Cleaning by 3 x recrystalization: Put MINIMUM quantity of hot (40 C) DRY DCM (or dry 98+% Ethanol) in the flask until the last remains of the dry stuff dissolves, and add 4 x this DCM-quantity in the form of DRY acetone. Close with stopper and put 1 hr in freezer. A solid dirty-white crystal mass is formed with a layer of dark red fluid on top of it. Decant the fluid and repeat this step another 2 x and 2 Hrs. You have, the last time, snow white crystals. Dry Weight = 141,5 gram, close to quantitative yield.
You can eventually melt this crysta