Colouring matters

Crude chlorophyll is prepared commercially from alfalfa meal or nettles by extraction with alcohol and partition into benzene. It is used as a colouring matter, particularly for foods and pharmaceutical products. 

It is extensively used in the preparation of dyestuffs. Combines with diazonium salts to form oxyazo-colouring matters. Gives rise to fluorescein dyes on fusion with phthalic anhydride. Used for production of plasticizers, resins, adhesives. 

REMOVAL OF TRACES OF COLOURING MATTER AND RESINOUS PRODUCTS USE OF DECOLOURISING CARBON... 

MAFF (1979), Interim Report on the Review of the Colouring Matter in Food Regulations, FAC/REP / 29, Ministry of Agriculture, Eisheries and Eood, Eood Additives and Contaminants Committee, HMSO, London, 1973. 

Dimethylaniline is also used for the preparation of tetra-methyldiaminobenzophenone(Michler s compound), which forms the basis of many colouring matters, and is obtained by acting upon dimethylaniline with phosgene (see p. 314))... 

An important group of colouring matters, known as the rhodamines, is obtained from phthalic anhydride and w-aminophenol and its derivatives. They hai e a constitution sinylai... 

The synthesis of pararosaniline from triphenylmethane is one which has gone far to solve the problem of the constitution of the important class of triphenylmethane colouring matters. 

The flowers were ext-aet by thre washings with petro eum spi it. Th thr sol t ons wei ni d, ried an filtered, hen the so cnt as distilled off, care being taken to exp t e last traces I tic w Th re idu m is distilla tion is a brown, vi cous mass compo d of vegetable wax th colouring matter and th essenti 1 il o the flowe... 

Accoiiding to Hanriot ionone can be detected in very minute amount by the following reaction If traces of it be dissolved in concentrated hydrochloric acid, the liquid becomes of an intense golden colour, and if the solution he warmed with chloral hydrate, a dirty violet colour results. The violet colouring matter is extracted by ether, and if the ether be evaporated a water-soluble violet-coloured residue is left. This test will detect 1 part of ionone in 2b00. 

Discolouration of products inside cans may follow the reduction of colouring matters or the formation of new coloured compounds with tin or iron. This is a problem with strongly coloured fruits and the remedy is to... 

Requirements for cans for beer and soft drinks differ from those for food cans in that (a) only low tin and iron contents can be tolerated in the product and (t>) the anticipated shelf-lives are much shorter. Specialised lacquering techniques including striping the seams are used to give complete cover to the metal. For soft drinks it is sometimes possible to select colouring matters and acids least likely to give rise to corrosion troubles, and rapid methods of testing formulations have been devised . Steel quality is also controlled by special tests. 

Lloyd, A.G., Extraction and chemistry of cochineal. Food Chem., 5, 91,1980. Yamada, S. et al.. Analysis of natural colouring matters in food (IV). Methylation of cochineal colour with diazomethane for analysis of food products, J. Agric. Food Chem., 41, 1071, 1993. 

Removal of traces of colouring matter and resinous prcsliicts... 

Lee HH. Colouring matters from Prismatomeris malayana. Phytochemistry 1969 8 501-503. 

Coagulation of natural rubber latex by stages with the object of removing the yellow colouring matter in the first fraction. The latex in the second fraction produces a white crepe rubber. See Bleaching Agent. 

AG Perkin and A E Everest, The natural organic colouring matters, (London Longmans, 1918). 

B I Stepanov in Recent progress in the chemistry of natural and synthetic colouring matters, Eds T S Gore et al. (New York Academic Press, 1962) 451. 

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