Examples of index fossils. Index fossils (also known as guide fossils, indicator fossils or zone fossils) are fossils used to define and identify geologic periods (or faunal stages).
Methyl cellulose. Methyl cellulose (or methylcellulose) is a chemical compound derived from cellulose. It is a hydrophilic white powder in pure form and dissolves in cold (but not in hot) water, forming a clear viscous solution or gel.
Solubility Rules The solubility of ionic compounds in aqueous solutions is wide and varied. Some compounds are highly soluble (e.g. NaCl), some compounds are moderately soluble (e.g. SnI2) and some compounds are highly insoluble (e.g., AgCl).Determining which compounds are soluble and not soluble in a water medium is not a simple task.However, a set of rules that help in this regard can be stated.These rules are known as solubility rules. Below is a set of solubility rules.ome compounds are highly soluble (e.g. NaCl), some compounds are moderately soluble (e.g. SnI2) and some compounds are highly insoluble (e.g., AgCl). Determining which compounds are soluble and not soluble in a water medium is not a simple task.