Moist paste

Sodium bicarbonate is a gastric antacid that may cause systemic alkalosis on overdose and may contribute to edema owing to sodium retention. It is useful for systemic acidosis because both deficient ions are present in the same molecule, and it can be used topically as a moist paste or in solution as an antipmritic. Sodium bicarbonate also is an ingredient of many effervescent mixtures, alkaline solutions, etc. One gram of NaHCO neutralizes 115 mL 0.1 NHCl. 

FIGURE 12.21 A commercial dry cell. The dry cell is also called the Leclanche cell, for Georges Leclanche, the French engineer who invented it in about 1866. The electrolyte is a moist paste. 

Trinitrophenol can only be stored safely in the form of a paste with water. Lead, mercury, copper, zinc, iron and nickel salts are sensitive to impact, friction and heat. Sodium, ammonium and amine salts give rise to explosions. When it was poured on to a cement floor, trinitrophenol formed a calcium salt that detonated when it came into contact with shoes. Trinitrophenol salts in the form of moist paste are stable. Aluminium salt is not explosive, but combusts spontaneously when in contact with water. 

A dry cell contains a zinc anode and an inert graphite cathode, as shown in Figure 11.7. The electrolyte is a moist paste of manganese(IV) oxide, Mn02, zinc chloride, ZnGh, ammonium chloride, NH4CI, and carbon black, C(s), also known as soot. 

The free base form of 3,3 -dichlorobenzidine is no longer utilized by industry in the United States. It is primarily supplied as the dihydrochloride salt (CPMA 1998). When it was used as the free base, it was handled as a powder or a moist paste (NIOSH 1980). 3,3 -Dichlorobenzidine is not a volatile chemical. 

A slower-burning mixture is preferred over a more rapid one. The slower release of energy allows for better heat transfer to the main composition. Also, most "first fires" are pressed into place or added as moist pastes (that harden on drying), rather than used as faster-burning loose powders. 

The ordinary dry cell (Leclanche cell) is a primary cell that is used in flashlights. In this cell, oxidation occurs at a zinc anode, and reduction at an inert carbon +" cathode (graphite). The space between the cell is filled with a moist paste of Mn02, ZnCl2 and NH CI. The half-reaction at the anode is as follows ... 

The Leclanche cell, the inexpensive disposable flashlight-type cell, has been on the market for over 100 years, yet its chemistry is not completely understood. The cell consists of an outer zinc shell that acts as the anode (seen by the external circuit as the source of electrons and hence the negative terminal) and oxidizes away during operation of the cell, a carbon rod or disk that serves as the cathodic current collector (positive terminal), and a moist paste of manganese dioxide, ammonium chloride, and zinc chloride that fills the cell and acts as both the electrolyte and the source of the cathodic reaction (reduction of MnIV). Usually, graphite in the form of carbon black is added to the paste to increase the electrical conductivity. The basic reactions are... 

A dry cell is the workhorse of primary cells.1 Its familiar cylindrical zinc container serves as the anode and in the center is the cathode, a carbon rod. The interior of the container is lined with paper that serves as the porous barrier. The electrolyte is a moist paste of ammonium chloride, manganese(IV) oxide, finely granulated carbon, and an inert filleq usually... 

Artificial indigo is sold as a deep azure powder with coppery reflection, or more commonly as a moist paste. 

Indigo carmine commonly consists of indigotindisulphonic acid or its sodium salt, which is sold as a moist paste or in blue balls or lozenges with reddish reflection. Indigotinmonosulphonic acid (iindigo purple) is little used. Pure indigo carmine is completely soluble in water, from which it is reprecipitated by addition of sodium chloride. Commercial carmines of low quality leave a more or less abundant greenish residue insoluble in water. 

The design criteria for each electrochemical cell depend on the use that will be made of the cell. For example, for an inexpensive disposable dry-cell flashlight battery, a carbon electrode surrounded by a moist paste of Mn02 and graphite in ZnCl2 -NH4CI is used. The outer electrode is Zn foil. This cell is diagramed as... 

In this cell, a paste containing KOH is the electrolyte. In the older type of dry cell, the electrolyte is a moist paste of NH4Cl/ZnCl2. As has been mentioned in several places in this book, the NH4+ ion is an acid so there is a slow reaction between the metal container and the electrolyte, which causes the battery to deteriorate. 

Dowex 50 (H+ form)—Mix 1 kg of Dowex 50, X-8, 20 to 50 mesh, with 20 liters of dilute HC1 (3 liters of concentrated HC1 +17 liters of distilled water), stir for 5 min, fill with additional H20, and decant. Wash by decantation or suspension and vacuum filtration until the eluate no longer yields any titrat-able acidity (pH 3 to 4). Drain the resin until a moist paste is obtained. Each pair of students will need about 350 ml of moist Dowex 50. The resin should be collected at the end of the experiment (Do not allow accidental mixing with IR-45) and promptly regenerated by the above procedure. Store tightly covered under a water layer. (See note following IR-45 preparation.)... 

Leclanche cell. A electrolydc cell that uses a moist paste rather than a liquid as an electrolyte. Flashlight batteries are dry cells with a zinc cup for an... 

To the moist paste (obtained in step 1), add 5 grams of ammonium picrate (with an average particle size of 4 microns), and 40 grams of water. Then heat the mixture to 90 Celsius with stirring, and continue heating and stirring until most of the water has evaporated (until only a moist paste remains). When most of the water has evaporated, remove the heat source and then place the moist paste into a shallow pan and allow it to stand until dry. 

The calculators, electronic watches, portable radios, and tape players that are so familiar to us are all powered by small, efficient, dry cell batteries. The common dry cell battery was invented more than 100 years ago by George Leclanche (1839-1882), a French chemist. In its acid version the dry cell battery contains a zinc inner case that acts as the anode and a carbon rod in contact with a moist paste of solid Mn02, solid NH4C1, and carbon that acts as the cathode (Fig. 11.14). The half-cell reactions are complex but can be approximated as follows ... 

The so-called dry cell actually contains a moist paste in which the cathode haif-reaction takes piace. Q in the zinc-carbon dry ceii, the zinc case acts as the anode. o The aikaiine battery uses powdered zinc and is contained in a steei case. 

Paper spacer Moist paste of Z11CI2 and NH4CI Layer of Mn02 Graphite cathode Zinc anode... 

Before an electrocardiogram (ECG) is recorded for a cardiac patient, the ECG leads are usually coated with a moist paste containing sodium chloride. What property of an ionic substance such as NaCl is being made use of ... 

A moist paste of NaCl would contain Na" " and Cl ions in solution and would serve as a conductor of electrical impulses. 

Contains a moist paste instead of a liquid electrolyte... 

Zinc-carbon dry cells A dry cell is an electrochemical cell in which the electrolyte is a moist paste. The paste in a zinc-carbon dry cell consists of zinc chloride, manganese(IV) oxide, ammonium chloride, and a small amount of water inside a zinc case. The zinc shell is the cells anode, where the oxidation of zinc metal occurs according to the following equation. 

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