Organic Reagents used in Inorganic Analysis

5. 
Dithizone: 
This is diphenyl thiocarbazone which forms coloured precipitates 
with metal like lead, silver, copper, mercury, cadmium. 
Use: It is commonly used to confirm lead with which it forms a red 
colour complex in neutral medium. The most important use of 
reagent is colorimetric determination of lead which forms a red 
colour complex. Zinc also form a complex of same colour and if 
present must be separated by back extraction with aqueous 
potassium thiocyanate. 

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Inorganic Chemistry II (CHEM-363) 
 
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21 
6. 
Pyridine: 
It is a simple 6-membered heterocyclic compound which is colorless liquid 
boiling at 115°C.It is miscible with water in all proportion. 
Use: It is used in precipitate from as ferric hydroxide. It may also be 
used for gravimetric estimation of copper as it forms an insoluble 
complex. While for the estimation of germanium and silicon these 
are first to be converted into germano and silicomolybdates which 
are then precipitated with pyridine.