(b) Apply lemon juice: 1. The violet becomes brighter if it is one of the aniline violets, to be distinguished from each other by applying one part of hydrochloric acid to three parts of water, when it will become violet-blue, changing to red if it is common aniline-violet, but blue changing to a green hue and upon adding plain water to a lilac or pearl gray if it is iodine-violet (Hoffman's). It will also turn from red to yellow in lemon juice. To test for the other three violets: (a) Apply chloride of lime, to be followed by a solution of yellow prussiate of potash: absence of a blue coloration leaves orchil and logwood to be considered. To distinguish between them apply solution of hydrate of lime, whereby a change to gray, followed by complete decoloration indicates logwood, and a change to violet-blue, orchil. The substances utilized with but few exceptions for red ink are the "eosins," possessing different names like erythrosine, as well as different hues. Antecedent to about thirty-five years ago, cochineal (known as "carmine"), madder, Brazil wood and saffron formed the basis of most of the red inks. Make a soap solution adding a small quantity of ammonia, lemon juice, muriate of tin, all in water: 1. No change upon application indicates madder. 2. Any change, the presence of one of the three other reds: (a) thus a complete decoloration with a return of the color indicates saffron; (b) reappearance of the red color though weaker, aniline-red: (c) production of a yellowish red or light yellow color, cochineal or Brazil wood, to be distinguished from each other by the application of concentrated sulphuric acid, when Brazil wood will at once give a bright cherry-red, and cochineal a yellowish orange. No yellow inks are in commercial use. Documents do, however, often contain yellow marks about which information is required as to their origin. As a rule they are iron rust, picric acid, turmeric, fustic, weld, Persian berries or quercitron. In order to recognize the different colors, the presence or absence of iron rust and picric acid must first be determined. Apply a warm sample of a slightly acid solution of yellow prussiate of potash; iron rust will be indicated by a blue coloration. Apply a weak solution of cyanide of potassium; picric acid will yield a blood-red coloration. If picric acid and iron rust are both absent, apply a bit of ordinary wetted soap: 1. It turns reddish-brown and becomes yellow again with hydrochloric acid-- turmeric; 2. It turns quite dark--fustic; 3. It is unaffected--weld, Persian berries or quercitron. To distinguish between these three, apply sulphuric acid, the color of weld will disappear, and of the others remaining apply tin-salt solution, when a change to orange indicates Persian berries, and no change or a very slight one, quercitron.