Melt Point vs. Titer Point

Industry expert Tony O’Lenick explores the difference between melt point and titer point.

Both melt point and titer point refer to the temperature at which solid materials become liquid; however, the difference lies in the way in which they become liquid.

Melt point: defines the melt point as, “the temperature at which a solid changes to a liquid. For pure substances, the melting or fusion process occurs at a single temperature--the temperature rise with the addition of heat being arrested until melting is complete. Under standard atmospheric pressure, different pure crystalline solids will each melt at a different specific temperature; thus melting point is a characteristic of a substance and can be used to identify it. When heat is applied continuously and in sufficient quantity to such solids, the temperature rises steadily until it reaches the point at which liquefaction occurs. Here the rise ceases and no further change in temperature is observed until all of the substance has been converted to liquid.”

Melt points essentially refer to pure substances. One might recall the endless separations conducted in the organic chemistry lab, using solvent in a separatory funnel to purify compounds. With increasing purity, the melting range narrows until hopefully one value is obtained. It is this value--melt point--that one finds in standard databases. In the commercial world, however, many materials of interest are not pure but are oligomeric mixtures, which do not give clean, narrow melting ranges.

Titer point (or cloud point): Titer point measures not a range of temperatures, but the temperature at which the lowest melting material first becomes hazy. This is important for materials that are not one specific structure, but a mixture of related structures. Such materials, for example, are esters that can have a wide range of molecular weight species present (C8-C22). These different components often solidify at different temperatures. As a product is cooled, often there will be a cloudiness that forms as the least soluble material begins to crystallize. This cloudiness is called the cloud point or titer point. and should not be confused with the high cloud point observed when aqueous solutions of surfactants are heated.

The fact that materials have a titer point rather than a distinct melt point can be beneficial to the cosmetic formulator. The range of materials present in a raw material that account for the titer point can have very different properties when applied to the skin. Higher molecular weight esters, for example, can have a greater lubricity on the skin while lower molecular weight esters can improve spreadability. The combination in one product can result in a liquid product that has the lubricity and spreadability. Formulators familiar with these differences will use them wisely in making products.

1. Titer Point Method,  
2. Melting Point Apparatus,
3. Pictures of titer points,
4. Separatory Method,  

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