If it is red or brown, the dyed fibre is dried and divided into two parts. One is boiled with bleaching powder. If it is bleached entirely or to a large extent, the dye is cutch. If the bleach has no action, incinerate some of the dyed fibre in an iron crucible and heat the ash on charcoal before the blowpipe. If a globule of lead is formed, we have saturn red. The second portion is boiled with concentrated hydrochloric acid. If there is no action, we have Cologne umber; if there is partial action, we have real umber; if the dye dissolves completely to a yellow solution, we have an ochre; if the solution is colourless instead of yellow, and chlorine is evolved during solution, we have manganese brown. If the colour is yellow or orange, boil with concentrated hydrochloric acid. If we get a green solution and a white residue, we infer chrome yellow or orange. If we get a yellow solution, we boil it with a drop or two of nitric acid and then add some ammonium sulphocyanide. A red colour shows an ochre or Sienna earth. If the colour is green, boil with caustic soda lye. If the fibre turns brown, we have chrome green. If no change takes place, boil with concentrated hydrochloric acid. A yellow solution shows green earth; a red colour logwood plus fustic. If the colour is blue or violet, boil with caustic soda lye. If the fibre turns brown, we have Prussian blue. If no change takes place, boil with concentrated hydrochloric acid. A yellow solution shows smalts. If the colour is destroyed, and the smell of rotten eggs is developed, we have ultramarine. If the colour is black, warm with concentrated hydrochloric acid containing a little tin salt. If the black is unchanged, we have a black pigment. If we get a pink to deep red solution we have logwood black. By means of the tests above detailed at length the group to which the dye belongs is discovered, and often the actual dye itself. Once the group is known it is generally easy, by means of the special reactions given in many books, _e.g._, in Schultz and Julius's "Tabellarische Übersicht," to identify the particular dye. When one has to deal with a single dye and simply desires to determine its group, the following table, due to J. Herzfeld, will suffice. Originally intended for textiles, it will serve, with some modifications here made in it, for the rapid testing of paper. 1.--RED AND REDDISH BROWN DYES.