2. Add 50% NaOH solution to pH 12 with small portions. A solution of NaOH in distilled water (room temperature) is poured by drops, depends on the volume. When pH 12 is reached, an oily layer (amphetamine free base) forms on the top surface of Rm. The amount of amphetamine base is equal to the mass of dissolved amphetamine. The color can be from amber to transparent, depending on the purity of the salt.
3. Pour petroleum ether (20% by volume) into Rm and mix thoroughly. Let the layers separate. The ether is insoluble in water, as is the free base, but the base is soluble in ether. In this way, we remove some of the water-soluble impurities from amphetamine.
4. Separate the top layer with the extract into an another container using a plastic / glass syringe or separating funnel. If DCM was used instead of petroleum ether, then we separate the bottom layer. Avoid the ingress of water into the separated extract.
5. Wash the water (the remaining lower layer) with petroleum ether three times (5% of the water volume).
6. Combine the extracts.
7. Dry the extract with anhydrous MgSO4 for 1 hour, placing it in the freezer. The glass should be hermetically sealed.
MgSO4 is added to Rm 3-20% (depends on amount of water there) of the volume of ether. Drying is necessary to remove the remaining water from the ether, which in further stages, by dissolving the amph salt in water, will lead to a lower (by weight) yield of pure product. You can wrap it with cling film for container tightness. It must be closed to avoid saturation of the solution with moisture concentrating in the freezer. If MgSO4 is not available, keep Rm in the freezer for 12 hours. Then, in case of formation of water at the bottom of the container (in a layer or drops), the ether should be carefully decanted (poured out) without touching the water.
8. We filter the extract from MgSO4 that has absorbed water using a vacuum pump connected to a Buchner funnel with a Bunsen flask and a paper filter. You can use a conventional filter without vacuum, which will slightly reduce the yield (you have to wash the filter with an anhydrous solvent). The solution should be decanted onto the filter without lifting the sediment from the bottom. MgSO4 remaining at the bottom of the beaker has to be washed with an anhydrous solvent (pour it onto a filter) and disposed of.