard and sample solutions. About 3 mg(≈0.003 ml) of europium solutions (1100 μg-Eu/ml) was weighed out by means of a polyethylene pycnometer (Fig. 1) and spottes on a piese of filter paper (0.5 cm in diameter). The filter paper was dried at room temperature and sealed in a polyethylene pouch.
The sample was irradiated, together with a standard in a pneumatic tube of JRR-2 at a neutron flux of 7.0×10¹³ neutron·cm^-2·sec^-1 for 1 minute. ¹⁵¹Eu (natural abundance 47.77%) is nuclearly trasformed through ¹⁵¹Eu(n, γ) ^152mEu to ¹⁵²Eu, which decays as
^152mEu β^-, γ(0.842 MeV, 0.961 MeV)→T_1/2:9.2h
¹⁵²Eu β^-, γ→T_1/2:12.7 years ¹⁵²Gd
The radioactivity of ^152mEu was measured by a high resolution Ge(Li)-detector and 1024 channel pulse height analyzer.
The repeatability precision of the method was 0.418% in terms of coefficient of variation for 4ng of europium, this value being higher than theoretical precision calculated from statistical fluctuation. The corresponding values were 2.3% and 5.20%, when a 1-ml pipette and a 10-μl microsyringe were used, respectively, for the sampling. The adoption of the gravimetric sampling and activation γ-ray spectrometry allowed the determination of nanogram quantities of europium with an error of 0.5% or less.
The procedure was applied to the test of local distribution of europium in red phosphors (europiumdoped yttrium oxide).
About 0.5 mg of the sample powder was weighed by a semi-micro balance, transfered to the weighed "weighing vial", then dissolved in 5 ml of 2 M HNO₃, and the weight of the solution was determined.
About 1 ml of the solution was introduced into a pycnometer, and europium was determined according to the above-described procedure. This experiment revealed that the doped europium was not uniformly distributed in commercial red phosphors from a microscopic point of view.

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Potentiometric redox titration of arsenic(III) in an aqueous solution of hydrochloric acid was studied by the use of a standard potassium iodate solution. The titration curve showed two steps, the first one corresponded to the reaction 5As³⁺+2I⁵⁺→5As⁵⁺+2I⁰ and the second to the reaction 2As³⁺+I⁵⁺→2As⁵⁺+I⁺ or 4I⁰+I⁵⁺→5I⁺. With an increase in the concentration of hydrochloric acid the redox potential in the first stage became higher and the first inflection on the curve was diminished but the second inflection became obvious especially in 36 M acid. On the contrary, with a decrease of the concentration the first inflection became sharp especially in 0.151.5M acid but the second became flat. (Fig. 1) Arsenic could be determined accurately by using one of the two inflections in appropriate concentration of the acid. The reproducibilities were higher than 99.8% for 0.0010.1 M solution of arsenic trioxide. The optimum conditions for the titration were as follows: concentration of hydrochloric acid, 0.151.5M for the first inflection and 35 M for the second inflection; temperature of the solution, 5°C; titration rate at the end point, 0.4 ml per minute.

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For rapid and sensitive determination of sulfur dioxide by means of its u.v. absorption, the use of long absorption cells of 50, 100 and 150 cm lengths is recommended. A Hitachi 207 atomic absorption spectrophotometer was modified to accommodate those long absorption cells. The standard gas from the gas cylinder was diluted properly with nitrogen, and was introduced into the absorption cell. Nitrogen is used also as the reference gas. At 207 nm the absorption is linearly proportional to the concentration of sulfur dioxide in the range from 0.2 ppm to 15 ppm almost independently of the flow rate of sample gas through the absorption cell. The detection limit of this method is 0.2 ppm. Vapors of several organic solvents and nitrogen dioxide interfere with the absorption at 207 nm.
A small portion of sample gas was injected into a tube connected to the absorption cell and was passed through the absorption cell with carrier nitrogen. By this procedure, 4×10^-9 mol of pure sulfur dioxide gives 1% absorption.
The Mg 2025 Å line emitted from magnesium hollow cathode lamp may also be used as the light source for this purpose.

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The extraction of uranyl ion from molten sodiumpotassium thiocyanate eutectic into the ο-terphenyl melt of tri-n-octylphosphine oxide (TOPO) was carried out under the dry atmosphere at 150°C. The transfer of uranyl ion from the molten salt solution into the organic solution was not observed in the absence of TOPO, but largely increased with an increase in TOPO concentration.
The variation of the distribution ratio with changes in TOPO concentration and in temperature indicated that the molar ratio of uranyl ion to TOPO was 1:2 and the change in enthalpy of about -5.5 kcal/mol.

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[in Japanese]

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