Question

It is advisable to prepare Lassaigne’s extract in distilled water. Why?

Answer 1

The Lassaignes’s extract is usually used for testing any organic compound to find out if the compound contains any halogens or nitrogen or sulphur.  

In tap water, there are some chloride ions present. So, if we use it to prepare the extract, then whatever organic compound we test using the extract, it will always show the presence of chlorine even if the organic compound does not have any halogen in it.  

Hence the Lassaigne’s extract should be prepared using distilled water and not tap water.