Takejiro Ozawa

Spectrophotometric determination of micro amounts of mercury, cadmium, and zinc by stepwise extraction with tribenzylamine

Abstract A rapid spectrophotometric method has been developed for the stepwise determination for mercury, cadmium, and zinc in mixtures. Optimal conditions have been established for the extraction efficiency of cadmium and mercury with a chloroform solution of tribenzylamine pre-equilibrated with hydrobromic acid. After addition of dithizone solution to the organic layers the absorbance at 490 nm or 510 nm is measured for mercury or cadmium, respectively. Even when the ratio of mercury, cadmium, and zinc is 10 -1 : 1 : 10 -5 , the metals can be determined successively.

Temporal variations in the constituents of volcanic ash and adherent water-soluble components in the Unzen Fugendake eruption during 1990-1991

A change in the chemical compositions of volcanic gases is one of the noticeable phenomena that frequently occurs prior to an eruption. Analysis of the water-soluble components adhering to volcanic ash is available for remote monitoring of volcanic gases from inaccessible volcanoes. It is a secure method for monitoring volcanic activity without using particular devices. Prolonged volcanic eruption at the Unzen Fugendake volcano from 1990 to 1995 started with a phreatic eruption after 198 years of dormancy. Volcanic activity changed from a phreatic and phreatomagmatic eruption to a magmatic eruption with pyroclastic flows in May 1991. The relationship between the chemical composition of volcanic ash and the contents of the water-soluble components adhering to it are discussed in relation to the early stage of the long-term eruption. Volcanic ash ejected by phreatic and phreatomagmatic eruption before dome formation was the product of the alteration in the volcanoclastic materials beneath the surface. The ash had a high content of water-soluble components, which was caused by the absorption of hydrogen chloride and sulfur dioxide gases from magma into wet debris before dome formation. Volcanic ashes which were generated by pyroclastic flows after dome formation were fresh lava fragments. While the contents of water-soluble sulfate adhering to the ash noticeably decreased, those of water-soluble chloride adhering to the ash hardly decreased. The considerable decrease in the contents of water-soluble sulfate was caused by the reaction of volcanic gases with dry lava fragments. Contrary to this, the concentration of hydrogen chloride gas in ash clouds was extremely high, which obstructed the decrease in the water-soluble chloride content in the ash. Volatility of chlorine and sulfur from volcanic rock suggests that the inner temperature of pyroclastic flows was higher than 600∼700°C at least.

Nature of volcanic gases and volcanic eruption

4. Conclusion1) The chemical composition of volcanic gases emitted from fumaroles and hot springs represents their stages of the differentiation of magmatic emanation at their effusing points, although the nature of volcanic gases varies with their orifice temperatures and geological environments. Consequently, changes of the chemical composition of volcanic gases indicate the variations in volcanic activities or geological environments.As we have seen in Table 1, halogen compounds and sulfur dioxide represent the earlier stage of the differentiation of magmatic emanation. Then the ratios such as F/CO2, Cl/CO2, Cl/SO2, SO2/CO2, SO2/H2S, H2S/CO2 and CO2/N2 may be used for the detection of the leakage of magmatic emanation depending on their stage of the differentiation of magmatic emanation and their geological environments. Laboratory experiment on heat treatment of igneous rocks supported the tendency of differentiation of volcanic gases obtained from the observation of natural volcanic gases.2) Periodic variations of discharges, temperatures, and chemical compositions of volcanic gases from geysers have been fully observed over the total eruption period of geyser action. By these studies and model experiments, the time and nature of eruptions of geysers could be satisfactorily predicted.3) Radioactivity of the volcanic gases and Tn/Rn can also be used effectively for this purpose, particularly this ratio of two isotopes is very useful for the study of transportation phenomena because the half-lives of each isotope are quite different from each other.

Differentiation of volcanic emanation around the boiling point of water in geothermal regions in Japan

ConclusionThe nature of the differentiation of the volcanic emanations around the boiling point of water has been made clear in detail by this study in some geothermal regions./The chemical composition of the parent volcanic emanation supplied at the Atosanupuri-Kawayu geothermal district has been calculated by the theory of the differentiation of the magmatic emanation proposed by the present authors. The chemical composition of the parent volcanic emanation obtained is not so different from that of the volcanic emanation observed usually at the active volcanoes. The facts observed at these geothermal districts support one of the process of the differentiation of the magmatic emanation, that is, the elimination of hydrogen chloride and sulfur dioxide from volcanic gases and the formation of acidic hot springs around the boiling point of water. Hydrogen chloride and sulfur dioxide supplied in deep places are usually eliminated from the volcanic emanation on the way up to the ground surface by the above mentioned processes of differentiation of the magmatic emanation and are not observed in fumarolic gases of low temperatures in such geothermal districts. When the drilling holes have enough depths to collect directly the parent volcanic emanations, hydrogen chloride and sulfur dioxide can be detected in their volcanic emanations. The volcanic gases from drilling holes at the Oowakidani geothermal district are the case which clearly demonstrates such situations.

The difference in chemical composition of the 1962 lava from miyakezima magma reservoir in Japan

Many examples of mixed magmas in banded lavas have been studied. Another type of mixed magmas or inhomogeneity of magma reservoir found in the 1962 lava flows of Miyake-zima Volcano erupted from fissures is reported.

Differentation of magmatic emanation

Chemical properties of magmatic emanation can be estimated roughly by i) volatiles from rocks by heating at various temperatures, ii) volcanic emanations, iii) residual magmatic emanations, iv) calculation from chemical equilibrium between volatile matters and magmas. Magmatic emanation is assumed to consist all of the volatile matters in magmas such asH2O, HCl, HF, SO2H2S, H2,CO 2,N2 and others (halides, etc.) at about 1200°C, although various kinds of magmatic emanations can be formed at different conditions. Magmatic emanation separated from magmas will change their chemical properties by many factors such as changes of temperature and pressure (displacement of chemical equilibrium), and reactions with other substances and it will differentiate into volcanic gases, volcanic waters, volcanic sublimates, and hydrothermal deposits (hot spring deposits).At temperatures above the critical point of water, separation of solid phase (sublimates), liquid phase, and displacement of chemical equilibrium may take place, and gaseous phase will gradually change their chemical properties as will be seen at many fumaroles. Chloride, hydrogen, andSO2 contents will gradually decrease along with lowering temperature.Once aqueous liquid phase appears below the critical point of water, all the soluble materials may dissolve into this hydrothermal solution. Consequently, the gaseous phase at this stage must have usually a little hydrogen chloride as is observed at many fumaroles. Aqueous solutions must be of acidic nature by dissolution of acid forming components, and by hydrolysis (Chloride type). When a self-reduction-oxidation reaction of sulfurous acid takes place, an aqueous solution of sulfate type will be formed. At this stage, solid phases consist of the remained sublimates which are difficultly soluble in aqueous solution, and deposits formed by reaction in the hydrothermal solutions.The gaseous phases below the boiling point of water, have usually a little water, and consist mainly ofCO2 type,H2S type,N2 type, and mixed type owing to elimination or addition of components by reactions with waters or wall rocks according to their geological conditions. Aqueous solutions which was of acidic nature must be changed into alkaline solutions by reaction with wall rocks for a long time. When the oxidation of sulfur compounds takes place, an aqueous solution of sulfate type will be formed. Hydrogen sulfide type of water will be formed by reaction of sulfides with acid waters or absorption of hydrogen sulfide. Carbonate type of water will be formed whenCO2 is absorbed. Solid phases at this stage consist usually of hydrothermal deposits except for that at solfatara or mofette.The course of differentiation of magmatic emanation could take place in more complicated ways than that of magmatic differentiation.

Solvent extraction of microgram amounts of magnesium with 8-quinolinol and tetrabutyl-ammonium iodide followed by spectrophotometry with chlorophosphonazo-III

Abstract A rapid and sensitive solvent-extraction procedure for the separation of magnesium is reported. Microgram (0.1–10) amounts of magnesium are extracted with a chloroform solution of 8-quinolinol and tetrabutylammonium iodide in the presence of tartrate and phosphate. Magnesium is then back-extracted into an aqueous buffer solution (pH 7.3; tetrabutylammonium hydroxide—boric acid) and determined spectrophotometrically using chlorophosphonazo-III. Up to 500 mg of sulphate, phosphate or cyanide, 200 mg of chloride, 20 mg of aluminum, barium or silicate, and 2 mg of calcium can be tolerated.

Forecast of volcanic eruptions by chemical methods

From the magmatic emanations differentiation point of view it is possible to calculate some ratios such as F/CO2, Cl/CO2, SO2/CO2, SO2/H2S, H2S/CO2 and CO2/N2 in the tumarolic gases for the forecasting of volcanic activity. In order to predict the cruptions of a volcano it is needed to select several fumaroles or hot springs having different regimes of variation of the above ratios. The study of some fumaroles composition at the Asama. Mihara, Kirishima and other volcanoes in Japan showed a close connection between volcanic gas compositions and state of the volcanoes.

Cu contents of volcanic rocks from Aso central cones

The Cu contents of twenty five representative rock samples from the central cones of Aso volcano have been determined by the Sandells colorimetric method. They range from 0.001 to 0.015 per cent and generally tend to be higher in basic rocks and lower in acidic ones. It has been also noticed that the rock types produced by fractional crystallization of high-alumina basalt magma have higher Cu contents, while those formed by contamination have lower.