help please

Sometimes you see solid precipitation at the bottom of the filtration flask. It may not mean your filtration is unsuccessful. What can be the possible cause(s) of this? Solvent(s) evaporates slowly. Less amount of solvent leads to more precipitation. Filter paper broke which leads to solid not being filtered thoroughly (on rare occasions). Bring filtrate back to filtration again using new filter paper if this is the case. The filter paper was not wet or moistened prior to the filtration. Some solid particles get through from the edge of the filter paper without being filtered. Temperature will decrease in the filtrate due to presence of vacuum & evaporation of solvents. Solubility decreases and leads to precipitation