Process for the purification of cellulose and starch ethers

The process for the purification and isolation of a crude reaction product comprising a cellulose or starch ether suspension by removing the suspending agent, said process comprising introducing the cellulose or starch ether suspension into a solid jacket sieve worm centrifuge, separating off the suspending agent leaving a moist solid which is then conveyed to the filter zone of said centrifuge, uniformly contacting the moist solid with a purifying agent, separating the purifying agent from the solid by centrifuge and recovering purified cellulose or starch ether solid.