MEDICAL AND BIOLOGICAL STAINING TECHNIQUES 



Nitrates 



Solution required: 



Diphenylamine . . . . . . i gm. 



Sulphuric acid, cone. . . • • 75 "il- 



Distilled water . . . . • • 25 ml. 



Add the sulphuric acid cautiously to the water in 

 small portions (about 5 ml.) at intervals in a 250-ml. 

 conical flask, swirling the contents round gently to 

 ensure thorough mixing. 



Do not on any account add the water to the acid as 

 this will result in the acid flying back and causing 

 serious injury to the face and hands , clothing , etc. 



After the diluted acid has cooled somewhat, add 

 the diphenylamine. 



Technique: 



1. Place sections on slides under coverslips. 



2. Place two drops of the diphenylamine solution along one 

 edge of the coverslip. 



Results: 



If nitrates are present a deep blue colour develops as the 

 diphenylamine-sulphuric acid solution seeps under the coverslip 

 and comes into contact with the section. After a few minutes, the 

 section disintegrates and the colour changes to light brown. 



Pectic Substances 



Solution required: 

 A. Ruthenium red, 0-02% aqueous 



Technique: 



1. Stain with the ruthenium red for thirty minutes. 



2. Mount in glycerine on a slide. 



Results: 



Pectic substances are stained red. 



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