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Eutectic mixtures and geometric dilutions

The term eutectic was first used by physicist and chemist Frederick Guthrie in 1884.

Eutectic mixtures

The term eutectic was first used by physicist and chemist Frederick Guthrie in 1884. When a homogeneous mixture of substances melts or solidifies at a single temperature, it means that the melting point of each component is lower than the temperature of the entire system.

The eutectic state can also be defined as a state when a mixture of substances is melted or frozen at a temperature that was smaller than the melting point of each of the individual components or a mixture of them. As such, it is known as the eutectic temperature, as it is the lowest melting temperature that can be reached by mixing all component species.

After cooling a mixture of random liquid substances, one part begins to detach in solid form as the temperature is lowered, and continues to do so as lower temperatures are reached. Upon dividing this portion, the resulting liquid becomes increasingly rich in one constituent, until the structure of the liquid approaches a point where all elements dissolve into an intimate mixture of solids. A eutectic structure solidifies at a temperature, and the temperature is the eutectic temperature. Since the melting temperatures of their constituents are different for components with different lattices, non-eutectic ratios would have different melting temperatures for their constituents. However, a non-eutectic aggregate would solidify as it cooled, solidifying at various temperatures until it solidified completely.

In chemical chemistry, eutectic mixtures are defined as mixtures of derivatives that, rather than reacting and creating new compounds, inhibit their crystallization at certain ratios, producing melting points lower than those of the constituents individually. There are multiple ways to create eutectic mixtures within the pharmaceutical industry, including combining APIs, APIs, and excipients, or excipients, allowing for a variety of pharmaceutical applications.

Eutectic mixtures are usually created by the following factors:
  1. Liquid components must be miscible with liquid components and solid components must be miscible with solid components.
  2. The contact-induced melting point depression requires close contact between the eutectic forming materials.
  3. An interaction between two chemical groups that results in a physical bond, such as intermolecular hydrogen bonds.
  4. A modified version of VantHoff's law.

Eutectic temperature

The eutectic temperature remains the lowest melting temperature irrespective of the compositional ratios present in a eutectoid. When a superlattice reaches this temperature, all of the components will evaporate, and the entire eutectic structure will melt into a jelly. As opposed to a eutectic mixture, in a non-eutectic mixture, each portion solidifies into a lattice at its temperature before the whole mix solidifies.

Eutectic composition

Eutectics are melt-and-freeze compositions made up of at least two elements of the same melting and freezing properties. The crystallization process creates a mixture of all the components, allowing the product to behave as a unit. (Lane, 1989) The materials form a dense crystal network and melt together simultaneously, with no distinction. Eutectics are chemical mixtures of organic and/or inorganic substances. The result is that organic-organic blends, inorganic-organic blends, and organic-inorganic blends can be made.

Geometric Dilutions

In the pharmaceutical industry, geometric dilution involves thoroughly mixing a small amount of drug with the appropriate amount of a solvent, which thins or binds it. By doing so, the resultant compound is evenly distributed with the drug.

As with any compound, the method of preparation varies with the compound, its form (such as an ointment or tablet), and the substances used. The UNC Eshelman School of Pharmacy explains that geometric dilution methods include triturating powders and mixing powders into ointments, as well as the liquid aliquot method, which combines fluids to produce a solution.

When a substance is triturated, it is reduced to particle size by grinding equal parts of both substances in small batches and then adding the same amount of each substance to the other and re-mixing until both substances have been thoroughly mixed. An aliquot is a method for dissolving a drug in an appropriate solvent to obtain the desired volume. Most commonly, it is water or alcohol. To make up the total prescription volume, aliquots of the concentrated drug solution are added to an amount of solution larger than that.
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Ankur Choudhary is India's first professional pharmaceutical blogger, author and founder of, a widely-read pharmaceutical blog since 2008. Sign-up for the free email updates for your daily dose of pharmaceutical tips.
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