Ring cleavage occurred when 1,2,4-triazino-1,2,4-triazines (3), (4) and (5) were treated with concentrated hydrochloric acid to yield N-substituted triazines (7) and (8). These confirm the given configuration assigned to the isomeric triazinotriazines. 6-Methyl-2-phenyl-7H-oxazolo [3,2-b][1,2,4]-triazin-7-one (9) underwent ring cleavage on treatment with sodium alkoxide to afford 3-alkoxy-1...

This study aimed at testing how active and inactive enamel caries lesions differ by their degree of resin infiltration, and whether the choice of acid pretreatment plays a crucial role. Four examiners assessed 104 human molars and premolars with noncavitated enamel lesions and classified them as 'active' or 'inactive' using the Nyvad criteria. Forty-five teeth were included in this study after ...

G . H evesy has written that [6] 1 " In view of the I.great similarity b etween hafnium and zirconium, i t ris hardly possible to separate these two elements in a lsingle operation ." A simple one-step separation c adequ a te for analytical work has still to be developed for hafnium-ziTconium mixtures, although recent work employing ion exchange has developed suitable methods for the separation...

Chemical recycling of Polyethylene terephthalate, PET, wastage has been investigated in this study. The aim of this work is recovery of terephthalic acid and ethylene glycols from PET waste. This process has been done in two stages. At the first stage, reaction between PET waste and sodium hydroxide for production of ethylene glycol and sodium terephthalate solution carried out in a stainless s...

Our study aims to decompose phosphogypsum (PG), mainly composed of CaSO4.2H2O, by reduction in an acidic medium. We evaluated the decomposition PG various reaction mechanisms. Sulfate ions from acid digestion are reduced sulfide hydrogen gas produced solution hydrochloric attack metal iron. The solid residues obtained have been determined and monitored X-Ray Diffraction, Fourier-Transform Infra...

The chemical potentials of each solute in an aqueous mixture of two electrolytes have been determined for many systems. For example, the activity coefficients of both hydrochloric acid and sodium chloride in mixed aqueous solution have been derived from emf measurements [I]. The isopiestic vapor pressure method has been used [2] to determine the activity coefficients of each solute in aqueous m...

The chromophore of C-phycocyanin, phycocyanobilin, was cleaved from the protein with methanol, concentrated hydrochloric acid, or subtilisin BPN’. The pigments obtained were converted to their dimethyl esters and purified by preparative high pressure liquid chromatography and examined for purity by analytical high pressure liquid chromatography on silica gel. They were characterized by proton t...

Teaching high school students about the digestive system can be a challenge for a teacher when s/he wants to overcome rote learning of facts without a deeper understanding of the physiological processes inside the alimentary tract. A series of model experiments illustrating the journey of a sandwich was introduced into teaching high school biology. Using a computer equipped with a commercially ...