Reaction alkali carbonates

The different types of admixtures, known to reduce alkali-aggregate reactions, can be divided into two groups those that are effective in reducing the expansion due to the alkali-silica reaction, and those that lower expansions resulting from the alkali-carbonate reaction. For the alkali-silica reaction, reductions in the expansion of mortar specimens have been obtained with soluble salts of lithium, barium and sodium, proteinaceous air-entraining agents, aluminum powder, CUSO4, sodium silicofluoride, alkyl alkoxy silane,... 

Limestones generally do not contain sufficient reactive silica or silicates to cause expansion, and damaging alkali-carbonate reaction has rarely been reported. The reactions involving carbonate rocks can be either expansive or non-expansive and are more likely to occur when the limestone contains appreciable quantities of dolomite and clay minerals [8.1]. ASTM C586 [8.8] gives a test method for determining the potential alkali reactivity of carbonate rock aggregates. 

Alkali-carbonate reaction is a reaction which can occur under certain conditions between sodium and potassium hydroxides in cement and carbonate rocks (see section 8.3.6). 

Some types of aggregate can react with Na, K and OH ions in the pore solution, giving rise to detrimental expansion. The principal reactions can take place with aggregate containing certain forms of amorphous or poorly crystalline sihca (alkah sihca reaction, ASR) and with dolomitic hmestone aggregate (alkali carbonate reaction). 

Certain carbonated rocks participate in reactions with alkalis that, in some instances, produce detrimental expansion and cracking. These detrimental alkali-carbonate reactions are usually associated with argillaceous dolomitic limestones that have a very fine-grained structure (ACI 2007). 

Gifford, P.M., and Gillot, J. (1996) Alkali-silicate reaction (ASR) and alkali-carbonate reaction (ACR) in activated blast fiunace cement (ABFSC). Cement and Concrete Research 26,21-26. 

An alkali-carbonate reaction may takes place if an argillaceous (illitic) dolomitic hmestone is used as concrete aggregate. Here expansion takes place as the consequence of swelling of the illite eonstituent, following a de-dolomitization of the dolomitic... 

Tang, M. et al. (1994) Studies on alkali-carbonate reaction. ACIMaterials Journal 91,... 

Gillott, J.E. and Swenson. E.G. 1969. Mechanism of alkali carbonate reaction. Quarteriy Journal of Engineering Geology, 2. 7-24. 

Beside the alkali-silica reaction described above, similar phenomena may occur in the case of reactive dolomites and limestones. The so-called alkali-carbonate reaction (ACR) is less frequent and not completely understood. When the effects of ACR are observed, two similar remedies are also necessary either to keep the content of alkalis in concrete as low as possible, or to decrease the percentage of deleterious aggregate in the concrete mix. 

Alkali-carbonate reaction. The alkali-carbonate reaction is different from the alkali-silica reaction in forming different products. Expansive dolomite contains more calcium carbonate than the ideal 50 % (mol) proportion and frequently also contains illite and chlorite clay minerals. 

A halogen atom directly attached to a benzene ring is usually unreactive, unless it is activated by the nature and position of certain other substituent groups. It has been show n by Ullmann, however, that halogen atoms normally of low reactivity will condense with aromatic amines in the presence of an alkali carbonate (to absorb the hydrogen halide formed) and a trace of copper powder or oxide to act as a catalyst. This reaction, known as the Ullmant Condensation, is frequently used to prepare substituted diphenylamines it is exemplified... 

GirhotolAmine Process. This process developed by the Girdler Corporation is similar in operation to the alkali carbonate processes. However, it uses aqueous solutions of an ethanolamine, ie, either mono-, di-, or triethanolamine. The operation of the Girbotol process depends on the reversible nature of the reaction of CO2 with monoetbanolamine [141-43-5] to form monoethanolamine carbonate [21829-52-7]. 

Seven chemical reactions were identified from the chemistry syllabus. These chemical reactions were selected because they were frequently encountered during the 2-year chemistiy course and based on their importance in understanding concepts associated with three topics, namely, acids, bases and salts, metal reactivity series and inorganic chemistry qualitative analysis. The seven types of chemical reactions were combustion of reactive metals in air, chemical reactions between dilute acids and reactive metals, neutralisation reactions between strong acids and strong alkalis, neutralisation reactions between dilute acids and metal oxides, chemical reactions between dilute acids and metal carbonates, ionic precipitation reactions and metal ion displacement reactions. Although two of the chemical reactions involved oxidation and reduction, it was decided not to include the concept of redox in this study as students had only recently been introduced to ion-electron... 

Length change of concrete due to alkali-carbonate rock reaction ASTM C1105... 

Acid chlorides are also used in order to determine whether or no an unidentified substance contains alcoholic or phenolic hydroxyl groups. If a substance reacts with an acid chloride, such a hydroxyl group is present, since all groups in which oxygen is combined in other ways, e.g. in ether linkage, are indifferent to this treatment. The reaction can be considerably facilitated by the addition of alkali or of alkali carbonate. 

Molten Carbonate Fuel Cell (MCFC) The electrolyte in this fuel cell is usually a combination of alkali carbonates, which is retained in a ceramic matrix of LiA102. The fuel cell operates at 600 to 700°C where the alkali carbonates form a highly conductive molten salt, with carbonate ions providing ionic conduction. At the high operating temperatures in MCFCs, Ni (anode) and nickel oxide (cathode) are adequate to promote reaction. Noble metals are not required. 

Colorless, mobde hquid turns yellow on standing very pungent odor refractive index 1.4437 at 20°C density 1.667 g/mL at 20°C vapors heavier than air, vapor density 4.7 (air=l) melts at -51°C bods at 69.4°C sparingly soluble in water, decomposing slowly to sulfuric and hydrochloric acids forms a hydrate S02C12 I5H2O with ice-cold water miscible with benzene, toluene, chloroform, carbon tetrachloride, and glacial acetic acid decomposed by alkalies (violent reaction occurs)... 

Pure decarbonylation typically employs noble metal catalysts. Carbon supported palladium, in particular, is highly elfective for furan and CO formation.Typically, alkali carbonates are added as promoters for the palladium catalyst.The decarbonylation reaction can be carried out at reflux conditions in pure furfural (165 °C), which achieves continuous removal of CO and furan from the reactor. However, a continuous flow system at 159-162 °C gave the highest activity of 36 kg furan per gram of palladium with potassium carbonate added as promoter. In oxidative decarbonylation, gaseous furfural and steam is passed over a catalyst at high temperatures (300 00 °C). Typical catalysts are zinc-iron chromite or zinc-manganese chromite catalyst and furfural can be obtained in yields of... 

Other reported syntheses include the Reimer-Tiemann reaction, in which carbon tetrachloride is condensed with phenol in the presence of potassium hydroxide. A mixture of the ortho- and para-isomers is obtained the para-isomer predominates. -Hydroxybenzoic acid can be synthesized from phenol, carbon monoxide, and an alkali carbonate (52). It can also be obtained by heating alkali salts of -cresol at high temperatures (260—270°C) over metallic oxides, eg, lead dioxide, manganese dioxide, iron oxide, or copper oxide, or with mixed alkali and a copper catalyst (53). Heating potassium salicylate at 240°C for 1—1.5 h results in a 70—80% yield of -hydroxybenzoic acid (54). When the dipotassium salt of salicylic acid is heated in an atmosphere of carbon dioxide, an almost complete conversion to -hydroxybenzoic acid results. They>-aminobenzoic acid can be converted to the diazo acid with nitrous acid followed by hydrolysis. Finally, the sulfo- and halogenobenzoic acids can be fused with alkali. 

Sulfur combines direcdy with hydrogen at 150—200°C to form hydrogen sulfide. Molten sulfur reacts with hydrogen to form hydrogen polysulfides. At red heat, sulfur and carbon unite to form carbon disulfide. This is a commercially important reaction in Europe, although natural gas is used to produce carbon disulfide in the United States. In aqueous solutions of alkali carbonates and alkali and alkaline-earth hydroxides, sulfur reacts to form sulfides, polysulfides, thiosulfates, and sulfites. 

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