Spot prevention in light-sensitive silver halide emulsion layers

Azamethine derivatives of phenols are prepared by reacting the half-ester of ethanolamine and sulphuric acid with salicyl aldehyde, 3,5-dichloro - 2 - hydroxybenzaldehyde or 2-hydroxy - 3 - methoxybenzaldehyde in the presence of potassium carbonate. The products may be reduced to the corresponding 2-substituted - aminomethyl - phenols by catalytic hydrogenation under pressure. Similarly, salicyl aldehyde is reacted with the sodium salt of taurin, the potassium salt of methyltaurin, or with 4-amino-butyric acid, the product of the latter reaction being hydrogenated. Similarly, glycine is reacted with 3,5-dichloro-2-hydroxy-benzaldehyde and the azamethine compound produced is hydrogenated, or 2,5-dihydroxy-benzaldehyde is reacted with glycine or 4-amino-butyric acid.