To the aqueous solution of a slat taken in a tube, a feq drops of blue litums solution were added. Ammonia solution was added dropwise to the red solution formed till it regained its blue colour. The solution was then heate3d for sometime and the tube was left undisturbed. A blue mass was seen floating in colourless solution. How will you acount for this ?

Explanation

The aqueous salt solution appears to be that of aluminium , may be aluminium chloride. When ammonia solution was added to it, a gelationous white precipitate of aluminium hydroxide was formed.
`AlCl_(3) +3NH_(4)OH to underset(("white ppt.white ppt.))(Al(OH)_(3))+3NH_(4)Cl`
The particles of blue day present in the litmus solution were adsorbed on the surface of `Al(OH)_(3)` which also acquired blue colour. Thus, a blue precipitate or mass was seen floating over the colourless solution. This is known as Lake test for aluminium.