SUBJECTS hydrofluoric acid

Although the total content of carbohydrate fractions of the three components is similar, as reported by Williams et al., 1990, it was found that protein-rich fractions have a significantly lower glucuronic acid content. Circular dichroism studies conducted on different GA fractions showed that only the AGP and GP components have a secondary structure (Renard et al., 2006). The AGP fraction was isolated by gel filtration chromatography and subjected to deglycosylation with hydrofluoric acid (HF) to separate the protein (Qi et al., 1991). About 400 amino acids were contained by the AGP protein fraction ( 33% are... 

It is useful to treat the raffinate to recover the two acids it contains. The raffinate can first be subjected to a thermal treatment which decomposes it into insoluble metallic oxides, hydrofluoric acid and sulfuric acid. In a first scrubbing, sulfuric acid is recovered, whilst in a second stage, hydrofluoric acid is absorbed. When put into operation, this process not only causes a reduction in the amount of sludges but also leads to acid production for return to the process. 

Newer and more complex humus extractions have been developed. These typically involve more steps such as both physical separation on the basis of density and particle size (related to the size of soil inorganic components), and chemical separation based on extractions and washings with hydrofluoric acid (HF), hydrochloric acid (HC1), and sodium hydroxide (NaOH). The products of such separations are then subjected to spectroscopic analysis and interpretation [22,23],... 

Because fluorine is the most reactive of the elements, free fluorine is rarely found in nature. Fluorine reacts with water to produce ozone and hydrofluoric acid. In humans, the inhalation of high concentrations causes laryngeal spasm and bronchospasm, followed by the delayed onset of pulmonary edema. At sub-lethal levels, severe local irritation and laryngeal spasm will preclude voluntary exposure to high concentration unless the individual is trapped or incapacitated. Two human subjects found momentary exposure to 50 ppm intolerable 2 5 ppm was tolerated briefly, but both subjects developed sore throat and chest pain that persisted for 6 hours. Short-term exposures to concentrations up to 10 ppm were tolerated without discomfort. ... 

The hydrofluoric acid, however, attacks glass rapidly when tire action is exerted on a small surface, and much acid is employed. This property has been turned to account to etch glasB the acid is employed in a gaseous or liquid state, according to the occasion and the end proposed. The gaseous acid produces opaque traces the liquid acid transparent ones, Bnt the subject of etching on glass will be alluded to afterwards. 

Many sulfuric and hydrofluoric acid alkylation units have more or less corrosion in some parts of the alkylation unit. Because the types, causes, locations, and remedies for the corrosion are entirely different, it is necessary to have a separate discussion of the two acids on this subject. 

Hydrofluoric acid causes two types of corrosion, direct corrosion, in which iron fluoride is formed, and stress corrosion, in which the metal cracks. Electrolytic corrosion can also take place when the acid becomes diluted with water and two dissimilar metals or carbon are used. Because of the possibility of stress corrosion, all vessels in acid service must be stress-relieved. Monel is also subject to stress corrosion and must be stress-relieved. Care must be taken in stress-relieving Monel that sulfur or sulfur compounds do not come in contact with the Monel either before or during the heat treatment. 

Pyroceramic and ceramic tops are impervious to most chemical spills. The exceptions are typically any of the chemicals that can attack glass, such as hydrofluoric acid, alkali solutions, and hot phosphoric acid. Metal-topped hot plates can take more physical abuse than ceramic or pyroceramic tops. In addition, with metal, there are no concerns about scratches or cracks that, on a pyroceramic top, could lead to further deterioration. Metal-topped hot plates are, however, subject to corrosion from chemical spills. 

The Pharmaceutical Institute of L. W. Gans of Frankfurt3 has made known a process for electrochcrnically preparing fluorine-substitution products of albumens. The latter are suspended, or dissolved in a dilute aqueous solution of hydrofluoric acid or salts of this acid, and subjected at a platinum electrode to the anode current action. The discharged fluorine reacts with the albumen, forming substitution products. 

There are several types of nebulisers, for example the concentric quartz system (Fig. 3.9) or cross-flow system (Fig. 3.10) the tips of which are made from synthetic material or precious stones. The first system can be subject to blockage with solutions containing as little as 0.1% of dissolved salts due to its small capillary inlet. The second system is less fragile and is resistant to corrosion from solutions containing hydrofluoric acid. 

Two additional hydrofluoric acid methods have been reported (1,2), and are similar to that described above. The method of Hughes et al. has also been the subject of two comparative studies relevant to the analysis of ceramics (2,31). Techniques that retain silicon have been discussed (1,2) and involve either fusion with lithium metaborate [or sodium carbonate (2)] or high pressure dissolution in a PTFE bomb. An alternative high pressure method, developed by Price and Whiteside (32), was evaluated in the course of this investigation but was found to be unreliable for stained glass of medieval composition in many experiments dissolution was incomplete. Attempts to modify the procedure by varying the prescribed dissolution parameters produced insufficiently consistent results although superior conditions were established (Table I). 

Within the last few years, there have been several instances in which independent brick liners have experienced problems in resisting the effects of wet flue gases. In certain instances the problems have been due to actual deterioration of mortar and/or brick which were subjected to chemical attack by certain constituents of either the flue gas itself or carry over" reagents from the flue gas desulfurization system. In general, the commonly used silicate mortars for chimneys are quite resistant to a wide range of acids and actually thrive in a wet acid environment. However, certain acids, such as hydrofluoric acid, and most... 

Various other chemical and technical subjects, not directly discussing the products of their publishing company, are reviewed in house organs. Lvbricationy a publication devoted to discussions of the selection and use of lubricants, in the May-June issues of 1950 presented a general review of the concepts and measurements of viscosity. Inco Corrosion Reporter in each issue discusses the chemistry and manufacture of some corrosive material, such as fluorine, chlorine, phosphorus, or hydrofluoric acid. Interchemical Review has published reviews of spot test analysis, the organic chemistry of dyes, and other chemical subjects. 

The geochemical behaviour of Cs and Pu in Solway floodplain cores, collected from Southwick Water, south-west Scotland, has been studied by Allan et al. (1991) by employing a sequential leaching scheme (Cook et al., 1984 Livens Baxter, 1988b McDonald et al., 1990). This scheme incorporates solutions of calcium chloride (readily available sites), acetic acid (specific adsorption sites), tetra-sodium pyrophosphate (organically associated), ammonium oxalate/oxalic acid, (Fe and Mn secondary minerals), dilute nitric acid (dilute acid soluble sites) and nitric acid/ hydrofluoric acid (residual fraction). This technique has been subject to... 

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