Question

Make a lactometer with ball point refill.what would you do to make the refill stand vertically straight? to make a refil stand

Answer 1

Actually, lactometer is the instrument used to check the purity of milk on the density basis.
In order to make a lactometer from ball point refill first of all take empty ball point refill( Refill should be made of metal from the point end).
Then take a boiling tube filled with water and pour the refill in to the water.
After that insert the small piece of erasure in the refill so that so that refill stand in water.
Now , note the point  of refill ( which is standing above water level).

Now clean the tube and again filled it with milk, and again pour refill in the water and note the point again but of milk surface.

after that you can repeat the procedure with milk water. 
Note and compare the value would give you the estimate of the milk purity.