The present disclosure relates to a benzoyl substituted carbazole-dioxazine pigment and its preparation. The process involves benzoylation of 3-nitro-N-ethylcarbazole in monochlorobenzene using benzoylchloride and ferric chloride to yield 3-nitro-6-benzoyl-N-ethyl carbazole, which on catalytic hydrogenation and subsequent condensation with chloranil and cyclization yields benzoyl substituted carbazole-dioxazine pigment.

The present disclosure is directed to compositions, kits, and methods for synthesizing a Schiff's reagent in situ, i.e., directly on a substrate, such as within a puddle disposed on the surface of a substrate. In some embodiments, the kits comprise at least a dye composition and a sulfite composition. In some embodiments, the dye composition comprises a compound having a 4-Benzhydrylidene-2,5-cyclohexadien-1-imine core functionalized to include at least two substituted or unsubstituted amine groups, wherein the compound has a molecular weight ranging from between about 300 g/mol to about 600 g/mol. In some embodiments, the dye composition optionally includes an acid. In some embodiments, the sulfite composition comprises a sulfite or SO.sub.2 source.

The present disclosure provides stabilized hematoxylin formulations having a pH of less than 2.4. In general, the stabilized hematoxylin formulations comprise a solvent, a hematoxylin dye, and an acid. The present disclosure also provides methods of using such stabilized hematoxylin formulations to stain biological samples. The present disclosure also provides for methods of readjusting the pH of a stabilized hematoxylin formulation to provide a hematoxylin staining solution.

The present disclosure provides stabilized hematoxylin formulations having a pH of less than 2.4. The present disclosure also provides methods of using such stabilized hematoxylin formulations to stain biological samples.

The present invention provides a food colouring composition, in particular the invention provides a composition or colouring composition comprising at least one Polyketide pigment (i) and one or more of the following compounds (ii) a carotenoid (such as lycopene, bixin and/or norbixin), rosmarinic acid, a chlorogenic acid, rutin glucoside, (gamma) cyclodextrin and/or a tocopherol.