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The Dragendorff Reagent

Johann Georg Noel Dragendorff VIAF: 14888964 (August 8, 1836 – April 7, 1898) was a German pharmacist and chemist born in Rostock.1) 2) 3)

He earned his doctorate in philosophy from the University of Rostock in 1861, and following graduation worked for the Pharmaceutical Society of St. Petersburg. From 1864 to 1894 he was a professor of pharmacy at the University of Dorpat. In 1872 he was awarded an honorary doctorate in medicine from the University of Munich. He was the president of the Estonian Naturalists' Society in 1890–1893.

His name is associated with “Dragendorff's reagent”, which is a solution of potassium bismuth iodide used to ascertain the presence of alkaloids, along with “Dragendorff's test”, a qualitative test formerly used for bile.

RAGENDROFF'S REAGENT is potassium bismuth - iodide solution. This reagent generally gives reddish brown precipitate with alkaloids hence it is used to identify alkaloids.


The Dragendorff's Reagent is used for the detection of Nitrogenous compounds, alkaloids, antiarrhythmic drugs and surfactants and is also good detector for Phenols.4)


There are two methods to prepare this reagent. Each procedure involves preparation of two solutions, viz. Solution A and Solution B. Both Solution A & B are mixed before use.

1st Method:

Solution A: 1.7 g basic bismuth nitrate in 100 ml water/acetic acid (4:1).

Solution B: 40.0 g potassium iodide in 100 ml of water.

Mix reagents together as follows: 5 ml A + 5 ml B + 20 ml acetic acid + 70 ml water.

Spray plates, orange spots develop. Spots intensify if sprayed later with HCl, or 50% water-phosphoric acid. Good for phenols.

2nd Method:

Solution A: 1.7 g basic bismuth nitrate and 20 g tartaric acid in 80 ml of water.

Solution B: 16 g potassium iodide in 40 ml of water.

Procedure for application

Stock Solution: [Stability: stable several weaks in a refrigerator.] mix equal volumes of solutions A and B

Spray with a solution of 10 g tartaric acid, 50 ml water & and 5 ml stock solution.

Selected Bibliography

Linda B. Rubia; Ralph Gomez TLC sensitivity of six modifications of Dragendorff's reagent Journal of Pharmaceutical Sciences 1977 , 66 ,1656-1657

L. Trézl; P. Bakó; L. Fenichel; I. Rusznák Detection of crown ethers by means of dragendorff's reagent Journal of Chromatography A 1983 , 269 , 40-43

Fardous A. Mohamed; Gamal A. Saleh; Salwa R. El-Shaboury; Azza H. Rageh Selective Densitometric Analysis of Cephalosporins Using Dragendorff’s Reagent Chromatographia, 2008 , 68, 365-374

Dipakranjan Mal; Goutam Biswas Detection of organosulphur compounds on thin layers using Dragendorff's reagent Journal of Chromatography A, 1987, 387, 556-558

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named/reagents/the_dragendorff_reagent.txt · Last modified: 2014/12/08 21:29 (external edit)

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