So they can predict what happens next
Answer:
Specific gravity of mercury is 13.56 and it is an unit-less quantity.
Explanation:
Mass of the mercury = m = 607.0 lb = 275330.344 g
1 lb = 453.592 g
Volume of the mercury = v = 

Density of the mercury = d=
d = 13.56 g/mL
Specific gravity of substance = Density of substance ÷ Density of water

Specific gravity of mercury :
(unit-less quantity)
The answer to this question would be: resistance
When a patient developing a resistance to a certain drug, the same amount of doses will not exert the same effect as before. The effect will be lower, thus the doctor will need to increase the dose to increase the effect
It is their properties. it is made up naturally due to the ions