Wetting bulk powder

Historically, the most common method of drying of pharmaceutical powders has been tray-drying. With this method, wet powder or granulation is placed on paper-lined trays, usually solid or perforated metal, which are then placed directly onto racks in a drying chamber (oven) or onto movable racks, or trucks, that are wheeled into an oven. The heat and low relative vapor pressure of solvent provided by the flow of heated, dry air throughout the chamber provide a driving force for solvent transfer to and subsequent removal from the particle surfaces of the powder. This results in the gradual overall loss of solvent from the bulk powder. 

Moisture content (also water content ) is in principle very simple to measure it is the quantity of water in a unit mass of bulk powder, as a percentage or fraction by mass (or weight). The confusion arises whether the mass of bulk powder includes moisture or not. The moisture content may, therefore, be either on a dry basis (i.e. per unit mass of dry powder) or on a wet basis, the former being more frequently used such as in soil mechanics for example16. 

This description is traditional, and some further comment is in order. The flat region of the type I isotherm has never been observed up to pressures approaching this type typically is observed in chemisorption, at pressures far below P. Types II and III approach the line asymptotically experimentally, such behavior is observed for adsorption on powdered samples, and the approach toward infinite film thickness is actually due to interparticle condensation [36] (see Section X-6B), although such behavior is expected even for adsorption on a flat surface if bulk liquid adsorbate wets the adsorbent. Types FV and V specifically refer to porous solids. There is a need to recognize at least the two additional isotherm types shown in Fig. XVII-8. These are two simple types possible for adsorption on a flat surface for the case where bulk liquid adsorbate rests on the adsorbent with a finite contact angle [37, 38]. 

Bulk Blenders Vlanv of the mixers used for solids blending (Sec, 19) are also suitable for some liquid-solids blending. Ribbon blenders can be used for such tasks as wetting out or coating a powder, When the final paste product is not too fluid, other solids-handling equipment finds frequent use. 

Most dangerous group Black Powder and colloidal propellants, in bulk placed in boxes, and chlorate explosives, not cartridged. Dynamites with attached caps fuses, detonators, nonelectric at electric and Nitroceiiuioses wetted with at least 25% water. Aromatic nitrocompounds, packed in double containers the inner ones from leather, cardboard, heavy paper envelope., while the outer ones nf wood or copper. The fulminates must be transported in vessels filled with water... 

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