Hi I am currently writing a lab report and have a few questions .A quick rundown of the lab.acid base extraction.

Hi I am currently writing a lab report and have a few questions .....A quick rundown of the lab....acid base extraction......an analgesic made of acetandile , acetylsalicyclic acid and sucrose was the starting compound( Phensuprin) and each one of the indvidual compents were isolated. Sucrose was isolated first by add methylene chloride and gravity filtration was used to collect the solid. The organic layer was then extracted two separate times using 25 ml of sodium bicarbonate. The dichloromethane layer was separated from the aqueous layer . The aqueous layer was cooled and about 10 ml of HCL was added and then the solid was collected by vacuum filtration. This is how the acetylsalicyclic acid was recovered.. The dichlromethane solution dried over anhydrous sodium sulfate. This was then put into a round bottom flask and the methylene chloride was removed using a rotary evaporator.This is how the acetandile was recovered. My data:  Acetandile - .5 g recovered. 24 % recovery. 20% mass composition of phensuprin       Acetylsalicyclic acid - .717 g recovered. 34 % recovery.  27% mass composition.   Sucrose .55 g recovered. 26% recovery.   52% mass composition.    So my questions........ What impurity is left over in the acetandile? Is it possibly some drying agent or water?? or acetylsalicyclic acid? Also is perhaps the salt that was formed in the aqueous layer before the HCL was added still in the acetylsalicyclic acid? and that is why is has a larger percent recovery......thanks!!!