Salts of the 1:2 chromium complex of 4-(5'-chloro-2'-hydroxy-3'-sulfophenylazo)-3-methyl-1-phenylpyrazol-5-on e and 4-(3', 5'-dichloro-2'-hydroxyphenylazo)-3-methyl-1-phenylpyrazol-5-one

Granted: Oct 21, 1986 Filed: Sep 22, 1981

This patent predates the USPTO's electronic file wrapper — prosecution documents from this era exist only in the Patent Office's paper records. A certified copy of the file history can be ordered from the USPTO's paper archives.