This document discusses standard, saturated, and supersaturated solutions, defining standard solutions as those with known concentrations, and detailing their preparation methods. It categorizes standard solutions into primary and secondary types based on purity and stability, and outlines steps for preparing stock and working solutions. Saturated solutions are described as those holding maximum solute under given conditions, while supersaturated solutions contain more solute than possible at equilibrium, created under specific conditions of temperature and cooling.

1. Standard, saturated and
supersaturated solutions
Karthik G Kamath K
Associate Professor
Department of Biochemistry

2. Standard Solution
• Solution containing an accurately known concentration
• Dissolving a known mass into a solvent of precise volume
• Or diluting solution of known concentration with more solvent
• Used for determination of solutions with unknown concentration
– titration

3. Uses of standard solution
Titration
Determination of concentration using a calibration curve

4. Types of standard solutions
• Analytical standards can be categorised into
• Primary standards – compounds of known stoichiometry, high
purity, & high stability
• Prepared using accurately weighing a known quantity of solute
followed by dilution to a precise volume

5. Types of standard solutions
• Secondary standards – compounds with concentration
determined by a primary standard
• They do not satisfy the requirements of primary standards

6. Types of standard solutions
• Based on use and storage standard solutions can be of
• Stock standard solutions – concentrated versions of standard
solutions
• Can be used on its own
• Or part of a mixture of complex solutions

7. Types of standard solutions
Preparation of stock standard
1. Calculation – calculate the mass to be weighed for the required
strength of the solution
2. Weigh – accurately the amount of solute required
3. Dissolve – the solute in precise volume of the solvent

8. Types of standard solutions
4. Adjust the pH – if required
5. Adjust the vol – to the required, after the pH is set
6. Label and store

9. Types of standard solutions
• Working standard solutions
• Prepared from stock solution
• By diluting small volume of stock using the diluent

10. Types of standard solutions
Preparation of working standard
1. Calculation – calculate the volume of the stock standard for the
required strength of the working standard solution
2. Dilute – the stock solution in precise volume of the diluent
3. Adjust the pH – if required
4. Adjust the vol – to the required, after the pH is set
5. Label and store

11. Saturated solution
• Is a solution that contains the maximum amount of solute that
can be dissolved under the condition at which the solution exists
• Undissolved solute lies at the bottom
• A saturated solution is a solution that is in equilibrium with
respect to a given dissolved substance

12. Preparation
• It is prepared by continuously adding solute to the solution until a
stage is reached where the solute appears as a solid precipitate or
as crystals to form a highly saturated solution.
• Consider the process of adding table sugar to a container of
water.
• Initially, the added sugar dissolves as the solution is stirred.

13. • Finally, as more sugar has added a point is reached where no
amount of stirring will cause the added sugar to dissolve.
• The last added sugar remains as a solid on the bottom of the
container, the solution is saturated

14. Supersaturated solution
• A solution contains more dissolved substance than a saturated
solution does
• A supersaturated solution is a solution that contains more than
the maximum amount of solute that is capable of being dissolved
at a given temperature

15. Preparation
• Special conditions need to be met in order to generate a supersaturated
solution.
• The more heat is added to a system, the more soluble a substance
becomes. Therefore, at high temperatures, more solute can be dissolved
than at lower temperatures.
• If this solution were to be suddenly cooled at a rate faster than the rate of
precipitation, the solution will become supersaturated until the solute
precipitates to the temperature-determined saturation point.

16. • The precipitation or crystallization of the solute takes longer than
the actual cooling time because the molecules need to meet up
and form the precipitate without being knocked apart by the
solvent.
• Thus, the larger the molecule, the longer the solute will take to
crystallize due to the principles of Brownian motion.