Cochineal. Technical Preparations of Cochineal.(CHAPTER I. The Anthraquinone Group.)(Osa artikkelista)

The Natural Organic Colouring Matters
By
Arthur George Perkin, F.R.S., F.R.S.E., F.I.C., professor of colour chemistry and dyeing in the University of Leeds
and
Arthur Ernest Everest, D.Sc., Ph.D., F.I.C., of the Wilton Research Laboratories; Late head of the Department of Coal-tar Colour Chemistry; Technical College, Huddersfield
Longmans, Green and Co.
39 Paternoster Row, London
Fourth Avenue & 30th Street, New York
Bombay, Calcutta, and Madras
1918

Kaikki kuvat (kemialliset kaavat) puuttuvat // None of the illustrations (of chemical formulas) included.

Ammoniacal Cochineal.

When a solution of carminic acid in ammonia is allowed to stand for some time, there is formed a new compound, which appears to consist of carminic acid in which one of the hydroxyls has been replaced by an amino group. The formula assigned to this substance by Schützenberger was C₉H₉NO₄. This reaction, long known, has been utilised for the production of a new colouring matter termed ammoniacal cochineal, or carminamide, and this comes into commerce either as cakes or in the form of a paste.

The first variety is usually prepared by allowing one part of cochineal to stand in a closed vessel for three months with three parts of ammonia. The clear liquid is decanted, treated with about half its weight of gelatinous alumina, evaporated, and when the mass has become thick, it is cut up into cakes and dried.

The paste is manufactured in a somewhat similar manner, the ammonia, however, being only allowed to react for eight days. The clear liquid is then evaporated to about one-third its bulk without addition of alumina (Crookes, "Dyeing and Calico Printing ").

Ammoniacal cochineal dyes much bluer shades than cochineal itself, and it is sometimes employed in conjunction with the latter. Its use is now very limited, but it finds some application in the blueing of bleached cotton.