AN INVITRO EVALUATION OF THE DISSOLUTION POTENTIAL OF VARIOUS BEVERAGES ON ENAMEL THROUGH ANALYSIS OF pH AND CALCIUM IONS RELEASED.

Background: Beverage consumption is considered as one of the important risk factors for dental erosion.The purpose of the present study is to evaluate the enamel dissolution potentials of commercially available beverages through pH analysis and quantification of calcium ions released. Materials and Methods:- Four commercially available beverages, Green tea (TETLEY LTD), Red bull energy drink (RAUCH FRUCHTSAFTE, GMBH&CO OG, UAE), Real mixed fruit juice (real fruit power ltd, DABUR), Appy fizz (PARLE AGRO) were used to analyse pH and calcium ions released through two independent phases. 24 enamel specimens were prepared from 12 healthy human molars. pH analysis was done with pH meter and calcium analysis was measured by using colorimetry and spectrophotometry. Statistical analysis was carried out by using tests of descriptive statistics, paired t test for intra group comparisons and One way ANOVA with Post Hoc tukey test for intergroup comparisons. Results: Mixed fruit juice had shown highest acidic potential while Green tea had shown lowest acidic potential. Red Bull had shown highest dissolution potential while green tea had shown lowest dissolution potential. Conclusion: Dental erosion is influenced by the pH of the beverages and calcium dissolution of the tooth. Red bull has shown highest erosion potential. Even though green tea with an high acidic pH did not show any considerable erosion potential.. Key words: Dental erosion, pH of beverages, dissolution potential of beverages

Relating thermohaline simulation of salt dissolution to land collapse at a Transylvanian salt diapir, Romania

<p>The presented study estimates salt dissolution caused by groundwater around a salt diapir in the Transylvanian Basin, which is facing land-collapse hazards related to historic salt mining activities. Because the amount of salt dissolution is controlled by the concentration gradients and fluxes near vulnerable areas of the salt dome, specific attention has been given to hydrogeological boundary conditions. They include the hydraulic role of possible more permeable fault zones along the salt dome, and the potential access to the salt diapir of over-pressurized subsaturated groundwater within regional scale sandstone layers. A structural three-dimensional (3D) model of the salt diapir, the adjacent basin sediments, and the mining galleries was developed based on existing maps, borehole data, own field observations, and geological publications of the Transylvanian Basin. The salt dissolution potential was simulated with 2D vertical thermohaline flow and transport model scenarios along the southeastern flank of the diapir. Results showed that the following factors increase the salt dissolution capacity along the upper 180 m of the diapir: (1) the presence of more permeable Quaternary alluvial sediments in connection with a fault zone of higher permeability along the diapir, and (2) the presence of more permeable sandstone units within the Miocene sediments in the east of the diapir, which provide freshwater access to the upper parts of the diapir. Thermohaline simulation with viscosity variation of the fluid, instead of a constant viscosity, influences the resulting salt fluxes by up to 50% within studied temperature ranges of 10 to 60°C in the model domain. The range of theoretical dissolution rates along the upper 180 m of the diapir supports the hypothesis that cavern collapse is more likely to occur where cavern side walls have already been mined to almost no remaining side walls of rock salt, which is the case in the southeastern part of the diapir. A past land collapse from 2010, which formed a 70-90 m wide saline lake, has occurred in this area southeast of the diapir appearing to be the more vulnerable to land collapse.</p><p>Zechner, E., Dresmann, H., Mocuţa, M., Danchiv, A., Huggenberger, P., Scheidler, S., Wiesmeier, S., Popa, I., Zlibut, A. (2019): Salt dissolution potential estimated from two-dimensional vertical thermohaline flow and transport modeling along a Transylvanian salt diapir, Romania, Hydrogeol. J., 27, 1245-1256, https://doi.org/10.1007/s10040-018-1912-1.</p>

Anodic behaviour of Cu, Zr and Cu–Zr alloy in molten LiCl–KCl eutectic

The anodic dissolution behaviours of Cu, Zr and Cu–Zr alloy were analysed in LiCl–KCl at 500°C by anode polarization curve and potentiostatic polarization curve. The results show that the initial and fast-dissolving potentials of Cu are −0.50 and −0.29 V, and Zr are −1.0 and −0.88 V, respectively. But, in the Cu–Zr alloy, the initial and fast-dissolving potentials of Cu are −0.52 and −0.41 V, and Zr are −0.96 and −0.92 V, respectively. The potentials satisfy the selection dissolution principle that Zr in the alloy dissolves first, while Cu is left in the anode and is not oxidized. The passivation phenomenon of Zr is observed in the quick dissolution of Zr, while it is not observed in the Cu–Zr alloy. Moreover, from the above anodic dissolution results, potentiostatic electrolysis of Cu–Zr alloy was carried out at −0.8 V for 40 min, and the anodic dissolution mechanism and kinetics of Zr in Cu–Zr alloy were also discussed. In the initial stage, Zr dissolves as Zr 4+ ions from the alloy surface and enters into the molten salt, leaving a Cu layer called ‘dissolving layer’ on the surface of the alloy. After that, another layer between the matrix and ‘dissolving layer’ called ‘diffusion–dissolution layer’ appears. Zr diffuses in the alloy matrix and dissolves as Zr 4+ ions on the surface of the ‘diffusion–dissolution layer’ continuously, and Zr 4+ ions diffuse through the ‘dissolving layer’ and enter into the molten salt finally. In addition, the factors affecting the dissolution of Cu–Zr alloy, such as time and potential, were also investigated. The dissolution loss increases with the increasing dissolution potential and time, while the dissolution rate increases with the increasing dissolution potential and declines with the prolonging dissolution time.

Selection of Complete Recovery of Precious Metals in the Processing of Copper-Nickel Alloys in Hydrometallurgical Way

This article deals with the key aspects of how to determine the dissolution potential of copper-nickel base alloys containing precious metals in a lab environment and select conditions for their dissolution. The work indicates the composition of the anode under research and presents the dependence graphs of the potentials on time and stress. It also explains the effect of some impurities on the process.