n butylether as well as dimeric or trimeric polyethers coronands cryptands spherands etheramines like for example 2 methoxyethylamine etc from the group of amines it is preferable to use aliphatic amines and among these low primary or secondary aliphatic amines examples of suitable amines are primary secondary or tertiary aliphatic and alicyclic monoamines or polyamines methylamine ethylamine 1 and 2 propylamine 1 and 2 butylamine ethylene diamine tri tetra penta hexamethylene diamine dimethylamine diethylamine di n propylamine cyclopentyl and cyclohexylamine nitrogen heterocycles and perhydro nitrogen heterocycles for example piperidine 1 2 aminoethyl piperazine 1 2 aminoethyl pyrrolidine and 1 2 aminoethyl piperidine 4 2 aminoethyl morpholine furthermore liquid ammonia is also suitable for the same purpose as an alternative to the amines certain amides can also be considered for example the following can be used 1 3 dimethyl 3 4 5 6 tetrahydro 2 1h pyrimidon dimethylpropylene urea dmpu 1 3 dimethyl 2 imidazolidinon n n dimethylethylene urea dmeu 1 methyl 2 pyrrolidon nmp 1 ethyl 2 pyrrolidon n n diethylacetamide n n diethylpropionamide n n diethylisobutyramide the separate addition of a source of hydrogen can be omitted if it is known that a substance which is suitable as a source of hydrogen is already present in sufficient quantity in the mixture which is to be treated the mechanical processing as described in this invention.