Spectrum Chemical manufactures and distributes fine chemicals with quality you can count on including those with CAS number 69-78-3, Whether you call it 5,5�-Dithiobis(2-nitrobenzoic Acid), 3-Carboxy-4-nitrophenyl Disulfide or DTNB you can be assured the 5,5�-Dithiobis(2-nitrobenzoic Acid) products offered by Spectrum, meet or exceed the grade requirements or specifications for each individual product.