Iron (III) reacts with CAS to form a water-soluble blue complex with highest and fixed absorbance at 575 mμ by adjusting pH 4.8 to 5.7 after the addition of CAS. The molar extinction coefficient 4.15×10⁴enabled CAS to be used for the determination of iron (III). The authors thus proposed the following procedure.
Dilute the weakly acidic solution containing as little as 3.4 to 70 μg of iron(III) to 30 ml with water. Add 0.6 ml of 0.275% CAS solution and adjust the pH to 5.3 with 0.25M sodium acetate solution. Dilute the solution to 50 ml with water and measure the absorbance of the colored solution at 575 mμ against the reagent blank.
Aluminum, gallium, tin(IV), copper, phosphate, oxalate, citrate, EDTA and NTA interfered.
It was found that the mole ratio of iron(III)-CAS in the complex were 1 : 2 and 2 : 1 in sodium acetate buffer or 1 : 1 and 4 : 1 in ammonia buffer, respectively.

View full abstract

It is well known that sulfides interfere with the photometric determination of phenols in water by the 4-aminoantipyrine method. The present work shows that this interference is suppressed by the addition of Triton X-100 even if a large amount of sulfides (about 80 ppm as sodium salt) is present. Triton X-100 is reasonably assumed to serve as a protective colloid for sulfur resulting from the oxidation of sulfides by potassium ferricyanide, which is one of the color-developing reagents in the 4-aminoantipyrine method. When sulfides are present in a concentration smaller than 20 ppm, it was not necessary to add Triton X-100 but only to increase the adding amount of potassium ferricyanide. The proposed method has a great advantage in that the tedious procedure such as distillation for separating sulfides is eliminated. Continuous determinations under the addition of Triton X-100 were carried out with a good transient response and with a lower limit of determination 0.2 ppm for phenol.

View full abstract

A flame spectrophotometric method was described for the determination of rubidium in sea water. The measurement of emission intensity of rubidium was made at the wavelength 794 mμ with Shimadzu spectrophotometer model QV-50 (photomultipleir R-136).
In order to prevent the interfering effect of diverse ions, rubidium in sea water was concentrated by coprecipitation with potassium tetraphenylborate, and the precipitates were converted into chlorides. Rubidium chloride was separated from potassium chloride by utilizing the difference of solubilities in hydrochloric acid-ethanol solution, whereby 93% recovery of rubidium from sea water was ascertained by using ⁸⁶Rb as a tracer. Rubidium in several sea water samples was estimated to be 0.140.17 mg/l.

View full abstract

By using a difference in behaviours of ammonium salts and potassium salts in mixed solvents of wateralcohols or water-acetone, an alkalimetric titration of ammonium salts with aqueous potassium hydroxide solution as the titrant was presented.
The apparent pH value of an aqueous solution of a salt was increased by mixing organic solvents, among which acetone was most effective. Comparing potassium salt and ammonium salt, the former was much influenced in increasing pH.
The titration of ammonium salts was done in solutions containing about 60% (v/v) of acetone, and titration curves very similar to ordinary weak acid-strong base titration curves were obtained.
A mixed indicator of phenolphthalein and bromophenol blue was useful. The concentration of free acid in an ammonium salt solution was also determined by an inspection of the titration curve.

View full abstract

The addition method (Fig. 1) previously reported, which is applicable to the concentrated solution, has been applied to the determination of rare-earth elements. The measurements were done separately on two classified groups, i. e. cerium-group elements and yttriumgroup elements. As the analytical lines were selected K lines for the former (Fig. 2) and L lines for the latter, respectively, taking into consideration their mode of overlapping. Respective lines are given in Table II. Studies were made to the treatment of higher background values for K series (Fig. 3) and also to the correction for some overlappings of L series spectra (Fig. 4).
The analysis of synthetic samples by this method gave values with less than 5% of relative errors in the presence of diverse elements (Table III).

View full abstract

The extractive ion-exchanges between nitrate ion and halide ions with a high molecular weight amine have been discussed by the modified Argersinger's theory for the equilibrium of ion-exchange, by which the ion-exchange equilibrium constants independent of the concentration of the aqueous phase can be evaluated. The activity coefficients in the organic phase are near to unity for the tri-n-octylammonium salts of those acids, probably indicating that the tri-n-octylammonium ion and anions combine to form neutral ion pairs. At the extraction processes of inorganic acid with high molecular weight amine, the free energy change associated to the hydration-dehydration of the anions in exchange process is proved to be more significant than electrostatic free energy change for exchange of anions in the organic phase.

View full abstract

Decimilligram determination of organic nitrogen based upon the sealed tube combusition and the measurement of expanded volume of nitrogen over 50% KOH solution has been improved with a modified apparatus and especially with a revised method of calculation.
The main revisions are the correction of volume of water replaced with expanded nitrogen in the combustion tube for the formation of a reversed meniscus at the end point of titration and the correction for the capillary rise of 50% KOH solution in the combustion tube and also for the film of 50% KOH solution on inside wall of the combustion tube.
A series of analytical data for several standard substances indicates mean error within ±0.03% and standard deviation within ± 0.05%. In case of nitrogen content less than 20%, the standard deviation of ±0.03 % has been attained.

View full abstract

Back-extraction of iron(III) from the methyl iso-butyl ketone extract of tetrachloroferrate(III) was attempted by putting silica gel into the organic solution, whereby silica gel of thin-layer chromatographic use was employed under the conditions that it contained certain amounts of water, i. e., (i) 42.09, (ii) 38.52, (iii) 24.46, (iv) 3.34 and (v) 3.11%, respectively. About 0.25 to 3.0 g of each silica gel was put into a 50 ml glass-stoppered centrifugal tube, and 10 mlof methyl iso-butyl ketone solution of tetrachloroferrate(III) was added. The organic solvent solution contained 2.683 μg Fe/ml and was saturated with 6 N hydrochloric acid, since it had been obtained after the liquid-liquid extraction of iron(III) chloride in 6 N hydrochloric acid with the same organic solvent. The mixture was shaken and centrifuged. The supernatant of the upper layer was submitted to the spectrophotometric measurement of iron(III). The amount of iron(III) remaining in the organic solvent was determined by taking into account of the volume change and the percent elimination was calculated in each case. It was found that the more the amount of water in silica gel was, the greater the elimination of iron(III) from the organic solvent. It indicated that the back-extraction of iron(III) was achieved simply by water in fine pores of silica gel. This technique seems to offer a convenient method for treatment of organic solvents after the extraction.

View full abstract

More than ten sorts of metal chelates of hexafluoroacetylacetone were synthesized, and the gas-chromatographic separation of their mixtures was attempted. Well-defined chromatograms were obtained by increasing the rate of the stationary liquid to the support to 510%, 10 times as much as that previously employed by the authors for the separation of organometallic compounds. Separation of hexafluoroacetylacetonates of beryllium (II), aluminum(III), chromium (III), gallium(III), iron(III) and rhodium(III) from their mixture was successfully done with symmetric chromatograms at 60°C of column temperature.
With the column using Fluorolube HG-1200 as the stationary liquid, employed newly in this experiment, the ordinary order of elution of beryllium(II) and aluminum(III) were reversed, whereby aluminum was eluted out at first and then beryllium without a overlapping of their peaks. On the other hand, the optimum column temperature for the separation of mixed samples involving copper(II)-hexafluoroacetylacetonate was 90°C, whereby satisfactory results were obtained for the separations of iron(III) and copper(II) and of rhodium(III) and copper(II).

View full abstract

A method for the chromatographic separation of organic or inorganic mercuric compounds was studied on anion-exchange paper, Amberlite SB-2 (R-Cl). The sample solution was spotted on a strip (0.5 × 20 cm) of the paper at a point of 2 cm from the end. After drying in the air, it was developed ascendingly in a jar using 1.6 N nitric acid as the mobile solvent for 1 hour. After drying and spraying with dithizonechloroform solution, the R_f was estimated. R_f values were: for alkyl mercuric compounds 0.190.33, inorganic mercuric compounds 0.090.11, and phenyl mercuric compounds 0.010.03. The limit of identification of mercury by this method was about 0.2 μg. Other metals interfered scarcely.
An investigation was further performed on the determination of inorganic mercuric compounds by measuring the area of the colored zone on strips of Amberlite SB-2 (R-Cl), and the amount, 14 mg, of mercury was found to be proportional to the colored area at pH 5.0.

View full abstract

Micro amounts of impurities in silicon carbide, the raw materials of varistor, were colorimetrically determined. Iron, mixed up during the crushing process, was completely dissolved in hydrochloric acid, and determined by measuring the absorbance of its thiocyanate complex at 480 mμ. The fading rate of this complex was so high that a small amount of ammonium persulfate had to be added to the solution.
Then, the sample was fused with the mixture of sodium hydroxide and potassium nitrate, and treated with hydrochloric acid to separate silica from the impurities. After filtering, iron and aluminum were extracted with chloroform as their oxine salts from neutral solution, and simulatneous determination of them was performed by dissolving two equations obtained from the measured absorbances of the extracted solutions at 390 and 470 mμ. Reagent blank carried through the entire procedure was used as the reference.
Total amounts of alkaline earth metals were determined by measuring the absorbance at 610 mμ of their chelates with thymol phthalein complexone formed by adjusting the pH of above filtrate to 11.5.
Satisfactory results were obtained by applying this method to the analysis of NBS standard samples.

View full abstract

For the analysis of microamounts of impurities iniron, the extraction behavior of thirty-one elements (5 μg each) in the presence of 100mg iron with methyl isobutyl ketone was studied by use of radioisotopes.
As a result, the extraction abilities of the elements extracted from 7.5 N hydrochloric acid solutions into methyl isobutyl ketone have been found as follows:
As(V) 16%, Au(III) 100%, Ba(II) 0%, Bi(III)0%, Co(II) 1%, Cr(III) 1%, Cu(II) 4%, Fe(III) 100%, . Ga(III) 100%, Ge(IV) 93%, Hf (IV) 9%, In(III) 67%, K(I)8%, La(III) 0%, Mn(II) 0%, Mo(IV) 92%, Na(I) 1%, Nd(III) 0%, Ni(II) 0%, Pb(II) 5%, Pr(III)0%, Pt(IV) 74%, Re (VII) 73%, Sb(V) 100%, Sc(III)0%, Se(IV) 39%, Sn(IV) 63%, Ta(III) 0%, Te (IV) 75%, W (IV) 61% and Zn (II) 10%.

View full abstract

Chromatograms were developed in 3 to 4 hours by an ascending technique with a solvent mixture of n-butyl alcohol-acetic acid-water (4:1:1, v/v). Chromatograms developed were dried and sprayed with the reagent of following compositions: 1% aqueous solution of Mohr's salt, 10% aqueous solutions of NH₂OH·HCl and pyridine (20:2:1, v/v) for the identification of pyridinecarboxylic acid whose carboxylic group being located at the α-position and then sprayed with a 2% alcoholic solution of 2, 4-dinitrofluorobenzene for the detection of nicotinic acid and isonicotinic acid. The identification limit was found to be 2 μg of picolic acid and nicotinic acid, and 4 to 6 μg for other pyridinecarboxylic acids. R_f values of pyridinecarboxylic acids obtained are in the following order: pyridinemonocarboxylic acids>pyridinedicarboxylic acids>pyridinetricarboxylic acids.

View full abstract

Since a greater part of ⁵¹Cr discharged into the sea is considered to be present mainly in the valence state of VI, it was reduced to Cr(III) by iron(II) and collected by the ferric hydroxide coprecipitation method. The carrier of chromium (0.09 mg) was added to 50 ml of sea-water containing tracer ⁵¹Cr and the pH of the mixture was brought to 1.8 by the addition of hydrochloric acid. A solution of iron(II) sulfate (0.6 mg Fe) was added to reduced Cr(VI) and then the mixture was adjusted its pH at 8 to precipitate hydroxides with sodium hydroxide after the addition of 2.25 mg of iron(III) as a collector. ⁵¹Cr was collected rapidly and quantitatively as hydroxide. The procedure has been also proved to be satisfactory in a larger scale operation (80 fold). Several other radioisotopes such as ⁵⁴Mn, ⁵⁹Fe, ⁶⁰Co and ⁶⁵Zn were also coprecipitated quantitatively and it was found to be advantageous in the separation of chromium from the hydroxides precipitates that the reducing agent and the collecting agent are the same, material, iron.

View full abstract

Minor amounts (0.02 to 0.6%) of rare earth elements (Y, Er, Ho, Gd, Eu and Sm) in dysprosium oxide with high purity were determined by fluorescent X-ray procedure. Samples and standards were prepared by briquetting the oxide powder. Probable errors at a concentration of 0.05% level estimated by a statistical method were 4% (for Y) to 17% (for Sm) for each element. Detection limits of rare earth oxides in dysprosium oxide ranged from 0.005% (for Y) to 0.02% (for Sm).

View full abstract