Effect of raw materials: The precursors are usually chosen with counter ions that can easily be decomposed to volatile products during heat treatment steps. Nitrates and carbonate salts are preferably used as metal precursors whereas ammonia or sodium carbonate as the precipitating agent. Chloride and sulphates ions act as poisons in many catalytic processes. Such ions should be avoided in the precipitation process. However if the precipitation is needed to be carried out in the presence of these ions then repeated washing steps are necessary to remove these ions from the precipitate. 

The nature of the counter ions present in the solution can also influence particle morphology, particle sizes and phase distribution.  It has been observed that preparation of MoO₃ from  Na₂MoO₄ precursor salt results in small particles with relatively high surface area whereas use of (NH₄)₆Mo₇O₂₄ as precursor salt results in larger particles.

Effect of pH: pH directly control the degree of super saturation and hence is expected to affect the final properties. But the influence of pH is not simple and has to be investigated experimentally for the specific system. In aluminium oxide system, the precipitation pH is one of the parameters that determines the phase formation. In general it has been found that precipitation in alkaline medium (pH > 8) leads to the formation of bayerite (β-Al(OH)₃), while precipitation in more acidic conditions favors formation of boehmite (γ-AlO(OH)).

Effect of concentration and composition: It is desirable to precipitate at high concentration levels of metal ions. This increases the space time yields by decreasing the vessel volume for the same mass of precipitate. Moreover higher degree of super-saturation leads to faster precipitation. Higher concentration levels also results in smaller particle size and higher surface areas due to increased nucleation rates.

If the catalysts are prepared by co-precipitation, the composition of solution determines the composition of the final product. Deviation from solution composition generally occurs if the solubilities of the different components differ significantly and the precipitation is not complete. The precipitation can be carried out simultaneously or sequentially. When the solubility of the components is not too different, then the precipitation will occur almost simultaneously. However, if the solubility of the components differs significantly then the component with lower solubility will preferentially precipitate resulting in sequential precipitation.

Effect of solvent:For preparation of bulk catalysts and supports, water is almost exclusively used as the solvent for economic reason. Organic solvents are much more expensive to use. Further more, solubilities of most metal salts used as the precursors are lower in organic solvents. Organic solvents are also environmentally hazardous. So use of organic solvents is very limited. These are used only in specific cases where product quality obtained is better by using organic solvent.