Resistance, acid

The phthaloyl (Phth) derivatives of amines, formed from amines and N-ethoxy-carbonylphthalimide (G.H.L. Nefkens, 1960), are acid-resistant imides, which can be easily deblocked by nucleophilic reagents, most conveniently by hydrazine. 

The only acid-resistant protective group for carbonyl functions is the dicyanomethy-lene group formed by Knoevenagel condensation with malononitrile. Friedel-Crafts acylation conditions, treatment with hot mineral acids, and chlorination with sulfuryl chloride do not affect this group. They have, however, to be cleaved by rather drastic treatment with concentrated alkaline solutions (J.B. Basttis, 1963 H. Fischer, 1932 R.B. Woodward, 1960, 1961). 

The dimensions of concentric-tube nebulizers have been reduced to give microconcentric nebulizers (MCN), which can also be made from acid-resistant material. Sample uptake with these microbore sprayers is only about 50 xl/min, yet they provide such good sample-transfer efficiencies that they have a performance comparable with other pneumatic nebulizers, which consume about 1 ml/min of sample. Careful alignment of the ends of the concentric capillary tubes (the nozzle)... 

Because of the small size of the fluoride ion, F participates in coordination stmctures of high rank. Tantalum and niobium form stable hexafluorotantalate and hexafluoroniobate ions and hydrogen fluoride attacks these usually acid-resistant metals. Hydrogen fluoride in water is a weak acid. Two dissociation constants are... 

The shipment of many commodities may require special barriers on the sacks to impart resistance against hquids or vapors. Other treatments are used to provide grease resistance, acid resistance, and scuff resistance. Special coatings are used in sacks for packing commodities, eg, synthetic mbbers, asphalts, waxes (qv), and resins, to prevent the contents from sticking to the paper. 

The ammonium sulfate and sodium chloride are simultaneously dissolved, preferably ia a heel of ammonium chloride solution. The sodium chloride is typically ia excess of about 5%. The pasty mixture is kept hot and agitated vigorously. When the mixture is separated by vacuum filtration, the filter and all connections are heated to avoid cmst formation. The crystalline sodium sulfate is washed to remove essentially all of the ammonium chloride and the washings recycled to the process. The ammonium chloride filtrate is transferred to acid resistant crystallising pans, concentrated, and cooled to effect crystallisation. The crystalline NH Cl is washed with water to remove sulfate and dried to yield a product of high purity. No attempt is made to recover ammonium chloride remaining ia solution. The mother Hquor remaining after crystallisation is reused as a heel. 

Liquid sulfur dioxide discolors iron, copper, and brass at ca 300 ppm moisture and produces light scale at ca 0.1 wt % moisture and serious corrosion at ca 0.2 wt % or higher moisture content. Copper and brass can be used to handle wet sulfur dioxide where some corrosion can be tolerated, or where the moisture level is low. Wooden tanks are widely used for sulfurous acid preparation, handling, and storage. Sulfite pulp digestors are made of steel lined with acid-resistant brick. 

Wood is widely used as a stmctural material in the chemical industry because it is resistant to a large variety of chemicals. Its resistance to mild acids is far superior to that of steel but not as good as some of the more expensive acid-resistant alloys. Wood tanks used to store cold, dilute acid have a relatively long service life. However, increasing concentration or temperature causes the wood tank to deteriorate rapidly (6). 

Chromium is highly acid-resistant and is only attacked by hydrochloric, hydrofluoric, and sulfuric acids. It is also resistant to other common corroding agents including acetone, alcohols, ammonia, carbon dioxide, carbon disulfide, foodstuffs, petroleum products, phenols, sodium hydroxide, and sulfur dioxide. 

Molecular sieves are also inert to most fluids and are physicaHy stable when wetted with water. Strong inorganic acids or alkaHes and temperatures above 700°C should be avoided. Mildly acidic streams can be dried with a molecular sieve of an acid-resistant type (29). 

The effects of specific fillers in molded goods appHcations are known (52), and are of special importance for water- and acid-resistant compounds. It is good pohcy to contact the suppHers for specific recommendations to meet the balance of properties required. 

Diluent CAS Registry Flexi-bil Effi-cien Solvent Acid resistance Pot-life... 

Cast-iron flanges (ANSI B16.1, 125-lb bolt spacing) are permanently attached to the porcelain with high strength acid-resistant cement. Flanged chemical-porcelain 90° and 45° elbows, tees, crosses, reducers, caps, and globe valves of the Y pattern are available. Armored chemical porcelain is furnished with 1.5- to 2.4-mm- (Mfi- to... 

Generic name and description Breaking tenacity, g/denier Abrasion resistance Resistance to acids Resistance to alkalies Resistance to oxidizing agents Resistance to solvents Specific gravity Maximum operating temperature, "FI... 

Good Good 100 7.3 Special alloy with good resistance to sulfuric, phosphoric, and fatty acids resistant to clilorides in some environments... 

Unplasticized polyvinyl chlorides (type I) have excellent resistance to oxidizing acids other than concentrated and to most nonoxidizing acids. Resistance is good to weak and strong alkahne materials. Resistance to chlorinated hydrocarbons is not good. Polyvinyhdene chloride, known as Saran, has good resistance to chlorinated hydrocarbons. 

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