The variation of fluorescence efficiency with concentration for the 2, 5-diphenyloxazole (DPO) and for the carbon tetrachloride in the toluene was studied under the aerated condition. The ratio of the light yield in absence of the quencher, I0, to that in its presence, IQ, at fixed solute concentration and at fixed irradiation intensity for direct excitation of the solute by 302 mμ UV was found to follow the relationshipI0/IQ= (1+K2 [Q] ), where (Q) is the quencher concentration andK2the quenching constant by CCl4relating to the DPO (Fig. 2) ; theK2value obtained was 6 liters/mole. Under indirect excitation of DPO via primary excitaion of the toluene by 260 mμ UV, theI0/IQvs. [Q] curve was found to be described by the Stern-Volmer relationshipI0/IQ= (1+K1 [Q] ) (1+K2 [Q] ), whereK1is the que nching constant relating to the solvent as shown in Fig. 2. Author obtained thefollowing values for zero concentration of DPO; K1=640 liters/mole andkq=2.5×1010 liters/mole. sec, wherekqis the specific rate of quenching calculated from the relation kq=K1/τ', τ' being the decay time of the fluorescence in the quencher free toluene solution. The specific rate, ktof excitation transfer from toluene molecules to DPO molecules was determined from the observed relationship between fluorescence efficiency and DPO concentration and combined with other relevant data reported by other authors; kt=8.56×1010 liters/mole⋅sec. The theoretical curves of the fluorescence efficiency vs. DPO concentration based on the energy-exchange processes given in Table 1 and the experimental values of rate constants mentioned above were found to fit satisfactorily the experimental values of fluoresence except the low concentration range (Fig. 6) . The disagreement seems to be explained by the assumption that the solvent emission is absorbed by the solute molecules, giving solute fluorescence with quantum efficiency of about unity. The validity of the assumption should, however, be checked experimentally. The quenching constantK1under60Co-γ ray excitation was larger by the factor of 2.2 than that under 260 mμ UV excitation. Similar experiments, although not so extensive as the case of DPO mentioned above, were carried out for p-terphenyl and their results have been also presented in the text.
According to the standard method, the co-precipitation with ferric hydroxide with ammonia water (pK 4.72) was utilized for the separation of140La from a mixture of140Ba-140La. Almost all140Ba in the case without carriers and about 7 % of140Ba in the case with carriers were co-precipitated with ferric hydroxide. Therefore, the high purity of140La could not be obtained by this method. To separate pure140La from a140Ba-140La mixture, several organic bases such as pyridine (pK 8.77), α-picoline (pK 7.52), benzylamine (pK 4.63), n-butylamine (pK 3.39) and ethylenediamine (pK 4.07) were also used as precipitants. By using these organic bases, it was possible to maintain a pH value of a test solution within a narrow range easily. When pyridine was used instead of ammonia water, only 0.04-0.2% of140Ba was co-precipitated without carriers. And, by α-picoline only 0.1-0.8% of140Ba was co-precipitated. When benzylamine wsa used as a precipitant, the purity of140La was nearly equal to the case of ammonia water. The contamination of140Ba is inversely related to the degree of the pK value of the precipitants, that is the quantity of140Ba co-precipitated with ferric hydroxide increases in the concentration of OH-ion in the solution. Although a similar result was obtained in the case of90Sr-90Y, the purity of140La is lower than that of90Y. This may be because Ba2+has a greater affinity for Fe (OH) 3than Sr2+.
A study is described for the separation and concentration of various metals from an aqueous solution by carrier precipitation with copper sulfide using radioisotope as a tracer. One milligram of copper (II) and 0.06-0.1 mlof 1 Msodium sulfide solution are added to 20-50 mlof solution containing μg quantities of metals, and the distribution of μg amounts of metal is investigated by measuring the radioactivity in liquid phase or solid phase (precipitate) . Gold, silver, mercury, platinum and copper are collected completely from 0.1-1.0 N hydrochloric acid solution, whereas cobalt, thallium and zinc are retained in solution. The increase of pH above 9.0, however, enhances the recovery of cobalt and zinc up to>90%. The recovery is not affected by the difference of carrier or the method or rate of precipitation. Though the presence of chloride ion (<25%) does not decrease the recovery, the presence of complexing reagents of trace metals diminishes the recovery remarkably. The treatment of copper sulfide precipitates is demonstrated by several methods. This procedure has effectively been applied to the separation and concentration of traces of gold, silver or mercury in copper, lead, zinc, nickel and manganese.
Neutron absorptiometry for analysing of boron contents in borosilicate glass and frit was investigated. A Ra+Be of 4.81 mg Ra fast neutron source and the paraffin were used to slow down the fast neutrons to thermal velosity. The neutron detector was a ZnS (Ag) -B polyester scintillator of 2 inches diameter and 5/8 in thickness. The relations between the intensity of slow neutrons produced and the size of paraffin were studied, and then a neutron howitzer suitable for neutron absorption analysis was prepared. The measurements of neutron transmittanee of borosilicate glasses and frits of known boron contents were performed. The accuracy of boron determination is highest in the case of σnx=2, where σ is cross section per atom, n is the number of atoms in cm3, and x is the thickness of sample material to be tested. The relative error of boron determination was estimated as about ±9% in 10 minutes counting for a sample when B2O3content was 5% for frit sample of 1.75 g/cm2thickness.
This paper describes the variation of gamma ray distribution and the average gamma energy of fallout due to nuclear detonation from September 1961 until September 1964. Fallout samples were collected with continuous dust-samplers. The gamma ray spectra of the samples were measured by a 400-channel gamma ray spectrometer. The detecter was used the sodium iodide crystal 5inφ×4 in and it was set in the ion box about 20 cm thick. Analysis of the gamma ray spectra were made by using the strip-off method. The energy ratio to the total gamma activities in the fallout was calculated from the net count-rate of the photo-peak. The ratio of gamma energy (0.76 MeV) from95Zr-95Nb ranged from 50 percent to 88 percent in the period, The average gamma energy of the Fallout in the operiod was nearly constant. The average value was 0.68 MeV.
From the standpoint o f radioactive decontamination, the adsorptive properties of several kinds of sand and clay, occurring in various parts of Japan, were investigated by batch method using fission product as an adsorpate. The percent removal was different from sample to sample and ranged between 40-100%. The relation between the removal of fission products and chemical composition was not clear. As to mineral composition, it was observed that all the samples rich in calcite adsorbed effectively and resembled each other in their adsorptive properties. The percent removal for rare earthes was high, while that for ruthenium was low. In the case of strontium and cesium, decontamination was greatly affected with the nature of materials but there was little difference in the pH dependence between strontium and cesium regardless of materials.
Recently some photoscans are considered to have more clinical values than other monotone-dot scans. But it needs a special tube whose brightness must vary related with the density of pulses (these linearly related with distribution of radioactivity) and some complicated circuits to represent the results. In this paper, a very simple way to get photoscintigrams is reported. This apparatus is superior also in the point of economy. For this purpose, the brightness of the lamp (argon lamp) is decreased by an absorption filter made of a plastic plate until the film density developed can not be observed by one pulse or by an accumulation of a few pulses. By this way the density of the film can be observed when the accumulation of pulses becomes more times, and then the density of the film increases by the number of the pulses accumulated, according to the density characteristic curve of the film. Consequently the density in scintigrams is varied consecutively according to the exposed number of pulses accumulated, that is related with an activity of radioisotope distributed in a patient. To make more suitable scintigrams the shape of the light dot is widened, and the brightness of the light is controlled by a variable resistance inserted in the circuit of argone lamp directly. And the results by this scanner about the phantom o f thyroid and liver are compared with results by other scanners, and the scintigrams by this apparatus is considered to be rather superior than by others instead of the smaller crystal of this apparatus. Some considerations in future are added.