Osmotic Pressure

Introduction

The osmotic pressure is the minimum pressure required to prevent a solution’s pure solvent from flowing inward through a semipermeable barrier.

It can also be described as a measurement of a solution’s proclivity to absorb a pure solvent via osmosis. The highest osmotic pressure that could develop in a solution if it were removed from its pure solvent by a semipermeable membrane is known as potential osmotic pressure.

Osmosis happens when two solutions with different quantities of solute are separated by a selectively permeable membrane. Solvent molecules flow over the membrane preferentially from a low-concentration solution to a solution with increasing solute concentration. The transfer of solvent molecules will continue until equilibrium is established.

Osmotic Pressure

When a semipermeable membrane separates a solution from pure water, osmotic pressure is the pressure that has to be applied to the solution side to cease fluid movement.

Jacobus Henricus van ‘t Hoff, a Dutch-born chemist, demonstrated in 1886 that if the solute is dilute enough that its partial vapour pressure above the solution obeys Henry’s law (i.e., is proportional to its concentration in the solution), then osmotic pressure varies with concentration and temperature like that of a gas occupying the same volume.

This relationship led to formulae for estimating the molecular weights of solutes in dilute solutions based on the solvent’s freezing, boiling, and vapour pressure.

It is calculated using the following formula:

π = iCRT

Where,

π = osmotic pressure

i =  van’t Hoff index

C = molar concentration of the solute 

R = ideal gas constant

T = temperature in Kelvin

Solvent molecules pass over a semipermeable membrane from one region to another where the concentration of the solute is low to a region where the concentration of the solute is high, eventually establishing equilibrium on both sides and resulting in the same concentration on both sides, is referred to as osmosis. Diffusion is a specific case of osmosis.

It is the mechanism by which a solvent flows in the opposite direction of natural osmosis over a semipermeable membrane. The water filtration method known as reverse osmosis removes ions, undesirable compounds, and bigger particles from drinking water.

Systems That are Regulated by Osmotic Pressure: 

A semipermeable membrane is placed around the tablet, particle, or drug solution in osmotic pressure controlled systems, allowing water to enter the tablet and drug solution to be pumped out through the small delivery hole in the tablet core. There are two types of osmotic pressure-regulated systems described in the literature. The drug is held in a flexible bag surrounded by an osmotic core in type 1, whereas the drug is held in a flexible bag surrounded by an osmotic core in type 2. It is feasible to design an osmotic system to distribute various drugs at a predetermined rate by optimising the formulation and processing variables.

Osmosis is a process in which fluid flows from a lower concentration to a higher concentration across a semipermeable membrane that allows only liquid to pass through. The medicine is coated with a semipermeable membrane, and a laser beam is used to create a hole in one end of the tablet. The drug solution is pumped out of the aperture and released into the stomach environment as the gastric fluid seeps through the membrane, solubilised the drug, and increases the internal pressure, causing the medication solution to be pumped out of the aperture and released into the gastric environment. If there is an excess of medicine inside the pill, the delivery rate remains constant. When the concentration falls below the saturation point, however, it drops to zero.

Osmosis and Osmotic Pressure: 

Osmosis is the natural flow or diffusion of water or other solvents through a semipermeable barrier (one that prevents the passage of dissolved compounds, such as solutes).

Wilhelm Pfeffer, a German plant physiologist, was the first to explore this vital biological process. Previously, less detailed studies of leaky membranes (e.g., animal bladders) and the transit of water and escape compounds in opposite directions across them had been done. Thomas Graham, a British physicist, created the term osmose in 1854. (now osmosis).

The osmotic pressure of a solution is intimately linked to various other features of the solution, known as colligative qualities. Dissolving solutes in a solution causes freezing point depression, boiling point elevation, and vapour pressure depression, among other effects. Rather than direct osmotic pressure measurements, vapour pressure depression of freezing point depression is frequently used to estimate osmolarity. The concentration required to witness these phenomena is referred to as osmolarity.

Because its vapour pressure is lower than that of the water, a solution placed in a sealed container with a source of clean water will gain water. The semipermeable membrane in this circumstance is the intervening air between the two surfaces, which is formally identical to osmosis. Because osmotic pressure and vapour pressure depression are essentially the same processes, they are perfect forecasters of each other.

Osmotic Pressure in Plants

A discrepancy in the quantities of solutes between solutions separated by a semi-permeable barrier causes hydrostatic pressure.

Water potential, or the tendency for water to move from one place to another, is reduced by osmotic pressure. It is therefore required in plant cells for turgidity and support.

Osmotic pressure can build up inside a cell when water enters through osmosis. If a cell has a cell wall, it helps to keep the cell’s water balance in check. In many plants, osmotic pressure is the primary source of support. The turgor pressure forced against the cell wall by the osmotic entry of water into a hypotonic plant cell rises until it prevents more water from entering the cell. At this point, the plant cell is turgid.

Osmosis can be extremely destructive to organisms, particularly those without cell walls. 

The cells of a saltwater fish (whose cells are isotonic with seawater) will absorb extra water, lyse, and die if they are placed in freshwater.

The usage of table salt to kill slugs and snails is another example of a detrimental osmotic impact.

Example of Osmosis: 

Osmosis is the process through which water is absorbed from the earth. Water flows into the roots because the concentration of plant roots is higher than soil.

The passage of water inside the cells causes the fingers to become pruney when submerged for an extended period.

Osmosis is a vital process in the lives of plants, animals, and humans. Water absorption from the intestines to the blood in animal cells is aided by osmosis.

Example : Raisins swell when placed in normal water. If you put a raisin into pure water, it swells up over time. This happens because raisin contains a higher concentration of sugar and other solutes than water, so water moves into the raisin cells by osmosis.

Conclusion 

Osmotic Solutions:

• Isotonic solution – The concentration of solutes within and outside the cell is equal to an isotonic solution.
• Hypotonic solution – The concentration of solutes inside the cell is higher than outside, resulting in a hypotonic solution.

• Hypertonic solution – The concentration of solutes outside the cell is higher than inside the cell in a hypertonic solution.

Types of Osmosis:

• Endosmosis – When a material is submerged in a hypotonic solution, the solvent molecules enter the cell, causing it to become turgid

or de-plasmolyzed. This is referred to as endosmosis.

• Exosmosis – When a material is placed in a hypertonic solution, the solvent molecules escape, the cell becomes flaccid or plasmolysed as a result. This procedure is known as exosmosis.

Controlling osmosis is one way the body keeps water. When the body is dehydrated, the brain tells the kidneys to concentrate urine to retain more water. Antidiuretic hormone (ADH) is a hormone produced by the brain and transported to the kidneys via circulation. A network of tubes that runs through the kidneys is known as the collecting ducts. Water is generally impermeable to the collecting ducts; thus if water is in the collecting duct, it is on its way to the bladder. ADH, on the other hand, causes water channels to open in the walls of the collecting ducts. Water that would otherwise become urine can now flow out of the collecting duct and back into the bloodstream.