Alloys containing cadmium

Silver-brazed joints are used when temperature or the combination of temperature and pressure is beyond the range of soldered joints. They are also more reliable in the event of plant fires and are more resistant to vibration. If they are used for fluids that are flammable, toxic, or damaging to human tissue, appropriate safeguarding is required by the code. There are OSHA regulations governing the use of silver brazing alloys containing cadmium and other toxic materials. 

It is interesting to note that the behavior of the In atoms depends on whether the cation is Cd or Zn. The In atoms in alloys containing cadmium occupy the octahedral and distorted tetrahedral voids and form, respectively, stable hybrid sp and d sp bonds. 

Care is needed in assessing performance of alloyed zincs because no reliable accelerated tests are available. Many such tests on new electroplating alloys show a much lower corrosion rate relevant to zinc than is eventually found in service. The titanium present in rolled zinc has only a minor influence on corrosion resistance but, after weathering, this alloy develops a dark shade of gray, whereas the previously produced alloy containing cadmium developed a whitish appearance hence it was aesthetically unwise to mix these alloys in the same roof. 

Although the addition of cadmium has particular advantages, fumes given off can have serious health effects. As a result, safer, cadmium-free alloys are available and should be used wherever practicable. Exposure to alloys containing cadmium must be adequately controlled as covered by COSHH Regulations. 

Until recently, many of the gold brazing alloys contained cadmium as an alloying element, which offered the advantages of acting as a melting point depressant and, simultaneously, imparting... 

Solders. Modem dental solders are made from mostly corrosion-resistant, nontoxic metals. Minimal quantities of tin and other elements are often added, some of which could produce toxic effects in the unalloyed state. Each solder is used for specific appHcations (180—188) typical compositions and properties of solders used in dentistry are presented in Table 11. Most of the ingredients of solders are resistant to corrosion, and alloying them with other ingredients renders the alloy safe for use in appHances placed in the oral environment. Silver solders corrode, but are used only for temporary appHances. Available products do not contain cadmium, although cadmium was an ingredient of some silver solders up to ca 1980. 

Cadmium is close to lead and mercury as a metal of current toxicological concern.12346 Extraction of lead and zinc ores, which contain cadmium, pollutes the environment with cadmium. The use of cadmium before 1900 was infrequent however, its valuable metallurgical properties, such as resistance to corrosion, increased its use markedly, for example in the manufacture of alloys and as a coating on steel. It is also now widely used in nickel cadmium ( nicad ) batteries. Coal and other fossil fuels contain cadmium which is released into the environment on combustion. 

Cadmium is used in electroplating, alloys, and batteries, and in some instances as a stabilizer for certain plastics. Zinc minerals contain cadmium, so elevated environmental levels of cadmium can frequently be attributed to the increased dispersal of zinc and zinc compounds [6]. Cadmium has no known function in the human body, and uncomplexed forms of the element are extremely toxic to the kidneys. 

An alloy containing only cadmium and zinc is claimed by the manufacturer to contain 63-percent cadmium by weight. A 356-mg sample of the alloy is dissolved in nitric acid, the solution buffered, and both ZnS and CdS are precipitated by treatment with H2S. The mixed precipitate is dissolved in a solution containing 5 millimoles of ferric sulfate, precipitating sulfur. The filtrate is acidified and the divalent iron is titrated with standard KMn04, 1.60 millimoles of the latter being consumed. How nearly correct is the manufacturer s estimate ... 

Brazing alloys that contain cadmium have been used extensively since mid-19th century. A small amount of cadmium in a gold matrix can lower the melting point below that obtained by adding equivalent concentrations... 

Bismuth alloyed with tin or cadmium is used as a low melting alloy in automatic sprinkler systems for fire prevention. A typical alloy contains 30% Bi. If an 0.80 g sample is dissolved in 50 mL of acid and a chelate formed, how many extractions employing 20.0 mL of benzene will be required to reduce the Bi concentration to... 

Industrial uses of cadmium include electroplating and the manufacture of batteries, metal coatings, and alloys. Cadmium is also used as a pigment in paints and plastics. Some fertilizers also contain cadmium. 

Brass contains about 657o copper and 307o zinc. Would you suggest polarography as a method for determining the main components When and why The alloy contains also 1 % or less of lead and cadmium. Is polarography useful for those metals Explain why or why not. 

Wood s metal A fusible alloy containing 50% bismuth, 25% lead, and 12.5% tin and cadmium. Its low melting point (70°C) leads to its use in fire-protection devices. The alloy is named for the English scientist William Wood (1671-1730). 

Preparations containing cadmium (alloys) and intended to be used for brazing or soldering... 

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