Dry cells

Dry bead process Dry-cell batteries Dry chemistry Dry-cleaning Dry cleaning fastness Dry-cleaning fluid Dry-cleaning solvent Dryers... 

Ammonium Chloride. Most ammonium chloride [12125-02-9], NH Cl, is used as rice paddy fertilizer small amounts are used in dry cells and as fluxing agents (see Ammonium COMPOUNDS). 

Uses and Economic Aspects. Magnesium bromide is used in medicine as a sedative in treatment of nervous disorders, in electrolyte paste for magnesium dry cells, and as a reagent in organic synthesis reactions. The price of magnesium bromide hexahydrate in January 1995 was 5.51/kg (33). 

Red mercuric oxide, identical chemically to the yellow form, is somewhat less reactive and more expensive to produce. An important use is ia the Ruben-MaHory dry cell, where it is mixed with graphite to act as a depolarizer (see Batteries). The overall cell reaction is as follows ... 

Mmerican National Standard Specification for Dry Cells and Batteries, ANSI C18.1-1979, American National Standards Institute, Inc., New York, May 1979. 

Electrical Uses. Dry cells (see Batteries, primary cells) use graphite to render the nonconductive pyrolusite (Mn02) conductive through intimate admixture. The degree of graphitization is a factor in that graphites with the same carbon content and from the same locaUty give different results. 

Galvanic cells in which stored chemicals can be reacted on demand to produce an electric current are termed primaiy cells. The discharging reac tion is irreversible and the contents, once exhausted, must be replaced or the cell discarded. Examples are the dry cells that activate small appliances. In some galvanic cells (called secondaiy cells), however, the reaction is reversible that is, application of an elec trical potential across the electrodes in the opposite direc tion will restore the reactants to their high-enthalpy state. Examples are rechargeable batteries for household appliances, automobiles, and many industrial applications. Electrolytic cells are the reactors upon which the electrochemical process, elec troplating, and electrowinning industries are based. 

Figure 16.1 Simple dry cell battery. Electrons are conducted along the external circuit (4), which physically connects the active (2) and noble (1) materials. An equivalent ionic counter-current is conducted through the electrolyte (3), thereby completing the circuit.

As corrosion proceeds, reaction by-products may form on the metal surfaces, creating a resistance to electrical exchanges at these surfaces. Consequently, the reaction rate diminishes correspondingly. If the corrosion reaction is stopped, a time-dependent recovery occurs if the reaction is restarted, the initial corrosion rate is reestablished. This effect is often observed in conventional dry cells and automobile batteries. 

Figure 17 Mechanistic correlation between dry cell and graphitic corrosion.

A number of limitations are imposed by the construction of the instrument and its operating parts, including such factors as fully charged or new dry cell batteries, replacement of drying agents or other chemicals and, of course, how well the moving or consumable parts such as filaments have been maintained. Most instrument failures from these causes can be prevented by routine care and maintenance, and by periodic calibrations. 

Disposable The opposite of a cleanable filter, which after collecting a certain dust burden is thrown away. Dry cell panel A dry filter mounted in a rigid frame. In the past these were manufactured from woven fabrics and felts however, synthetic fibers are replacing these. They have fiber diameters of 20 pm with average spacing of 300 pm and allow air velocity in the 2 m s-1 range. 

Trocken-element, n. dry cell, -entgasung, /. dry distillation, -extrakt, m. dry extract, -farbe,/. dry color, pigment pastel color. 

The resultant fermentation broth was centrifuged to harvest the microbial cells, and they were washed with water and centrifuged a second time, whereupon a living cell paste was obtained. (There was obtained an amount of cells equivalent to 54 parts on a dry basis, which contained 920 /Jg of ubiquinone-10 per gram of dry cells.)... 

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