Photosensitive redox solutions

Abstract

The invention provides aqueous solutions of (1) the reaction product of anhydrous trimethyl borate with titanium tetrachloride and (2) polyvinyl alcohol, preferably not exceeding about 0.5 weight percent of each. These solutions have a pH of about 1, but when ammonium hydroxide is added, the pH may be raised to about 10 without precipitation of titanium or gelation of the polyvinyl alcohol. When the pH of the above solutions is adjusted to between about 2 and about 10, the solutions are photosensitive. When these solutions are in a confined zone, sunlight or actinic radiation in the range between ultraviolet light and the lower wavelengths of the visible spectrum causes oxygen from the air above the solutions to be consumed until it is all gone. Then, reduction of the colorless dissolved Ti(IV) compound to the dark blue Ti(III) state occurs without precipitation of the Ti(III) product or reoxidation to Ti(IV). The blue Ti(III) solution is quickly reoxidized by reexposure to air. Similar photosensitive solutions are formed with polyvinyl alcohol and other Ti(IV) compounds, such as (1) the tetravalent titanium compound conforming substantially to the formula Cl.sub.2 Ti(OR).sub.2 where R is H, CH.sub.3, C.sub.2 H.sub.5, C.sub.3 H.sub.7 or C.sub.4 H.sub.9 ; (2) titanyl sulfate, and (3) titanyl chloride. The polyvinyl alcohol may be replaced by other complexing agents, such as N-hydroxyethylenediaminetriacetic acid, diethanolglycine, glucoheptanoic acid, arabonic acid, gluconic acid, galactonic acid, saccharic acid, mucic acid, and the sodium and ammonium salts of these compounds.