Silver plating with

Figure 6. Streak-analysis data for Sasanian-style silver plates with a design depicting a king (frequently on horseback) hunting wild game.

Dentistry. Most casting alloys meet the composition and properties criteria of specification no. 5 of the American Dental Association (37) which prescribes four types of alloy systems constituted of gold—silver—copper with addition of platinum, palladium, and 2inc. Composition ranges are specified, as are mechanical properties and minimum fusion temperatures. Wrought alloys for plates also may include the same constituents. Similarly, specification no. 7 prescribes nickel and two types of alloys for dental wires with the same alloy constituents (see Dental materials). 

Potassium cyanide is primarily used for fine silver plating but is also used for dyes and specialty products (see Electroplating). Electrolytic refining of platinum is carried out in fused potassium cyanide baths, in which a separation from silver is effected. Potassium cyanide is also a component of the electrolyte for the analytical separation of gold, silver, and copper from platinum. It is used with sodium cyanide for nitriding steel and also in mixtures for metal coloring by chemical or electrolytic processes. 

Most electroless silver appHcations are for silvering glass or metallizing record masters. Mirror production is the principal usage for electroless silver. The glass support is cleaned, catalyzed using a two-step catalyst, and coated on one side with an opaque silver film (46). Silver-plated nylon cloth is used as a bacteriostatic wound dressing. A tiny current appHed to the cloth causes slow silver dissolution. The silver acts as a bactericide (47). 

Bus conductor with plain connection joints Bus conductor with silver plated or welded contact surfaces... 

Pure uninhibited tetrafluoroethylene can polymerise with violence, even at temperatures initially below that of room temperature. There is little published information concerning details of commercial polymerisation. In one patent example a silver-plated reactor was quarter-filled with a solution consisting of 0.2 parts ammonium persulphate, 1.5 parts borax and 100 parts water, and with a pH of 9.2. The reactor was closed and evacuated, and 30 parts of monomer... 

The first permanent images were obtained by the French landowner . N. Niepce using bitumcn-coated pewter (bitumen hardens when expo.sed to light for several hours and the unexposed portions can then be dissolved away in oil of turpentine). He then helped the portrait painter, L. J. M. Daguerre, to perfect the daguerreotype process which utilized plates of copper coated with silver sensitized with iodine vapour. The announcement of this process in 1839 was greeted with enormous enthusiasm but it. suffered from the critical drawback that each picture was unique and could not be duplicated. 

Silver and gold Silver is nearly always deposited from cyanide baths, though other baths have been described. To limit oxidation and polymerisation in high-speed selective plating with insoluble anodes, low-cyanide baths have been developed containing salts such as phosphate. ... 

Copper and silver tarnish readily in sulphide atmospheres, and copper in contact with sulphur-vulcanised rubber will sometimes react with the sulphur, devulcanising it in the process. The growth of conducting sulphide whiskers on silver is noteworthy as these whiskers may give rise to short circuits across silver-plated contacts. Ammonia has little effect on most metals, but traces will tarnish many copper alloys and cause stress-corrosion cracking of certain stressed brasses. 

A baby s spoon with an area of 6.25 cm2 is plated with silver from AgN03 using a current of 2.00 A for two hours and 25 minutes. 

This electrode is perhaps next in importance to the calomel electrode as a reference electrode. It consists of a silver wire or a silver-plated platinum wire, coated electrolytically with a thin layer of silver chloride, dipping into a potassium chloride solution of known concentration which is saturated with silver chloride this is achieved by the addition of two or three drops of 0.1M silver nitrate solution. Saturated potassium chloride solution is most commonly employed in the electrode, but 1M or 0.1 M solutions can equally well be used as explained in Section 15.1, the potential of the electrode is governed by the activity of the chloride ions in the potassium chloride solution. 

Prepare an approximately 0.1 M silver nitrate solution. Place 0.1169 g of dry sodium chloride in the beaker, add 100 mL of water, and stir until dissolved. Use a silver wire electrode (or a silver-plated platinum wire), and a silver-silver chloride or a saturated calomel reference electrode separated from the solution by a potassium nitrate-agar bridge (see below). Titrate the sodium chloride solution with the silver nitrate solution following the general procedure described in Experiment 1 it is important to have efficient stirring and to wait long enough after each addition of titrant for the e.m.f. to become steady. Continue the titration 5 mL beyond the end point. Determine the end point and thence the molarity of the silver nitrate solution. 

Cathodic protection equipment has been used very successfully in water tanks and HW and steam boilers as anticorrosion devices for 100 years or more. Such equipment comes in many shapes and sizes, and comprises a sacrificial anode of either zinc or magnesium alloy, either bolted directly to a suitable internal water-wetted (cathodic) metal surface, or self-contained by enclosing the anode with a suitable cathode (such as a silver plated base metal). Usually several devices are required for any boiler, more for larger units and less for smaller ones, and these require replacement every one to two years. 

Other metallic elements form ionic compounds with cation charges ranging from -F1 to + 3. Aluminum nitrate nonahydrate, A1 (N03)3 9 H2 O, is composed of cations, NO3 anions, and water molecules. Silver nitrate (AgNO ), which contains Ag cations, is a soluble silver salt that is used in silver plating. 

Silica-gel-precoated preparative TLC plates impregnated with AgNOj are widely applied in this technique [60,90]. To impregnate a silica-precoated plate with silver nitrate, the plate is dipped for 3 min in a 1% AgNOj solution in a methanol-water mixture (4 1, v v). The plate is then dried, first in air with exclusion of light, and next, it is activated at 80°C in a drying oven. If impregnated plates are not used immediately, they should be stored wrapped in black plastic film in a desiccator [90-92]. 

Although not essential, one often uses a previously coated AgCl-Ag electrode or a silver-plated Pt wire coated electrolytically in KC1 solution with a thin deposit of AgCl. Such dry AgCl-Ag electrodes are much in favour as reference electrodes (although in the absence of oxidants), in addition to calomel electrodes (Pt wire in contact with Hg, covered with calomel paste in contact with KC1 solution), which also belong to the second kind, viz.,... 

One must realize that once complete metal deposition has been attained, the emf across the electrodes cannot be switched off before the cathode has been taken out of the solution and rinsed with water, otherwise the metal deposit may start to redissolv e in the solution as a consequence of internal electrolysis by the counter emf. After disconnection the electrode is rinsed with acetone and dried at 100-110° C for 3-4 min. The analytical result is usually obtained from difference in weight of the dry cathode before and after electrolysis. In a few instances a copper- or silver-plated Pt cathode or even an Ag cathode is used, e.g., Zn and Bi are difficult to remove entirely from Pt, as they leave black stains and on heating form an alloy with the noble metal for this and other reasons (see below) the experimenter should consult the prescriptions in handbooks149. 

Zinc electrowinning takes place in an electrolytic cell and involves running an electric current from a lead-silver alloy anode through the aqueous zinc solution. This process charges the suspended zinc and forces it to deposit onto an aluminum cathode (a plate with an opposite charge) that is immersed in the solution. Every 24 to 48 h, each cell is shut down, the zinc-coated cathodes removed and rinsed, and the zinc mechanically stripped from the aluminum plates. The zinc concentrate is then melted and cast into ingots, and is often as high as 99.995% pure. 

Contact of aqueous ethylene glycol solutions with d.c.-energised silvered copper wires causes ignition of the latter. Bare copper or nickel- or tin-plated wires were inert and silver-plated wire can be made so by adding benzotriazole as a metal deactivator to the coolant solution [1], This problem of electrical connector fires in aircraft has been studied in detail to identify the significant factors [2],... 

Indicator Electrodes Silver wire or Platinum wire or gauze plated with silver and sealed into... 

Applying Concepts The tarnish on silver is silver sulfide, which is formed when the silver reacts with sulfide compounds in the environment. In this miniLAB, you will use an oxidation-reduction reaction to remove the tarnish from silver or a silver-plated object. 

In the weeks and months that followed, Jeanne refined and adapted her stories with virtuosic brilliance. From the outset she adopted the dual roles of victimized orphan and imperious princess of the blood. As a Valois, she insisted on a silver plate to eat off and a feather bed to sleep on. She d had the foresight to sneak off a message to Baroness d Oliva, ordering her to flee the country so as not to risk her life. Poor bewildered Nicole set off for Brussels immediately. Nicolas La Motte and Retaux had already left. Now that Jeanne s accomplices were safely out of the way, she concentrated on blaming the Copt and the cardinal. 

In a related study, silver microtubules were produced by chemical deposition [38]. Similar to electrochemical deposition, the surface of the membrane must first be modified, not with a silane but with a catalyst such as Sn ions. Initially, one side of the membrane is protected by tape (Figure 1.12b) and then the surface is activated with SnCh (Figure 1.12c). The activated membrane was then placed into a solution of silver-plating solution (Figure 1.12d). This resulted in the deposition of silver over the activated surface finally the alumina membrane was dissolved away. 

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