Question

Why is the drop of sample placed at the centre and allowed to dry before introducing it into the solvent?

Answer 1

During Chromatography, to ensure the flow of direction occured due to the action of capillary forces on the migrating solvent, a drop of sample placed at the centre and allowed to dry before introducing it into the solvent.

Explanation :

• If the movement of the sample in its mobile phase runs in upward direction, It is determined as ascending development. Generally, this upward movement occurs due to the action of capillary forces on the sample.

• If the movement of the sample in its mobile phase runs in downward direction, It is determined as descending development. In such cases, the paper is put into the trough and then releases into the solvent. The movement of liquid occus due to both gravitational pull and capillary forces, here.

• In rare and special cases, the movement of the sample in its mobile phase runs outward the sample point. Such a case is said to be the radical or disc development.

• Once the paper is released into the solvent till some margin, the rate of movement of the solvent flow becomes slower with increasing height.

Learn more :

1) Chromatography and paper chromatography

https://brainly.in/question/1078955

2) What is chromatography?

https://brainly.in/question/932004