Volumetric moisture content determination

Essential oil determination results should always be expressed on a moisture-free basis. Therefore, alongside essential oil determination, moisture content determination of the same plant material also should be carried out using a proper glass apparatus (Dean Stark type). The technique involves distillation of the sample with an immiscible solvent (e.g., xylene and toluene) presaturated with water. Water within the plant material is codistilled with the volatile solvent and condensed into a graduated tube where water collects at the bottom of the tube below the solvent line. Solvent continuously returns to the distillation flask. The volumetric moisture content determination apparatus is shown in Fig. 9.2. 

FIGURE 9.2. Volumetric moisture content determination apparatus. 

The moisture content of cmde sulfur is determined by the differential weight of a known sample before and after drying at about 110°C. Acid content is determined by volumetric titration with a standard base. Nonvolatile impurities or ash are determined by burning the sulfur from a known sample and igniting the residue to remove the residual carbon and other volatiles. 

For determination of the total mass-emission rate of SO9, the moisture content and the volumetric flow rate of the exhaust gas stream must also be measured. 

Karl Fischer Titration Moisture content of reference standards is commonly and accurately determined by Karl Fischer (KF) titration. KF titration determines total water content, including both the free water and water of hydration trapped in the crystal structure. Coulometric KF-titration is the most sensitive application of the method and is normally used for the small amounts of water found in reference standards. A volumetric technique is available for samples containing large amounts of water. Interference is a relatively common problem in KF titration and thus, due caution must be exercised in the interpretation of KF results. Reagents have been designed to cope with interfering functional groups.48-50... 

The pilot plant experiments were carried out with various pigments (Table 10.1) dried in a spray dryer with the shock-wave atomizer designed according to the aforementioned procedure (Figure 10.7). Each test was run for 8 hours to obtain a representative sample of about 2000 kg of dry product. The filter cake at an initial moisture content from 50% to 60% wb was dried under optimum conditions determined from laboratory tests, that is, at an inlet air temperature of 170°C and a feed rate of about 120 kg/h. An average evaporation rate for all tests was about 28 kg H20/(m h), which is markedly higher than for currently used spray dryers for which the volumetric evaporation capacity is about 10 kg/(m h). 

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