Cochineal, Carmine Red

In dyeing, this product gives much bluer shades, and is used for modifying cochineal scarlets. 

Carmine-red is prepared from the lake obtained by precipitating a cochineal decoction with lead acetate. This lead lake is dissolved in dilute sulphuric acid, freed from lead by sulphuretted hydrogen, and boiled with very dilute sulphuric acid for some hours. Barium carbonate is added till a violet coloration ensues, and then filtered rapidly and precipitated with lead acetate. The lead lake is decomposed and the filtrate evaporated to dryness in vacuo. 

Carmine-red is a dark red substance, which appears green by reflected light. It is insoluble in ether, but soluble in water and alcohol with a red colour, lleducing agents convert it to a colourless compound. On fusion with potash carminic acid yields coccinin [80], and on heating with water to 200° ruficarmine is formed [82]. 

By boiling carminic acid with nitric acid, trinitrococcussic acid (trinitrocresotinic acid), 

Bromine reacts with carminic acid, producing two brominated compounds, a-bromcarmine, CioH Br Os [81], forms colourless needles, M.P. 248°, which are soluble in alkalies. On boiling with strong potash solution it yields oxybromcarmine, which behaves like an oxyacid of the formula 

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