Question

How to make lactometer with ball point refill and it should stand vertically straight

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.

Answer 2

Lactometer is an instrument which is utilized to test the immaculateness of milk. 
TO make a lactometer with ballpoint refill, one should follow the following steps.

1.Take a vacant ball pen refill. 2. Refill ought to have a metal point at the base. 
3.Take a bubbling tube and fill it with water. 
4.Put the refill in the water with a metallic point. 
5.To make the refill to remain in the water, embed a little eraser piece in the refill at the inside. 
6.Mark the point with marker up to which the refill is over the water. 
7. Now, purge the bubbling tube with water and fill it with milk. 8.Again put the refill in milk and mark the point which demonstrates the part which is over the surface of the milk. 9.Further, we can include, milk water blend in the bubbling tube and rehash a similar stage 8. 
10. we would now be able to analyze and test whether water is added to milk or not.