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Example of saponification reaction of a triglyceride molecule (left) with potassium hydroxide (KOH) yielding glycerol (purple) and salts of fatty acids ().. Saponification value or saponification number (SV or SN) represents the number of milligrams of potassium hydroxide (KOH) or sodium hydroxide (NaOH) required to saponify one gram of fat under the conditions specified.
Saponification is a process of cleaving esters into carboxylate salts and alcohols by the action of aqueous alkali. Typically aqueous sodium hydroxide solutions are used. [1] [2] It is an important type of alkaline hydrolysis. When the carboxylate is long chain, its salt is called a soap. The saponification of ethyl acetate gives sodium acetate ...
The classical Stefan problem aims to describe the evolution of the boundary between two phases of a material undergoing a phase change, for example the melting of a solid, such as ice to water. This is accomplished by solving heat equations in both regions, subject to given boundary and initial conditions.
Liquid water and ice, for example, form a frigorific mixture at 0 °C or 32 °F. This mixture was once used to define 0 °C. That temperature is now defined as the triple point of Water with well-defined isotope ratios. A mixture of ammonium chloride, water, and ice form a
The problem with matching the (large) magnitude of the water-ice p-V gradient above the triple point boundary with the magnitudes of prevailing temperature and pressure in the case of the ice skating context applies equally in the context of the classic lab experiment with a copper wire cutting through an 10cm ice block with say a 28 swg wire.
A bath of ice and water will maintain a temperature 0 °C, since the melting point of water is 0 °C. However, adding a salt such as sodium chloride will lower the temperature through the property of freezing-point depression. Although the exact temperature can be hard to control, the weight ratio of salt to ice influences the temperature:
In the above equation, T F is the normal freezing point of the pure solvent (273 K for water, for example); a liq is the activity of the solvent in the solution (water activity for aqueous solution); ΔH fus T F is the enthalpy change of fusion of the pure solvent at T F, which is 333.6 J/g for water at 273 K; ΔC fus p is the difference ...
Salt compounds dissociate in aqueous solutions. This property is exploited in the process of salting out. When the salt concentration is increased, some of the water molecules are attracted by the salt ions, which decreases the number of water molecules available to interact with the charged part of the protein. [3]