STAIN TECHNIQUE 67 



in 20 per cent alcohol. The alum stain yields lavender or fuchsia 

 with aluminum, tin, or copper mordants; blue-black to black with 

 uranium or iron salts. The alcohol added to the stain serves as a 

 preservative. 



1242. Litmus, Archil, Orcein is a dye extracted from different 

 lichens. Its principal value is that of an indicator. 



1243. Brazilin, Brazil Wood is an acid mordant dye, light 5. 

 The tropical redwood Caesalpinia, family Leguminosae, contains 

 Brazilin which is soluble in water or alcohol, and is changed on oxi- 

 dation to a red solution of Brazilein. Plant tissues are stained car- 

 mine to dull brown but the color is of low fastness. 



1246. Haematoxylin, Hematein is an acid mordant dye, light 

 2 to 4. The dye is obtained from the wood of Haematoxylon cam- 

 pechianum, family Leguminosae, indigenous to Mexico and Central 

 America but cultivated in the West Indies. When freshly cut the 

 wood is colorless ; upon exposure to air, the surface of the wood be- 

 comes reddish brown with the development of Haematoxylin from 

 a glucoside. After chipping the wood, the dye is extracted with 

 boiling water in open pans or with steam under pressure in closed 

 vessels. The extract is concentrated to a liquor or a solid. On 

 further treatment, the crude product yields the light brown crystals 

 of Haematoxylin. 



The fastness of Haematoxylin differs with (1) the various 

 metallic salts used as mordants, (2) the kind of staining solution, 

 and (3) the temperature of application. The color obtained with 

 iron Haematoxylin has a fastness of 3 to 4 ; of alum Haematoxylin, 

 3. By using iron alum as a mordant and the stain ripened in dilute 

 alcohol, the color developed at 50° C. has a fastness of 2, almost 

 the equal of the best coal-tar dyes. 



Directions for making the solution as originally given by J. 

 Delafield in Zeit. Wiss. Mik.2: 288 (1885) are: "To make 600 cc 

 of the solution, take 400 cc saturated aqueous solution of ammonium 

 alum and add to this 4 grams of crystallized Haematoyxlin dis- 

 solved in 25 cc strong alcohol. This at first produces a light violet 

 or sometimes a dirty red color, but on exposure to the light in an 

 unstoppered bottle the color deepens and a light precipitate forms. 



