"Natural colors impart to the wool, when treated in this way, only a dull pinkish-brown color, quite different from the brilliant color of the artificial dye. In order to be absolutely certain, however, it is best to take the dyed wool and boil it with about a table-spoonful of ordinary household ammonia in half a pint of water. After boiling for five minutes, remove the wool, and if the ammonia is colored add to it a third of a cupful of vinegar, immerse it in a second piece of the white woolen cloth and boil it as before. Any color that is imparted to the second piece of cloth is the analine dye, which was dissolved off by the ammonia. The natural color would not be removed from the first cloth by the ammonia, hence would not dye on the second piece. The coloring can be boiled out of sausages and dyed on wool in the same way".
"Another interesting way of showing the presence of these dyes, especially in beverages, is to dye them on gelatine. Dissolve one part of gelatine in ten parts of boiling water and pour it into a deep pan to harden. When it is cold, by means of a sharp knife cut it into inch cubes. Place one of these cubes into the suspected liquid and allow it to remain for twenty-four hours, then wash it slightly with cold water and cut through it with a knife. If the color is a natural one it will lightly tinge the outer surface of the cube, but will not penetrate far below the surface, so that the inner portions will be largely free from color. Nearly all of the coal-tar dyes, cochineal and similar colors, will be found to permeate the jelly cube, often to the center.
"One advantage of the dyeing on cloth, however, is that the sample can be preserved as evidence. Nothing is better than ocular proof to convince the average person".
Several other tests for food adulteration have been given under the special foods or in other papers of this series. (See also Bulletin No. 100. Sonic Forms of Food Adulteration and Simple Methods for Their Detection. Price 10 cents, of the Supt. of Documents, Washington, D. C).