Spectrophotometric determination of erbium using kojic acid dye in different rare earth concentrates

A sensitive and selective spectrophotometric method was studied for the determination of erbium (Er) with kojic acid dye (koj) and cetylpyridinium chloride (CPC) as a cationic surfactant from Egyptian monazite and xenotime concentrates using third derivative spectrophotometry. The calibration curve was linear from 1 to 150 µg/mL erbium. The influence of various parameters and reaction conditions for optimum complex formation were investigated. The relative standard deviation for determination of 1 µg/mL erbium was found to be 1.5 after 5 repeated determinations with percentage error for Er determination from monazite and xenotime concentrates 6.4% and 4.48% respectively. The molar absorptivity of conventional and third derivative spectrum were 0.14 × 103 M−1 cm−1 and 0.13 × 103 M−1 cm−1 respectively and the detection limit was 1 µg/mL. Keywords: Erbium, Kojic acid dye, Cetylpyridinium chloride, Egyptian monazite, Xenotim

Predicting PVT properties of Egyptian crude oils by a modified Soave–Redlich–Kowng equation of state

The study aims to predict the physical properties of Egyptian crude oils using modified Soave–Redlich–Kowng equation of state. The modification was theoretically developed and then performed by using data of 43 black oil samples representing all active oil producing areas of Egypt. The equation enables to predict the bubble-point pressure, oil formation volume factor, gas–oil ratio, oil density, crude oil gravity, gas gravity and gas formation volume factor of black oils with average relative errors ranging from 0.01% to 10.713%. Calculation sensitivity of the proposed MSRKE is determined by testing four oil samples collected from different locations in Egypt and comparing the measured PVT properties with those calculated from MSRKE. These evaluations show an excellent agreement between the measured properties and calculated ones. The estimation of reservoir liquid and gas properties from MSRKE is often needed when detailed laboratory PVT data are not available