Abstract: A process for preparing guanidine derivatives, in particular creatine, is described and entails an O-alkylisourea salt and a primary or secondary amine being reacted in the presence of crystals of a guanidine derivative.

Abstract: In a process for preparing crystalline NaOH.3.5H.sub.2 O, NaOH.3.5H.sub.2 O is allowed to crystallize from an aqueous sodium hydroxide solution which contains sodium chloride and is saturated in respect of NaOH.3.5H.sub.2 O and the crystals formed are separated from the solution using a mechanical solid/liquid separation apparatus, wherein the solid/liquid separation is carried out under conditions under which the crystalline NaOH.3.5H.sub.2 O is freed sufficiently of residual solution adhering to the surface for the sodium chloride content of the crystalline NaOH.3.5H.sub.2 O obtained to be less than 100 mg per kg. The crystalline NaOH.3.5H.sub.2 O is subjected to an additional purification step, which may include the at least superficial melting or the at least superficial dissolution of the crystals, in combination with a solid/liquid separation step. The additional purification step. The additional purification step comprises washing the crystalline NaOH.3.5H.sub.2 O separated off.

Abstract: A crystalline solid which has a sufficiently low hygroscopicity for processing and use and essentially consists of glycine-N,N-diacetic acid derivatives is prepared by adjusting the water content of the starting material containing the glycine-N,N-diacetic acid derivatives to a value of from 10 to 30% by weight, based on the starting material, and subsequently bringing about crystallization.