Search

The kinetics of the forward and backward extractions of copper(II) by the bis‐(2, 4, 4‐Trimethylpentyl)phosphonic acid process have been investigated using the single drop technique and flux (F)‐method of data treatment. The (F)‐equation for the forward extraction of Cu(II) from the sufate‐acetato medium by bis‐(2, 4, 4‐trimethylpentyl)phosphinic acid can be represented by: Ff(kmol m–2s–1) = 10–8.64[Cu2+](ini)$ [{\rm H}^+]^{-1}_{\rm (int)} $$ [{\rm H}_2 {\rm A}_2]^{0.5}_{\rm (o)} $[HSO4–]1. Analysis of this equation gives, Ff(kmol m–2s–1) = 10–4.88[CuHSO4+] [A–]. An activation energy of ca. 13.7 kJ mol–1indicates that the diffusions of CuHSO4+and A–to the aqueous film of the interface (and not the chemical reaction between these two species to form CuHSO4.A) are rate controlling. The (F)‐equation for the backward extraction of Cu(II) from the [CuHSO4A.HA] complex in the organic phase by an aqueous sulfate‐acetato solution can be expressed as: Fb(kmol m–2s–1) = 10–5.68[CuHSO4A.HA](o)(1 + 10–3.67[H+]–1)–1$ [{\rm H}_2 {\rm A}_2]^{-0.5}_{\rm (o)} $$ [{\rm SO}^{2-}_4]^{-1} $. Analysis of this equation results in two equations, Fb(kmol m–2s–1) = 10–9.797[CuHSO4A.HA](o)[A–]–1[HSO4–]–1and Fb(kmol m–2s–1) = 10–8.127[CuHSO4A.HA](o)[A–]–1$ [{\rm SO}^{2-}_4]^{-1} $at higher and lower aqueous acidities, respectively. Low activation energies (< 20 kJ mol–1) indicate that the stripping processes are diffusion controlling at both regions of H+concentration. The value of Kex (rate)(kf/kb= 10–2.967) matches well with the Kex (eq)(10–3.19) value within the experimental limitations.

Abstract

This study was designed to investigate differences in personality type and sex of subjects on critical flicker frequency (CFF) of normal and problem-children from two secondary schools. Students, 20 problem-children and 20 normal children, were tested on critical flicker frequency. Both sexes were equally represented in the two groups. An Arabic version of Lanyon's Psychological Screening Inventory was given. Individuals in the problem group were antisocial in their behaviours and attitudes, extraverted, maladjusted, and had a lot in common with psychiatric patients. A 2-way analysis of variance showed that both sex of subject and type of personality were significantly related to CFF. Boys obtained significantly lower mean CFF than girls and problem-children obtained significantly lower mean CFF than normal children. An interaction of sex of subjects and type of personality with CFF was also found. The results were not as hypothesized and contrary to prior reported findings.

This study investigated the relationship between achievement motivation and academic performance of 67 college students in Zambia. Achievement motivation was measured by applying a modified version of Lynn's achievement motivation questionnaire and academic performance was measured by averaging the grades of term examinations. A Pearson product-moment correlation indicated a significant positive relation between achievement motivation and academic performance. The practical significance was discussed. It is suggested that achievement motivation training programs for underachieving students in developing countries might improve their academic performances.

Two experiments are reported which investigated the effects of fasting on visual flicker fusion (VFF). In Exp. 1 the VFF of 40 undergraduate students, 20 men and 20 women, whose mean age was 22.5 yr., was measured in nonfasting conditions 1 to 2 weeks before and in fasting conditions during the Muslim fasting month of Ramadan. In Exp. 2 the VFF of a comparable group of 15 men and 15 women, whose mean age was 23.2 yr., was measured in a different month in both fasting and nonfasting conditions. Subjects were assigned randomly to these two conditions. Analysis shows that fasting reduced VFF significantly in both experiments. This finding indicates that fasting is likely to reduce perceptual sensitivity. The results were explained in terms of fatigue and physical exhaustion effects produced by fasting.

Critical flicker frequency of 40 undergraduate students, 20 men and 20 women whose mean age was 19.3 yr., was measured under monocular and binocular viewing conditions, using the Lafayette Visual Perception Control with Display Unit. Half of the subjects received monocular treatment first and binocular treatment second, and the other half received the treatments in the reversed order. A 2-min. rest was allowed between these treatments. Analysis shows that mean CFF under the monocular condition was significantly lower than that under binocular conditions. The findings were discussed in terms of visual constraint and eye strain and fatigue under the monocular viewing condition.

Fourteen commercial hybrid cultivars of sorghum grain were examined for physical characteristics before and after being milled by abrasion. Milling to 10% total loss in weight resulted in the pigments in the pericarp being effectively removed but colour spots on the hilar and germ remained on most cultivars and the testa was exposed on some cultivars. Milling showed that the cultivars were of varying degrees of hardness but all gave >80% yield of unbroken kernels with the germ attached. The milled grains were boiled like rice but the cooking time was high for all cultivars (range 57–64 min) although the water uptake and swelling of the cooked grain was satisfactory and the solids lost during cooking was low.

Critical flicker frequency (CFF) of 40 men, 20 mentally retarded whose mean age was 22.0 yr. and 20 normal whose mean age was 21.5 yr., was measured under binocular viewing using the Lafayette Visual Perception Control with a display unit. Subjects had been previously tested for visual acuity and color blindness. Analysis showed a significant difference in CFF between mentally retarded persons and normal individuals, the former having lower CFF than the latter. This finding suggests lower perceptual sensitivity of the mentally retarded persons. Further research with provision for EEG recordings is suggested.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.