STAIN TECHNIQUE 65 



worked into a paste in a casserole with 5 ml. of 35 per cent sodium 

 hydroxide, to which is added slowly 45 ml. of hot water, and then, 

 with continuous stirring, ^ gram of sodium hydrosulfite powder. 

 The vat may be colorless or it may be different from the original 

 dye; Indigo changes from blue to yellow-green in the vat. After 

 five to ten minutes at 60° C, the material is taken out of the stain 

 and rinsed in warm water. The stained object should be the same 

 color as the original dye. Pigments obtained from bright orange 

 or red dyes disappear from blue-green algae soon after the algae 

 are placed in glycerin, but jade green, violet, and indigo are fast 

 colors. 



1180. Indigo Carmine, Indigotine is a direct dye similar in 

 color to Niagara Sky Blue 6B ; ^ gram in 95 ml. of distilled water, 

 5 ml. of 5 per cent sodium sulfate, and ^ ml. of acetic acid. The 

 stain gives an indigo on sections of animal tissues within ten min- 

 utes, on plant tissues in one to 24 hours. An important property 

 of the dye is its selectivity in staining nuclei, and its delicate shading 

 of embryonic or plant meristematic tissues. These minute differ- 

 ences in muscular, vascular, nervous, and digestive tissues are evi- 

 dent after a triple or quadruple stain including : ( 1 ) a mixture of 

 nine parts Sun Yellow and one part Acid Fuchsine for ten minutes 

 followed by Indigo Carmine for five to ten minutes; or (2) a mix- 

 ture of ten parts Sun Yellow, five parts Orange II, and one part 

 Acid Fuchsine, followed by Indigo Carmine. 



