Ultra high purity

Germanium is very similar to Si, but its band gap is too small for many practical applications. Large crystals of ultra-high-purity Ge have been grown for use as gamma-ray detectors. In such crystals, the net concentration of... 

Germanium can be separated from other metals by fractional distillation of its volatile tetrachloride. The techniques permit the production of germanium of ultra-high purity. 

W. H. Whidock, "The Ultra-High Purity Chahenge", in Separation of Gases, Proceeding of the Fifth BOC Priestley Conference, Birmingham, U.K., Sept. 19—21,1989, Royal Society of Chemistry, 1990. 

Boron tribromide [10294-33A], BBr, is used in the manufacture of diborane and in the production of ultra high purity boron (see Boron, ELEMENTAL BoRON COMPOUNDS). Anhydrous aluminum bromide [7727-15-3], AIBr., is used as an acid catalyst in organic syntheses where it is more reactive and more soluble in organic solvents than AlCl. Tballium bromide [7789AOA], TlBr, is claimed as a component in radiographic image conversion panels (39). 

A more recent development in ethylene polymerization is the simplified low pressure LDPE process. The pressure range is 0.7—2.1 MPa with temperatures less than 100°C. The reaction takes place in the gas phase instead of Hquid phase as in the conventional LDPE technology. These new technologies demand ultra high purity ethylene. 

Abiko, K. (1994) in Ultra High Purity Base Metals (UHPM-94), ed. Abiko, K. et al. (Japan Institute of Metals, Sendai) p. 1. 

Smith, R.L. (ed.) (1962) Ultra-high-purity Metals (American Society for Metals, Metals Park, Ohio). 

Semi-conductors Ultra-high purity water Total organic carbon (TOC) reduction... 

Ultra-high-purity Mg has been prepared by either zone refining or vacuum distillation. Zone refining " is a difficult process because of the high volatility and reactivity of the metal. Nevertheless, the process can be carried out in SOj atmospheres where protective films of MgS04 and MgO are formed " ", or in ultra-pure Ar atmospheres "". Zone refining removes a number of major impurities, includ-... 

The iron powder was prepared by reducing ultra-high purity... 

Czochralski seeded single-crystal growth from semiconductors stable as melts, which yields the meters-large single crystals of ultra-high purity silicon used in nearly all technological applications. 

Used industrially in the manufacture of diborane, ultra high purity boron, and semiconductors used as a catalyst in polymerizations, alkylations, and acylations. 

Usually, samples are presented for analysis as liquids. Thus, solid samples must be dissolved. Analytical or ultra-high-purity grade reagents must be used for dissolution to prevent contamination at trace levels. Certain volatile metals (e.g. cadmium, lead and zinc) may be lost when dry ashing, and volatile chlorides (e.g. arsenic and chromium) lost upon wet digestion. It is particularly easy to lose mercury during sample preparation. Appropriate steps must be taken in the choice of method of dissolution, acids and conditions (e.g. whether to use reflux conditions) to prevent such losses. 

Dynamic headspace GC utilizes a constant purge of the sample with an ultra-high purity gas (i.e., helium). The purged volatiles are then adsorbed onto a trap, followed by heat desorption onto the GC for analysis. Either a flame ionization detector or mass selective detector can be used. The protocol presented here is designed to analyze a meat sample. 

More recently, ozone has been found to be particularly suitable as a sterilant in bottled water and ultra-high purity water production. 

The constricted part of the tube (Fig. la) was then sealed off, sample transferred in vacua into the Infrasil cell and reduced by hydrogen (Ultra-high purity, Air Products) at 1 atm and 200°C for 14 h in an apparatus (Fig. lb). The temperature of 200°C gives rise to almost complete reduction of the Cu Y to Cu Y without reducing further to Cu° (4). ... 

Traditionally PSA processes have found particularly widespread application in hydrogen production systems wherein the PSA unit is used to produce ultra-high purity hydrogen (99.999%+) from steam-reformed hydrocarbons and other hydrogen sources. However, several limitations have existed with these processes. 

---