Spectrotitration of ethane-1-hydroxy-1,1-diphosphonic acid (EHDP(tm)) with thorium diaminocyclohexanetetra-acetate.
An automatic spectrotitration procedure for EHDP has been developed. It is applicable to samples containing 50mug or more of EHDP, with a relative standard deviation of 3% if no interfering materials are present. The sensitivity can be extended down to about 5mug, but titration blanks become significant and the standard deviation increases markedly. Thorium diaminocyclohexanetetra-acetate (Th-DCTA) is used as the titrant, to give a ternary species (Th-DCTA)(2)-EHDP. The end-point in the spectrotitration is due to deprotonation of Xylenol Orange indicator when it is incorporated into a weaker ternary species after all the EHDP has reacted. Salts such as NaCl, NaClO(4), Na(2)SO(4) and NaNO(3) interfere if present at concentrations of 0.1-0.5M. The method is much more sensitive to orthophosphate, but this interference can be averted by isolating the EHDP before titration by selectively adsorbing the phosphonate on calcium hydroxyapatite.
Determination of clodronate in aqueous solutions by HPLC using postcolumn derivatisation.
A method for the determination of clodronate at ppm levels in aqueous solutions by HPLC is presented. Clodronate is first separated by anion exchange chromatography using a solution of nitric acid and sodium nitrate as eluent. Th-EDTA-XO mixed ligand complex is used as a postcolumn reagent for clodronate. Clodronate reacts quantitatively with this complex in slightly acid solutions, and a change in the absorbance of Th-EDTA-XO is used as a measure for the clodronate concentration. The detection limit is about 3 ppm, and the linear dynamic range of the method extends up to about 200 ppm. The RSD values varied between 5 and 16%. The effect of pH on appearance and retention of different forms of clodronate is studied. Different forms of clodronate can be separated and detected in the used anion-exchange system.
Design of reinforced concrete lining in pressure tunnels, considering thermal effects and jointed rockmass
Abstract Jaeger's theory (Jaeger, Rock Mechanics and Rock Engineering , Cambridge University Press, 1972) of the design of the lining for a pressure tunnel applies to a tunnel located in an isotropic, homogeneous and elastic medium. The theory is derived from the elasticity equations for the plane stress condition. In this paper, Jaeger's theory is extended to a plane strain situation. Also included is a discussion of the effects of a uniform increase (or decrease) in the lining temperature, jointed rockmass, cracking of the tunnel lining, and cracking of the rockmass around the opening. Tables are presented for the modulus of subgrade reaction for various rockmass conditions and for rock sharing pressures for various lining conditions. The reduction factor to include the effect of joints in rockmass is derived by the analysis of a numerical model of the lined tunnel by the finite-infinite-interface element method.