Question

washing soda looses its crystalline structure quickly give reasons

Answer 1

Washing soda is an efflorescent substance. This is it loses its water of crystallisation when it comes in contact with the atmosphere.
For this reason it loses its crystalline structure.
Hope it helps.

Answer 2

Wasjing soda (hydrated sodium sulphate solution) is a deliquesent substance.  A deliquesent substance loses its crystalline structure like washing soda (NA2SO4.7H20) because it absorbs atmospheric moisture on exposure to it and dissolves in it. Hence washing soda loses crystalline structure....................