PURPOSE: To manufacture the titled soap without necessity of driving off a large amt. of water and to use it as a cosmetic soap by incorporating a specified trialkylamine oxide dihydrate into a detergent compd.

CONSTITUTION: An amine (a) and at least stoichiometric conc. hydrogen peroxide org. ester (e.g. ethyl acetate) soln. are reacted at 25-100°C in an enough amt. of a solvent for holding a reaction mixture in a liq. state to obtain a trialkylamine oxide (B) of formula (wherein R' is an 8-24C primary alkyl; R" is methyl, ethyl or R'; R''' is methyl or ethyl). After a detergent compd. (A) used for an ordinary solid detergent is compounded with the ingredient B with an amt. of 5-80 wt.% of the obtd. solid detergent, molding, extrusion or form punching is performed.