Users handbook for M series - A&D COMPANY, LIMITED - #3

A&D Company, Limited/Int'l div.

I.What is moisture content?

Moisture content is usually shown as a percentage of water contained in a solid, liquid or vapor material. Where sample is vapor or liquid, it can be in percentage of weight of water contained in its sample's volume and it can be called hygroscopic moisture or humidity. Since moisture content may be classified into various statuses with names to them, evaluation of and dealing with measured data require a special care.

Moisture adhered to a material's surface is called water of adhesion, free water or hygroscopic moisture and moisture adhered to a material with a certain condition such as pressure, temperature, volume etc. is called absorbed water or equilibrium moisture content. Water chemically bonded to a material itself or inside of the material is crystal water or hydrated water while its moisture is bond water or combined water.

REFERENCE

In measurement of moisture content with a moisture analyzer, some materials are measured with a stable moisture content rate and a typical material with such character is Sodium Tartrate Dihydrate. Known by its name it is a well-known material secondarily produced while alcoholic beverage such as wine is made. The material is a hydrate that has hydrate water in crystal and a combined material ( molecular formula : Na₂C₄H₄O2H₂O, rational formula [H₂O.CH(OH)COONa]₂ / molecular mass 230.0823 ) of Sodium Tartrate ( molecular formula : Na₂C₄H₄O₆,rational formula [-CH(OH)COONa]₂ / molecular mass 194.0517 ) and two water molecules ( 2H₂O,molecular mass 36.03056 ). Sodium Tartrate Dihydrate changes into Sodium Tartrate (anhydrate) by releasing the two water molecules with heat energy. Since Sodium Tartrate Dihydrate's melting point is 150C, at room temperature it is stable and does not releases crystal water in its molecules but starts releasing the decomposition of other factors than crystal water. Thus in order to vaporize crystal water selectively when moisture is measured with a moisture analyzer with heating and drying method, it is suffice to say that heating temperature should be between 150C to 200C.Its moisture content rate is logically deemed by the ratio of 2 water molecules, that is (36.03056/ 230.0823) x 100 = 15.66%.

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