Answer: Density
Step-by-step explanation:
Density is the parameter which is used for comparision of two doubted to be similar pieces of the glasses in the columns where a specific volume of liquids bromoform and bromobenzene are used. The two glasswares (graduated cylinders) are used in this process along with the liquids. The level at which the glass pieces in the column settles that represent their density. If two pieces of glass are from same source then they will settle at the same level in the column. This method is known as density gradient method.