Revista de Ciências Químicas

Grease is a mixture of a fluid lubricant usually petroleum oil and a thickener (soap) dispersed in the oil. The base oil (i.e., petroleum oil) can be substituted with recycled waste lubricating oil. Since the petroleum prices increase yearly, the use of recycled waste lubricating oil as base oil for greases production becomes the best solution to this problem. Sodium soap thickener was formed by reacting sodium hydroxide with palm kernel oil. The production of low-cost sodium grease was achieved. Three different waste lubricating oil samples (150 N, 350 N, 600 N) were recycled and analyzed, to determine the quality of the recycled lubricating oil samples. The results are tabulated. The recycled waste oils were used to produce sodium greases. The produced greases were tested for dropping point (600 N=180, 350 N=160, 150 N=145)°C, worked penetration (180 N=220, 350 N=240, 150 N=300), moisture content (Insignificant), appearance (fibrous and buttery), finger impression (adhesive) and water resistance (susceptible to water). This production was bound by a technology which embraces saponification, evaporation, melting of soap formed and blending with calculated quantity of base oil at the temperature ranging from 170°C to 180°C. The result obtained from the analysis showed that two out of the three products fall within the American Society for Testing of Materials (ASTM) and National Lubricating Grease Institute (NLGI) standard specifications for ball-bearing grease No. 2 and No. 3 respectively. However, the products of this research are economical in terms of cost and availability of raw materials in Nigeria, when compared with imported greases like the Abro-products.

The synthesis of poly-p-chloroaniline (PpCA) by oxidative chemical polymerization using potassium dichromate as oxidizing agent was carried out. The optimum conditions for the polymerization reaction and the order of reactions and thermodynamic activation parameters were investigated. A molecular mechanism for the oxidation of p-chloroaniline using potassium dichromate is proposed. The TGA analysis and spectroscopic studies IR, UV-vis and elemental analysis have evidenced the structure of polymeric chain. The surface morphology of the obtained polymer was characterized by X-ray diffraction and transmission electron microscopy (TEM). Moreover, determinations of dielectric properties of the prepared polymer were carried out. The a.c conductivity (σac) of (PpCA) was investigated as a function of frequency and temperature. The microscopic conduction mechanism of charge carries over the potential barrier in polymer backbone was found classical hopping model. The electronic structure of neutral PpCA, radical cation and dimer radical cation are investigated theoretically at the B3LYP/6-311G** level of theory. The mechanism of the polymerization process is discussed and analyzed. The calculated EHOMO and ELUMO energies of the studied compounds can be used to calculate the global properties; chemical hardness (η), softness (S) and electronegativity (χ). The calculated nonlinear optical parameters (NLO); polarizibilty (α), anisotropy of the polarizibility (Δα) and first order hyperpolarizibility (β) of the studied compounds show promising optical properties. 3D-plots of the molecular electrostatic potential (MEP) for neutral monomer and radical cation dimer are investigated and analyzed showing the distribution of electronic density of orbitals describing the electrophilic and nucleophilic sites of the neutral monomer and radical cation dimer.

Concentration of iron was determined in vegetables of spinach, cabbage and potato randomly purchased from local markets of Gubrie and Wolkite Town and analyzed using UV-Vis spectrophotometry by thiocyanate colorimetry. The concentration of iron in potato (Solanum tuberosum), Cabbage (Brassica oleracea var. capitata) and Spinach (Spinacia oleracea) was 1.10 ± 1.29 × 10-3 mg/100 g, 0.931 ± 1.29 × 10-3 mg/100 g and 1.08 ± 2.36 × 10-3 mg/100 g respectively. The level of iron in each vegetable samples were lower than FAO/WHO guidelines (0.03 mg/100 g). In addition, cabbage shows a highest mean moisture content (95%) and potato shows the least moisture content (83%). according to Analysis of Variance (ANOVA) at 95% confidence level, the mean moisture content percentage between vegetable samples is statistical significance difference and there is no statistical significance difference in mean concentration of iron. The observed differences in moisture contents in each vegetable samples may as a result of variation in soil type, difference in capacity of preventing water from evaporation.