Question

Brunt sugar solution is added in the limit test lead​

Answer 1

Answer:

Lead is a most undesirable impurity in medical compounds and comes through use of sulphuric acid, lead lined apparatus and glass bottles use for storage of chemicals.

Principle:

Limit test of lead is based on the reaction of lead and diphenyl thiocabazone (dithizone) in alkaline solution to form lead dithizone complex which is read in color.

Dithizone is green in color in chloroform and lead-dithizone complex is violet in color, so the resulting color at the end of process is red.

Procedure:

Test sample Standard compound

A known quantity of sample solution is transferred in a separating funnel A standard lead solution is prepared equivalent to the amount of lead permitted in the sample under examination

Add 6ml of ammonium citrate Add 6ml of ammonium citrate

Add 2 ml of potassium cyanide and 2 ml of hydroxylamine hydrochloride Add 2 ml of potassium cyanide and 2 ml of hydroxylamine hydrochloride

Add 2 drops of phenol red Add 2 drops of phenol red

Make solution alkaline by adding ammonia solution. Make solution alkaline by adding ammonia solution.

Extract with 5 ml of dithizone until it becomes green Extract with 5 ml of dithizone until it becomes green

Combine dithizone extracts are shaken for 30 mins with 30 ml of nitric acid and the chloroform layer is discarded Combine dithizone extracts are shaken for 30 mins with 30 ml of nitric acid and the chloroform layer is discarded

To the acid solution add 5 ml of standard dithizone solution To the acid solution add 5 ml of standard dithizone solution

Add 4 ml of ammonium cyanide Add 4 ml of ammonium cyanide

Shake for 30 mins Shake for 30 mins

Observe the color Observe