Small Amounts Of Impurities Research Articles

Spectrographic determination of small quantities of impurities in some final products of the over-all processing of nephelinic syenites. I

Spectrographic determination of small quantities of impurities in some final products of the over-all processing of nephelinic syenites. I

4B4 - Rate determining processes for the production of radiation in high power molecular lasers

The excitation mechanisms and relaxation processes will be described for a closed molecular gas laser of 240 cm length and 2.3 cm diameter filled with 1 torr carbon dioxide, 2.5 torr nitrogen, and 7.2 torr helium; the influence of adding 0.2 torr water vapor is discussed. When all the four components are present, an output of 103 watts is reached with an efficiency of 12.5 percent. It will be argued that in the absence of water vapor the deactivation of the lower laser level is rate determining for the radiation production. However, the addition of water vapor (0.2 torr) contributes greatly to depopulating the lower laser level by thermal relaxation, and it makes the output increase by more than a factor of two. In the latter case the vibrational excitation of the nitrogen molecules by electron impact is rate determining. We have observed that small amounts of impurities with partial pressures, sometimes less than 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> torr, may cause a considerable decrease of radiation output. This "poisoning" effect, caused by very small impurity concentrations, can be avoided by using a discharge tube made from fused silica (quartz).

Arsinic acids

The use of (diethylamino)dichloroarsine as a very useful intermediate in the preparation of C 5C 20 arsinic acids is described in this paper. This reagent, which contains only two chlorine atoms, reacts with the Grignard reagent with very small amounts of impurities being formed. The melting points of the arsinic acids exhibit alternation of the type observed in the fatty acids and the melting point appears to reach a convergence temperature. The differential thermal analysis curve exhibits an endothermic peak just prior to melting which is probably due to a crystalline phase transition.

Oxidation of cobalt at high temperatures

The kinetics and mechanism of oxidation of cobalt at 1000°C has been studied in the pressure range 0.01–0.65atm. It has been shown that oxidation proceeds according to a parabolic law, the growth of the scale occurring solely by the outward diffusion of the metal. The dependence of the reaction rate on the oxygen pressure can be described by the equation: K p = 1 ⋅ 45 × 10 − 7 p O 2 1/3⋅3 Employing the method proposed by K. Fueki and J. B. Wagner 20 the coefficients of self-diffusion of cobalt in cobaltous oxide have been calculated from the kinetic data for various values of the oxygen pressure. The results obtained are in good agreement with the values of the self-diffusion coefficients determined by Carter and Richardson 17 using the radioactive isotope Co 90. The dependence of the self-diffusion coefficients of cobalt in cobaltous oxide on the oxygen pressure is given by the equation: D C o = 2 ⋅ 9 × 10 − 9 p O 2 ′ 1/2⋅ 9 It has been observed that small amounts of impurities normally present in commercial cobalt play a decisive role in the mechanism of the oxidation. The scale growth in the latter case takes place via the two-directional diffusion of both reactants.

Raman spectra of cyclohexane crystal I and crystal II

The Raman spectra of the crystals I and II of cyclohexane have been studied. The crystal I, stable between the freezing point and 186°K, has been found to be most easily super-cooled under rapid cooling to 77°K when the sample has contained a small amount of impurity. The crystal II, stable below 186°K, has been obtained under rapid cooling of pure cyclohexane or through annealing of the supercooled crystal I over a wide range of temperature. The Raman spectrum of crystal I has exhibited splittings only for two bands 2890 and 2920 cm −1. The weak bands 1057 and 1421 cm −1 which appear only in the crystal have been assigned to the fundamentals of a 2 g species. The occurrence of a 2 g fundamentals has led to the space group of T h 2 for the structure of crystal I. A remarkable effect of temperature on the band widths of the degenerate fundamentals in crystal I has suggested the existence of considerable freedom for molecular rotation in the crystal lattice at high temperatures. The Raman spectrum of crystal II at 77°K is quite different from that of crystal I at the same temperature. It has been found that in crystal II each fundamental of e g species has split into two components, while all the fundamentals of a 1 g and a 2 g species have appeared as single bands. Possible assignments for the bands 2890 and 2920 cm −1 have been suggested on the basis of this rule.

Influence of Lead Impurity on the Low-Temperature Color-Center Production in KC1

The growth of optical absorption bands in the visible and ultraviolet as a function of 1.5-MeV electron irradiation at liquid-nitrogen temperature has been measured for high-purity and lead-doped KCl. Dissolved lead causes the coloration near 360 nm to be enhanced; the rate of growth increases monotonically with Pb concentration, in agreement with previous studies of trapped holes. The $F$ coloration is also enhanced by small amounts of impurity; however, the $F$-growth enhancement saturates at impurity levels of 20-100 ppm lead. An actual lowering of the $F$-center production rate is observed when samples doped with more than 100 ppm lead are used. This lowering is shown to be due to an increase in the $\ensuremath{\alpha}$-center-to-$F$-center ratio in highly doped KCl. An explanation is proposed for the increased $F$-center coloration in terms of interstitial-$F$-center recombination and interstitial stabilization by the impurities.

Magnetic properties of hematite single crystals

Abstract An experimental study of natural and synthetic single crystals of hematite containing small quantities of impurities was made to establish what effect impurities had on a variety of magnetic properties. In both types of crystals the average values for the weak magnetic moment were comparable regardless of the impurity. A triaxial anisotropy was observed in the basal plane of many natural crystals and for the samples with the largest anisotropy the major impurity was found to be Sn; this was also the only impurity which induced a triaxial anisotropy in the synthetic crystals. The coercive force was also much larger in the natural and synthetic crystals containing Sn. The transition temperature was found to be progressively lowered by increasing the amounts of certain impurities but the values for this temperature in synthetic and natural crystals containing the same impurities were often different. For the synthetic crystals, small additions of Sn depressed the transition temperature to a greater degree than an equivalent amount of any of the other impurities. In the region of the low temperature transition a large change in the value of differential susceptibility with temperatures was observed for both pure and impure crystals.

LOW-TEMPERATURE NEUTRON IRRADIATION DAMAGE IN ALUMINUM AND GOLD

Fast-neutron irradiation damage at 1.74 °K and its recovery to 100 °K have been investigated in Al and Au by means of residual electrical resistivity measurements. The effects of impurities, quenched-in vacancies, and dislocations were studied. It was found that the damage rate of Al was unchanged by impurity concentrations of less than 0.5 at. % and quenched-in vacancy concentrations of less than 0.002 at. %. Dislocation concentrations of ~2 × 1010/cm2 in Al and ~1011/cm2 in Au increased their damage rates by 35%and 50% respectively. Small amounts of impurity (~0.02 at. %) in Au increased its damage rate by 15% and suppressed the enhancement caused by deformation. The stage I recovery of Al and Au was only slightly increased by extra dislocations, but was increased considerably by quenched-in vacancies. An impurity concentration of ~0.5 at. % suppressed the stage I recovery of Al, but not that of Au. The results are interpreted in terms of channeling in Al and collision chains in Au.

Sintering-Cobalt – Chrome – Molybdenum Alloys for Osteosynthesis

OF the materials which have been used for surgical prosthetics, the stellite alloys (based roughly on 65 cobalt, 30 chromium, 5 molybdenum) have excellent strength and adequate corrosion resistance1. Unfortunately these alloys are available only in the form of castings which, in the absence of any special techniques, develop a very large grain-size in the material. Small surgical implants have cross-sectional areas comparable to this grain size which may result in their mechanical properties being dependent on the random crystal orientation of a single grain to an applied stress. The strength of the implant may also be limited by weakness of the grain boundaries in the material. Any small amounts of impurity will segregate to the grain boundaries of the casting; when the grain size is large, the grain boundary area becomes relatively small and so the impurities may reach a high concentration. It is thought that both the foregoing factors are responsible for the wide variation and unpredictability of mechanical tests carried out here2–4. Therefore, a refined grain structure of these alloys should have beneficial effects by (a) giving a truly polycrystalline material, preferably of higher purity, and (b) spreading any impurities more uniformly throughout the material by increasing the grain boundary area.

Recovery of quenched-in resistivity in doped gold

Changes in electrical resistivity of quenched gold wires, to which small amounts of silver, nickel, and antimony were added, have been studied in detail at annealing temperatures in the range (20÷170) ‡C. Some results with Ag-doped specimens were explained in a previous paper by assuming the formation of vacancy-impurity complexes whose binding energy is about 0.3 eV. The results with Ni-doped specimens are qualitatively similar but suggest a very small binding energy of the vacancy-Ni atom complex. Evidence of motion of defects is also obtained at low temperature. In the case of Sb-doped specimens different features are noticed, the deviations from the kinetics of vacancies in pure gold being more apparent for specimens containing small amounts of impurities than for more heavily doped specimens.

Pseudomonas aeruginosa proteinase

Abstract Extra-cellular proteinase of Pseudomonas aeruginosa IFO 3080 ★ has been obtained as needle-like crystals by the usual purification procedures, and some of its general properties have been examined. 1. 1. The proteinase after recrystallization three times, appears to be homogeneous on electrophoresis and ultracentrifugation; a small amount of impurity has been detected by column chromatography on DEAE-cellulose. 2. 2. The iso-electric point has been found to be at a pH slightly below 4.08. Maximum absorption of the ultraviolet spectrum is at 280 mμ and the minimum at 250 mμ. 3. 3. The proteinase is fairly stable over the pH range of 5 to 9 at 30°, and, in neutral solution, below 50°. 4. 4. The optimum pH for proteolytic activity is pH 7–9, and the optimum temperature is 60°. 5. 5. The proteinase acts on various protein substrates such as casein, gelatin, egg albumin and haemoglobin, but not on native collagen. Various synthetic substrates such as benzoyl- l -arginine amide, acetyl- l -tyrosine ethyl ester, carbobenzoxy- l -glutamyl- l -tyrosine, carbobenzoxyglycyl- l -phenylalanine and l -leucinamide are not hydrolysed. 6. 6. Reducing agents, -SH reagents, DFP and natural inhibitors from soy bean and potato do not affect the enzymic activity of the proteinase. Oxidizing agents inactivate the enzymic activity. Further, metal-complexing agents such as EDTA and o -phenanthroline inhibit the enzymic activity, although α , α ′-dipyridyl, NaF, citrate and oxalate do not affect it. Heavy-metal ions such as Ag + , Cu 2+ , Hg 2+ , Pb 2+ , Fe 2+ , etc., inactivate the enzymic activity. Inactivation is also seen with high concentrations of urea.

IONIZATION BY ALPHA PARTICLES IN BINARY GAS MIXTURES

The W value (average energy loss per ion pair) for alpha particles was measured in a number of binary gas mixtures of molecular gases as a function of the fractional pressures. The W of the mixture W/sub ij/) can be represented in terms of the W's of the pure constituent gases (W/sub i/, W/sub j/) and the fractional pressures (P/sub i/, P/sub j/) by the relation. W/sub ij/= (W/sub i/ - -W/ sub j/). Z/sub ij/ '' + W/sub j/, where Z/sub ij/'' = P/sub i//(P/sub i/ + f/ sub ij/P/sub j/), in which f/sub ij/ = constant determined empirically for each pair of gases. These constants very nearly satisfy the relationship f/sub ij/ == f/sub j//f/sub i/ = (f/sub j//f/sub k/)/(f/sub i//f/sub k/) = f/sub kj//f/sub ki / , where i, j, and k refer to any three gases. Thus, if the following f-values are assigned to the gases in this study (N/sub 2/, 1; CO/sub 2/, 1.8; H/sub 2/, 0.5; O/sub 2/ CH/sub 4/, 1.8; C/sub 2/H/sub 4/, 3.4; C./sub 2/H/sub 6/, 3.6; C/ sub 3/H/sub 6/, 4.5; C/sub 3/H/sub 8/, 4.5. C/sub 4/H/sub 8/, 6.3) then the constant f/sub ij/ determined from the ratio of any twomore » of these will serve to predict the W of any mixture of these two gases with an accuracy better than 1%. Slight departures from the W predicted by the above equation were noted in the case of nitrogen mixtures, indicative of an effect similar to that observed in the noble gases when small amounts of impurities are added. (auth)« less

Study on the recrystallization behavior of 99.999% super-purity aluminium

The recrystallization behavior of super-purity aluminium is much influenced by a small amount of impurities therein contained. According to Trillat, for example, 99.9986 percent purity aluminium starts to recrystallize slowly at 0°C, and is fully recrystallized when heated at 100°C for 6-10 minutes, while 99.997 percent purity metal does not ercrystallize even heated at 100°C for 6hrs.Meanwhile, one of the authors has found out that 99.996 percent purity metal begins to recrystallize in 40 days under room temperature and in 80 days under 0°C, while 99.994 percent or under metal does not recrystallize under room temperature even after 6 months.This is to report about the study on the recrystallization behavior of 99.999 purity metal which is produced by the three-layer electrolytic refining process.The findings are summed up as follows:(1) Self-annealing phenomenon in 99.999 percent metal takes place easily in the process of cold rolling. Under the cold rolling at 20°C, its recrystallization ratio, when the heavy reduction of 90% to 96.7% in given, reaches to 10% to 18%. The effect of reduction to this phenomenon is quite remarkable, but under the reduction of less than 75%, such self-annealing phenomenon is not observed.(2) The effect of reduction on the recrystallization temperature is also remarkable. The recrystallization temperature and activation energy sharply decrease as the reduction increases.(3) Recrystallization is observed in the metal, to which the heavy reduction of 96.7% is given, in two or three months under the temperature of 0°C. Meanwhile, under the room temperature, the metals, to which 96.7%, 90% and 75% reduction are given, shows the recrystallization area of about 70%, 50% and 2% respectively in 100 days. (Before aging, the area is 18%, 10% and 0% respectively) On the other hand, when the reduction is 60%, the recrystallization does not take place in the same period. But, by the aging at 58°C, the recrystallization area increases rapidly within 8 days as same as in the case of 100 day-aging at room temperature.

A New Picture of the Vibration of Linear Lattices

A new version of the method of transfer matrix is presented, which largely simplifies the derivation of eigenfrequency equation, on the one hand, and gives rise to a very simple and vivid picture (vector picture), on the other hand, of the normal vibration for the linear isotopic lattices. By using this version and the vector picture, the wave forms of the extra- and in-band vibrations of the lattices containing a small amount of impurity and the eigenfrequency spectrum of generalized diatomic lattices are discussed, obtaining some interesting conclusions.

Some Activation Analyses of Six Trace Elements in Marine Biological Ashes

SYSTEMATIC knowledge of the abundance of trace elements in marine organisms is far from complete. Most currently accepted values have been determined by spectroscopy or flame photometry but for a number of elements these methods leave much to be desired. The method of activation analysis not only increases the sensitivity for many trace elements1 but also eliminates the necessity for running ‘blank’ analyses on the reagents since small amounts of impurities contained in the reagents will not be measured.

Recrystallization of Zone-Refined Lead

THE decrease in recrystallization temperature with increasing purity of a metal is well known. This general phenomenon has been observed in the past few years especially in high-purity aluminium obtained by zone-refining; moreover, in France it has been demonstrated that recrystallization will occur at remarkably low temperatures. The work of Dimitrov and Albert1,2, is representative of the recent papers on this subject; they have shown that following 97 per cent deformation at low temperatures, the recrystallization of aluminium was complete after 200 hr. at −52° C., and at least initiated after 100 hr. at −79° C. These low-temperature investigations are significant because it seems that no current theory readily explains the processes involved. Then in conjunction with other experiments on zone-refined aluminium involving recrystallization and other phenomena, they show the marked effect of small amounts of impurity.

THE FORMATION OF GENTIOBIOSE AND OTHER SACCHARIDES DURING PRESSURE‐STEAM STERILIZATION OF A GLUCOSE‐SALTS SOLUTION OF pH 6.8

SUMMARY: Two samples of glucose of high quality were examined chromatographically for impurities in the form of saccharides other than glucose. One contained gentiobiose and at least three other sugars amounting to 35 mg/100 g of glucose; the other contained gentiobiose and at least four other sugars, the total quantity being 25 mg/100 g of glucose. Glucose from which these small quantities of impurities had been removed was employed, together with inorganic salts, to make up a medium suitable for the cultivation of moulds and the pH value was adjusted to 6·8. This medium was sterilized at 10 lb pressure for 15 min and it was afterwards found that a mixture of saccharides amounting to 125 mg/100 g of glucose had been formed, the principal constituent being gentiobiose; the remainder consisted of a monosaccharide and two oligosaccharides not yet identified. These sugars were not detected in similar glucose salts media which had not been heated but which had been sterilized by Seitz fitration.

Micellar dispersion of α-monoglycerides in benzene and chlorobenzene

Hardly any data are available on the behavior of oil-soluble, pure, nonionic detergents in solution. In view of this, a series of α-monoesters of glycerol and normal fatty acids (C 10, C 12, C 14, C 16, C 18) have been prepared. These compounds are surface-active in benzene and chlorobenzene. By means of light scattering, it is shown that they form small micelles in these solvents. In a better solvent, like chloroform, they exhibit molecular dispersion. It is found that small amounts of impurities, like free fatty acid and free glycerol, enhance the scattering considerably. The systems are not sensitive to traces of water. From the infrared spectra evidence is gained for the existence of intermolecular hydrogen bonding in the micelles in benzene, whereas only intramolecular hydrogen bonds are found to exist in chloroform. The experimental decrease in micellar size with increasing C-number, and the decrease in size when passing from benzene to chlorobenzene as a solvent, can be explained by existing theories.

N-terminal amino-acids of bovine eye lens proteins.

THE proteins of the crystalline lens are of particular significance to the embryologist because of the (serological) organ specificity of this part of the eye. In connexion with other biochemical and serological studies in our laboratory an investigation is being made on the N-terminal amino-acids of the main lens proteins : α-, β- and γ-crystallin. The preparations of α-crystallin have been isolated mainly by zone electrophoresis on starch1. They showed one single peak in both paper electrophoresis and moving-boundary electrophoresis at pH. 4.2; 6.2; 7.1; 7.8; and 8.9 respectively. In the ultracentrifuge only a very small percentage of impurities was still noticeable. Some preliminary experiments were also made on β- and γ-crystallin, which preparations were obtained by salting out with ammonium sulphate and still showed small amounts of impurities when investigated by electrophoresis and ultracentrifugation.

Thermal Conductivity: XIII, Effect of Microstructure on Conductivity of Single‐Phase Ceramics

The thermal conductivity of Al2O3, MgO, TiO2, and CaF2 single crystals and single‐phase poly‐crystalline aggregates of controlled microstructure was measured between 0° and 1000°C. The conductivity of pure single‐phase dense polycrystalline aggregates agrees with that of the corresponding single crystals at temperatures below the onset of radiant‐heat transfer. Small amounts of impurities and the pore geometry may considerably affect the conductivity of aggregates.