This section is from the book "Monograph on Flavoring Extracts With Essences, Syrups, and Colorings", by Joseph Harrop . Also available from Amazon: Monograph On Flavoring Extracts With Essences, Syrups And Colorings.
The proper employment of colorings in the various formulas given in this work is of considerable importance, more especially the kinds fit or best fitted to be used.
Our observation, extending through some years, has led us to the belief that very many of the flavoring extracts of the market are colored with aniline. These substances (the various salts of the base aniline), without doubt contain a poison, which in many instances has been found, on analysis, to be arsenic, and which has been said by expert chemists to be much more active in combination with aniline than when in a separate condition. The facts, as stated, appear to have led to such a conclu sion. The inducement for such a substitution can only be accounted for on the grounds of cheapness. The fact admitted, the injurious effects proven, the cause economy only, then we need not ask for excuse, but rather for a law to prohibit its use and punish the offender. Such mixtures, passing into the stomachs of the people, can only enfeeble and destroy the race.
*Juices, Syrups or Extracts, colored with Fuschin, color a woolen or silk thread permanent; natural fruit colors will wash out.
Dilute Mineral Acids redden natural fruit colors, turning yellow those containing aniline coloring.
Half a volume of Nitric Acid instantly turns an artificial color yellow.
Carbonate of Potassium reddens artificial colorings, but has no effect on natural.
Subacetate of Lead precipitates red with Fuschin, and green with natural fruit juices.