A study of the reaction of pentacyclic triterpenoids with concentrated sulfuric acid
SummaryThe conditions for the reaction of triterpenoids with concentrated sulfuric acid have been studied by the method of mathematical planning, and the optimum conditions for performing this reaction have been found.
Zur spektralphotometrischen Bestimmung von steroiden und triterpenoiden Verbindungen
Sterole, Steroide, Steroidsaponine, Triterpensaponine und deren Aglykone weisen bei der spektralphotometrischen Messung in konzentrierter Schwefelsäure im UV‐Bereich eine Absorptionsbande auf, die zur quantitativen Bestimmung der genannten Verbindungen verwendet werden kann. Die Messung kann mit den freien oder an ein DC‐Sorptionsmittel adsorbierten Verbindungen durchgeführt werden. Die Schwefelsäureumsetzungsprodukte wurden isoliert und analysiert, jedoch konnte der Reaktionsmechanismus noch nicht endgültig aufgeklärt werden.
Effects of the mineral phase and valence of vanadium on vanadium extraction from stone coal
The influence of roasting on the leaching rate and valence of vanadium was evaluated during vanadium extraction from stone coal. Vanadium in stone coal is hard to be leached and the leaching rate is less than 10% when the raw ore is leached by 4 mol/L H2SO4 at 90°C for 2 h. After the sample is roasted at 900°C for 2 h, the leaching rate of vanadium reaches the maximum, and more than 70% of vanadium can be leached. The crystal of vanadium-bearing mica minerals decomposes and the content of V(V) increases with the rise of roasting temperature from 600 to 900°C, therefore the leaching rate of vanadium increases significantly with the decomposition of the mica minerals. Some new phases, anorthite for example, form when the roasting temperature reaches 1000°C. A part of vanadium may be enwrapped in the sintered materials and newly formed phases, which may impede the oxidation of low valent vanadium and make the leaching rate of vanadium drop dramatically. The leaching rate of vanadium is not only determined by the valence state of vanadium but also controlled by the decomposition of vanadium-bearing minerals and the existence state of vanadium to a large extent.