This document discusses different types of drugs and their sources, manufacturing processes, storage conditions, and decomposition. It also covers limit tests, which are used to identify and quantify impurities. Specific limit tests are described for iron, arsenic, and sodium nitrite. Non-aqueous titrations are discussed as a method to titrate weak acids and bases using solvents like acetic acid. Beer's law and its use in UV-Vis spectrometry to determine analyte concentration is also summarized.