Ultrapure waters

MV water quality Basic pure water Very pure water Ultrapure water... 

Thate Sven. Specogna Nicola. Eigenberger Gerhart. A Comparison of Different EDI Concepts Used for the Production of High-Purity Water. Ultrapure Water, Tall Oaks Publishing Inc., USA, October 1999. 

The degradation of methyl parathion by hydrolysis and biodegradation was studied in four types of water (ultrapure water, pH 6.1 river water, pH 7.3 filtered river water, pH 7.3 and seawater, pH 8.1) maintained at 6 and 22° C, in the dark. The half-lives of methyl parathion at 6° C in the four water types were determined to be 237, 95, 173, and 233 days, respectively, and the half-lives at 22° C were... 

From Thornton RD and Light TS (1989) A new approach to accurate resistivity measurement of high purity water. Ultrapure Water 6 5). 14-26, with permission. 

The ECD is one of the most easily contaminated detectors and is adversely affected by oxygen and water. Ultrapure, dry gases, freedom from leaks, and clean samples are necessary. Evidence of contamination is usually a noisy baseline or peaks that have small negative dips before and after each peak. Cleaning can sometimes be accomplished by operation with hydrogen carrier gas at a high temperature to bum off impurities, but dismantling is often required. 

Conductivity, water (cleaning) The measurement of the ionic conductivity of water using probes spaced one centimeter part. Expressed in megohms. See also Water, deionized (DI) Water, ultrapure. 

Rinse fluid (cleaning) A fluid used to displace fluids that have potential residue materials. Examples Perfluoro-N-methyl morpholine (3M PF-5052 spot free rinse agent) pure water ultrapure water. 

Water, deionized (DI) (cleaning) Water in which most of the ions, which have a potential for reaction with cleaning materials and/or leaving a residue, have been removed. Often used (erroneously) synonymously with pure water or ultrapure water this is incorrect since DI water can still have organic and particulate contamination. For deionized water the electrical conductivity can be as low as 18.2megohm-cm at room temperature. See also Conductivity Water, ultrapure. 

Water, pure (cleaning) Water purified by reverse osmosis (RO) along with carbon filtration (organics) and mechanical filtration (particulates and living organisms (wee beasties)). Often used as a solvent and as a final rinsing agent when ultrapure water is not required. See also Water, ultrapure. 

Water, semiconductor grade (cleaning) Water that is pure enough to meet the requirements of the semiconductor processing industry. See also Water, ultrapure. 

The most often used subphase is water. Mercury and otlier liquids [12], such as glycerol, have also occasionally been used [13,14]. The water has to be of ultrapure quality. The pH value of tire subphase has to be adjusted and must be controlled, as well as tire ion concentration. Different amphiphiles are differently sensitive to tliese parameters. In general it takes some time until tire whole system is in equilibrium and tire final values of pressure and otlier variables are reached. Organic contaminants cannot always be removed completely. Such contaminants, as well as ions, can have a hannful influence on tire film preparation. In general, all chemicals and materials used in tire film preparation have to be extremely pure and clean. 

Ultraperm Z Ultrapho sphates Ultraphosphoric acid Ultraprene Ultra Pure Ultrapure materials Ultrapure water Ultrason... 

Cmde diketene obtained from the dimeriza tion of ketene is dark brown and contains up to 10% higher ketene oligomers but can be used without further purification. In the cmde form, however, diketene has only limited stabHity. Therefore, especiaHy if it has to be stored for some time, the cmde diketene is distiHed to > 99.5% purity (124). The tarry distiHation residue, containing trike ten e (5) and other oligomers, tends to undergo violent Spontaneous decomposition and is neutralized immediately with water or a low alcohol. Ultrapure diketene (99.99%) can be obtained by crystallization (125,126). Diketene can be stabHized to some extent with agents such as alcohols and even smaH quantities of water [7732-18-5] (127), phenols, boron oxides, sulfur [7704-34-9] (128) and sulfate salts, eg, anhydrous copper sulfate [7758-98-7]. 

Although the principal appHcation of reverse osmosis membranes is still desalination of brackish water or seawater to provide drinking water, a significant market is production of ultrapure water. Such water is used in steam boilers or in the electronics industry, where huge amounts of extremely pure water with a total salt concentration significantly below 1 ppm are required to wash siUcon wafers. 

Some hquid defoamers are preemulsified relatives of paste defoamers. In addition to the fatty components mentioned above, kerosene [8008-20-6] or an organic cosolvent such as 2-propanol have been used to enhance stabiUty of the oil—water emulsion and the solubiUty of the defoamer s active ingredients. These cosolvents are used less frequently as concerns increase about volatile organic emissions (VOCs) from the paper machine. Additionally, the use of ultrapure mineral oil in defoamers has become commonplace. Concern about the creation of 2,3,7,8-tetrachlorodibenzodioxin (TCDD) and 2,3,7,8-tetrachlorodibenzofuran (TCDF) in the pulping process has led to the discovery of unchlorinated precursor molecules, especially in recycled mineral oil and other organic cosolvents used in defoamer formulations (28). In 1995 the mineral oil that is used is essentially free of dibenzodioxin and dibenzofuran. In addition, owing to both the concern about these oils and the fluctuating cost of raw materials, the trend in paper machine defoamers is toward water-based defoamers (29). 

These include wastewater cleanup for electroplating (75—78), radioactive processing (79—82), landfill leachate (76,83), and municipal wastewater (84—87) ultrapure water production for electronics-grade (88,89), laboratory-grade (90), and pharmaceutical-grade (91) materials and food processing (qv) (9). 

RO is also used to produce ultrapure water for many laboratory uses (90) as weU as in the medical and pharmaceutical industries (91). As for the electronics industry, purity is achieved using a combination of processes. A typical hybrid process for the production of ultrapure water is shown in Figure 11. The order in which the various steps take place may vary from case to case. 

Fig. 11. Schematic of membrane-based hybrid process for ultrapure water production.

Boiler feed water pretreatment systems have advanced to such an extent that it is now possible to provide boilers with ultrapure water. However, this degree of purification requires the use of elaborate pretreatment systems. The capital expenditures for such pretreatment equipment trains can be considerable and are often not justified when balanced against the capabiUty of internal treatment. 

Beryllium Oxalate. BeryUium oxalate trihydrate [15771 -43-4], BeC204 -3H20, is obtained by evaporating a solution of beryUium hydroxide or oxide carbonate in a slight excess of oxaHc acid. The compound is very soluble in water. Beryllium oxalate is important for the preparation of ultrapure beryllium hydroxide by thermal decomposition above 320°C. The latter is frequentiy used as a standard for spectrographic analysis of beryUium compounds. 

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