Disclosed herein is a crystalline hemi-tartrate salt of the compound of formula (I-A), namely [5-(4,6-dimethyl-1H-benzoimidazol-2-yl)-4-methyl-pyrimidin-2-yl]-[3-(1-methyl-piperidin-4-yl)-propyl]-amine. Also disclosed is a process of preparing the hemi-tartrate of compound of formula (I-A) comprising: Dissolving the compound of formula (I-A) in an organic solvent forming a solution； Heating said solution to a first temperature in the range of from about 35 DEGREE C to about reflux； Adding L-tartaric acid to form a tartrate solution； and Heating said tartrate solution to a second temperature in the range of from about 50 DEGREE C to about reflux to form a heated mixture. Further disclosed is a process for the recrystallization of a hemi-tartrate of compound of formula (I-A) comprising: Dissolving the hemi-tartrate of compound of formula (I-A) in a mixture of water and an organic solvent, or in a mixture of organic solvents； and Removing a sufficient amount of water to yield a mixture with a boiling point of between about 78 DEGREE C and about 80 DEGREE C.
