| abstract |
Ultra-violet absorbing agents have the formula:- where R' is H or SO3M and R'' is SO3M; M is H, a metal or an organic ammonium group. Cosmetic compositions contain the above cpds. for protection against light. The cpds. may also be used to protect human skin against U.V. rays. They protect against light of 280-315 nm but allow light of 315-320 nm to pass. Also the cpds. have improved solubility, particularly in water, compared with 3-benzylidene camphor or 4-methyl-3-benzylidene camphor. Prepn. is by reacting the corresponding cpd. where R" is H with conc. sulphuric acid, oleum or chlorsulphonic acid, followed by salt formation with a cpd. bearing the radical M. |