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SAPONIFICATION — This is what occurs when fats or oils such as tallow, coconut oil, vegetable oils, and lard are reacted with caustic soda or caustic potash and change form to become soap. Depending on the type of soap to be made, the reaction may take anywhere from a couple of hours to several days at temperatures ranging from 180° F (83° Celsius) to boiling (212°F or 100° C). PICKLING — This effect is produced when metals are immersed in acid solutions which attack them. The process of pickling refers to the removal of heat scale, discoloration and rust from steel by acids, mainly (10% plus or minus a few percent) at temperatures anywhere from 120°F to 180° F./49°C to 83°C. Muriatic acid is used extensively on lesser scaled steels and rusted parts. This acid is used at room temperature at about 20% to 40%. Heat is not used with this acid because of the fuming nature of this acid especially at elevated temperatures. Inhibitors are often recommended to prevent attack on the base metal and to reduce consumption of the acid. Care must be used in adding inhibitors as too much can slow down considerably the descaling or derusting operation. ETCHING — This is the phenomenon 'resulting from the attack of chemicals on base metals. which in effect is an actual removal or dissolving of the surface itself. The surface of the metal will show up as a matte or satin finish caused by tiny pits in the metal. Etching of aluminum is accomplished with caustic solutions, while copper alloys are treated with Nitric, Chromic, and sulfuric acid solutions.,
BRIGHT-DIPPING — Actually, this is another form of pickling in that an acidic solution is used to remove oxides from the surface. On zinc plated steel, acid formulations made up of Nitric acid and chromate salts serve to polish the plated surface by removing the high spots.
DYNES — This is an extremely minute measurement of force;100,000 Dynes= 0.224 Ibs of force. Its application as applied to cleaning is its use as a measurement of surface tension. To measure surface tension, a ring made of extremely fine platinum wire (which is attached horizontally to a delicate measuring instrument) is lowered or pushed through the surface of a water solution of a chemical compound. The amount of force it takes to pull the ring back through the solution and detach it from the surface is measured by the instrument in terms of so many Dynes per centimetre of solution surface. Distilled or de-ionized water has a surface tension of 72 Dynes, while many cleaners will lower the tension to as low as 26 Dynes per square centimetre.
INTERFACIAL TENSION — This term, on the other hand, is used to describe the difference (if any) between the surface tensions of two different substances. For instance, because the surface tensions of oil and water are so far apart they actually repel each other. This naturally means that they will not mix. However, when a wetting agent of proper choice is added to one or the other it intersperses itself between the molecules of each, reducing considerably the surface tension of each to the point where the two will mix, producing a condition known as an emulsion. Neither molecule is recognizable as to their original form.
SEQUESTERING and/or CHELATING — Certain chemicals have the property of being able to 'tie-up' metallic ions in solution, in effect, inactivating them by locking them into a tightly bound ring structure. Examples of sequestering agents are: Calgon, Tri and Tetra Polyphosphates, sugar complexes such as Gluconates, Citrates. Chelating agents are of the family of EDTA compounds, the Ethylene Diamine Tetraacetic acid type. They are known under the trade name as Versene. Without chelating or sequestering salts in cleaning formulations, metals and salts in the water form insoluble scales on the sides.and bottoms of tanks and on heating coils. This scale is hard, and difficult remove.
SURFACE TENSION — This describes a condition on the surface of the water (a kind of skin effect) which makes it more repellent to foreign substances than to the water molecules beneath the surface. All molecules of any given substance such as water, have an equal attraction for each other. Underneath the surface of a water solution all molecules are attracting each other from all directions with equal force. At the surface, however, a molecule is only being attracted from the sides and below, not from above. This unequal pulling effect actually serves to increase the attraction of the molecules for each other right at the surface only, creating what is known as surface tension. The term ‘wetting agent' is usually applied to any chemical such as detergents which lower this surface tension, making the solution or water wetter. The attraction between the water molecules has been reduced by merely interspersing mol-ecules of detergent between them. This reduces the the tension or attract-ion, not only at the surface but also throughout the solution. The tension at the surface however is more obvious and easily measured and that is why wetting is discussed in terms of surface tension.
