This data is related to the journal paper, “Employing constant rate filtration to assess active pharmaceutical ingredient (API) washing efficiency”. The data folder contains all the data used for this work. The folder named “Constant_rate_work_Exp_DataSet” contains all the raw experimental data that was obtained in the labs for all the experiments performed for this work. The folder named “Data_Analysis” contains analysis performed for all the experiments and also contains python script file used for some of data analysis work. Folder named “DOE” contains the files on Modde software used for DOE analysis for this work. Folder named “Solubility_Blue_Dye” contains experimental data for blue dye which is related to section 3.2 of the paper. Folder named “Mastersizer_Analysis” contains data obtained from particle size distribution analysis which is related to section 4.3 of the paper. Folder labelled “NMR_Analysis” contains all the data for NMR analysis that was performed on all the washed API cakes obtains from the experiments.