Reaction Of Lime Research Articles

Studies on the system sodium oxide‐calcium oxide‐silica‐water

AbstractIn hydrothermal reactions of lime and quartz with water or aqueous NaOH at 150 °C or 180 °C and Ca: Si = 0.83, the rate of reaction of the quartz increases with NaOH concentration. At 180 °C and Ca: Si = 0.83, the conversion into tobermorite of the semi‐crystalline calcium hydrosilicate initially formed occurs more slowly at NaOH concentrations of 0.15–2.00 M (NaOH: SiO2 = 0.05 to 0.63) than in water or 5 M‐NaOH. With long reaction times at 180 °C and Ca: Si = 0.83, increasing NaOH concentration causes pectolite to replace xonotlite as the main product. At very low water contents, NaCaHSiO4 is formed; this compound is conveniently made by grinding together solid NaOH, Ca(OH)2 and quartz in normally humid air and heating the mixture in a closed vessel at 180 °C.

Susceptibility of Citrus spp. and the Other Related Plants to the Satsuma Dwarf Virus (SDV)

Seedlings of 18 Citrus spp., 1 Poncirus sp., 1 Aeglopsis sp., and 7 hybrid varieties were tested for their reaction to the Satsuma dwarf virus (SDV). The tests, conducted under the greenhouse condition (15-30°C), showed that all of the seedlings inoculated were susceptible and induced non-persistent mottling, and less frequently, some lines of the seedlings (Table 3, Fig. 4, F and G) were accompanied by crinkling 1-2 months after bud-inoculation. The viruliferous buds from the respective seedlings whose foliar symptoms had disappeared incited the typical dwarf symptoms upon further transfer to virus-free Satsuma budlings. Mottling, being of either flecking or oak-leaf-like pattern, was noticed shortly after inoculation. But there was consistent delay (3 months or more) in the formation of both leaf-bending and cupping (boat and spoon-shape) symptoms on the leaves of Satsuma seedlings and budlings.A lime-reactive component, or tristeza virus (TV), was present as a consistently recoverable contaminant from the dwarfed trees in the field. The TV component was successfully separated from the SDV component by a prior passage through Poncirus trifoliata seedlings, which, upon further transfer to West Indian lime seedlings, manifested no lime reaction (Table 1 and 2; Fig. 1, B). This finding thus enabled the writer to observe the infectivity of the SDV component by itself to West Indian lime, which, otherwise, was too sensitive to the TV component.The inocula containing either SDV by itself or two components, that is, SDV and TV, caused no difference in the symptomatic expression of Satsuma nucellar seedlings and budlings (Fig. 2). Out of 7 virus isolates used in this test, there were some noticeable differences in their respective virulence to various nucellar seedlings. It is yet to be determined whether these differences are attributable to the presence of SDV strains or not.

Lime reactivity and solution rates

Lime reactivity and solution rates

Reactivity of lime and related oxides. XVII. Sulphating of lime with magnesium and aluminium sulphates

AbstractLime water and solid hydrated lime have been sulphated with magnesium and aluminium sulphate solutions. Changes in phase composition and sulphating rates are followed from pH (glass electrode) and conductivity measurements. The crystallinities of the products have been compared with calcium sulphate dihydrate precipitated directly from solution by double decomposition and subsequently aged.The reactions with the solid hydrated lime are not appreciably impeded by the insoluble products, magnesium and aluminium hydroxides, which are very finely divided. These compounds provide additional surface on which most of the gypsum can form a gel when the gypsum solution saturation ratios have become sufficiently high.The small amounts of gypsum ultimately separating out from the lime water have crystallinity inferior to the larger amounts formed from the solid hydrated lime. Both are still inferior to gypsum from acid‐sulphated lime, and are more comparable with gypsums precipitated from calcium nitrate in acidic media containing concentrations (±0.1 %) of albumen, or from calcium chloride in neutral media. Slower gypsum precipitation from calcium chloride with sulphuric acid (as in the manufacture of ‘Pearl hardening’) gives a more consistent degree of crystallinity.

Reactivity of lime and related oxides. XVIII. Production of plasters

AbstractConditions for production of plasters are surveyed in relation to variations in phase composition, surface area and crystallite size.The commercially known α‐ and β‐hemihydrate plasters prepared by autoclaving and dry calcination are not two distinct phases—they differ in crystal habit, surface area, crystallite size and lattice perfection. The terminal β‐hemihydrate and γ‐CaSO4 produced in vacuo have greater surface areas than samples produced in air.The most active γ‐CaSO4 (Class C plaster) samples are finely porous and rapidly rehydrate in atmospheric water vapour with considerable loss of surface area and porosity. ‘Wet’ rehydration (liquid water) or γ‐CaSO4 causes more rapid development of the 6.01 Å (10.10) spacing, in accord with the c‐direction elongation of the ‘α’‐hemihydrate crystals prepared by autoclaving or precipitation from 50% HNO3.The porosity of the γ‐CaSO4 diminishes considerably between 200° and 300°, but remains to a smaller extent up to 500° when the γ‐CaSO4 has changed to β‐CaSO4, anhydrite (Class D plaster). Anhydrite sintered extensively between 500° and 900° before decomposing to lime at temperatures up to 1400° (Estrich Gips plaster). Removal of the SO2 and O2 is facilitated by streams of nitrogen or carbon dioxide, which increases the decomposition rate. Calcination at temperatures below 1200° gives anhydrite and lime crystals of more comparable sizes, and avoids complete ‘dead‐burning’ of the lime.

Reactivity of lime and related oxides. XVI. Sintering of lime

AbstractCalcium carbonate samples containing known amounts of additives and impurities have been calcined in air at a series of temperatures for different lengths of time. Changes in specific surface and average crystallite size show the effect of the additives and impurities (accessory minerals in limestones and chalks) on the lime sintering.Salt and calcium sulphate each accelerate lime sintering at between 800° and 1100°. The presence of the chloride during the carbonate decomposition affects mainly the subsequent surface activity and sintering behaviour of the lime. Added phosphates have comparatively little influence on lime sintering at 800°, 900° or 1000°. When lime separates from the decomposition of carbonato‐apatites, the phosphate recrystallises to fluor‐apatite and sinters.Ferric oxide progressively increases lime sintering at 800°, 900°, 1000° and 1100°. Like anhydrite, its low Tammann temperature (650°) readily permits ion diffusion into lime cracks and fissures, promoting sintering. Alumina, with a higher Tammann temperature (890°), appreciably enhances lime sintering only above 1100°. The comparatively low Tammann temperature of silica (730°) does not, however, lead to greatly increased lime sintering below 1100°, probably because of formation and separation of calcium silicates with higher Tammann temperatures similar to that of alumina.

Lime Reactivity of Illinois Soils

Laboratory studies have shown that variable strength increases are produced by lime treatment of different fine-grained soils. An extensive study of 38 typical Illinois soils indicated that organic carbon content, soil pH, natural soil drainage, clay mineralogy, horizons, carbonate content, and soil weathering substantially influence soil lime reactivity. Lime reactivity is not significantly correlated with such typical engineering properties as liquid limit, plasticity index, AASHO group index, and percentage < 2 μ clay. Natural soil properties and characteristics can be used to evaluate quantitatively the lime-reactivity potential of a soil.

Reactivity of lime and related oxides. XV. Crystalline forms of sulphated lime

Reactivity of lime and related oxides. XV. Crystalline forms of sulphated lime

Reactivity of lime and related oxides. XV. Crystalline forms of sulphated lime

AbstractChanges in surface area and crystallite size in the interconversions of the forms of sulphated lime have been related to time and temperature conditions.The specific surface increases when hemihydrate, ‘soluble’‐γ‐ and ‘anhydrite’‐β‐calcium sulphate are formed during the thermal decomposition of gypsum. The activation is initially delayed in each dehydration stage, before the products recrystallise to their normal lattice structures. Subsequently, the specific surface decreases (and the average crystallite size increases) as each product sinters.‘Wet’ rehydration of γ‐calcium sulphate rapidly replaces the water in the zeolitic hemihydrate structure, without appreciably ageing it. The less mobile ‘dry’ rehydration in water vapour produces hemihydrate extensively aged. Both ‘wet’ and ‘dry’ conversions of hemihydrate to gypsum are completed with considerable loss of surface. The gypsum crystallinity is more rapidly developed during the ‘wet’ rehydration. Effects of additives on the rehydration and ageing of hemihydrate gypsum plasters have been similarly studied.Anhydrite ‘dry’ rehydrates only very slowly, but ages considerably. ‘Wet’ rehydration slowly produces gypsum of low crystallinity; the surface initially increases, before decreasing greatly as the rehydration accelerates. The rehydration rate finally falls as the material continues to age and improve in gypsum crystallinity.

Reactivity of lime and related oxides. XIV. Sulphating of carbonated lime

Reactivity of lime and related oxides. XIV. Sulphating of carbonated lime

Reactivity of lime and related oxides. XIII. Sulphating of hydrated lime

Reactivity of lime and related oxides. XIII. Sulphating of hydrated lime

Reactivity of lime and related oxides. XIV. Sulphating of carbonated lime

AbstractSamples of carbonated lime (calcitic and vateritic) have been sulphated by N‐H2SO4 and by 0.5M‐Na2SO4 at 22°. Rates of sulphating, changes in surface area and phase composition and crystallite size have been correlated with the surface properties of the initial carbonates. The products have been compared with gypsums obtained by (1) dissolving ground dolomite in N‐H2SO4, and (2) directly precipitating from solution by double decomposition and subsequently ageing.The acid sulphatings are not seriously impeded by the newly formed gypsum; evolution of carbon dioxide evidently prevents the layers becoming impervious. The less active calcium carbonates yield gypsum of surface activity (and average crystallite size) similar to that directly precipitated from 0.5M‐Ca(NO3)2 and N‐H2SO4. The more active calcitic and vateritic samples initially give gelatinous products, before the gypsum crystallises and ages similarly.Sulphating with 0.5M‐Na2SO4 slowly produces increasing alkalinity until about 10% of the calcium carbonate has been converted to gypsum; its crystallinity remains ill‐defined and inferior even to gypsum from hydrated lime.

Reactivity of lime and related oxides. XIII. Sulphating of hydrated lime

AbstractSamples of quicklime and hydrated lime have been sulphated by sulphuric acid and by sodium sulphate solutions at 22°. Rates of sulphating, changes in surface area and phase composition and crystallite size have been correlated with the surface properties of the initial limes. The products have been compared with calcium sulphate dihydrate directly precipitated from solution by double decomposition, and subsequently aged.In acid sulphating, the gypsum from the quicklime has approximately the same specific surface (and average crystallite size) as that directly precipitated from 0.5 M‐calcium nitrate and N‐sulphuric acid. The more active intermediate hydrated lime dissolves more readily and does not impede the sulphating so seriously as the less active initial hydrated lime samples. The latter give products with larger specific surface (smaller average crystallite size) from the more concentrated acid solutions, where the rapid separation of gypsum ultimately impedes the sulphating of the remaining lime.Sulphating with 0.5 M‐soldium sulphate produces increasing alkalinity until about 16% of both the quicklime and the hydrated lime have been converted to gypsum. The sulphate initially separating, probably as a gel, impedes the reaction. The surface decreases until the gypsum begins to crystallise, but its crystallinity remains inferior to that of the acid‐sulphated lime of much lower specific surface.

Some features of tar-bonded dolomite refractories

Bloating and cracking of tar-bonded dolomite refractories during storage, especially in summer, is apparently due mainly to internal hydration of free lime in the body by water formed as a result of the reaction of the lime with organic acids in the pitch-anthracene bond.

Reaction of Sweet Lime to Seedling Yellows, Exocortis, and Xyloporosis Viruses

Reaction of Sweet Lime to Seedling Yellows, Exocortis, and Xyloporosis Viruses

Rapid Reaction of Lime with Hydrous Alumina

CALCIUM aluminate hydrates have recently been reported to form as products of reaction between aluminium-bearing clay minerals and calcium hydroxide at or near room temperatures1,2. The investigation recorded here was initiated to determine whether hydrous alumina would react with calcium hydroxide under similar conditions.

Reactivity of lime and related oxides. XI. Production of dolomitic lime

AbstractThe calcination of dolomite has been studied by determining the changes in specific surface and phase composition and crystallite size during decomposition in vacuo or in air at a series of temperatures up to 900°.The overall surface activities of the dolimes are correspondingly greater than those of the ordinary limes obtained in previous investigations. The calcium oxide crystallites are similar in size to those in ordinary limes, but the magnesium oxide crystallites are much smaller. This is due mainly to the greater volume decrease associated with the magnesium oxide formation. However, this oxide is correspondingly less active than that from magnesite. Hence, some of its sintering is evidently enhanced by the presence of the calcium oxide.At lower temperatures, i.e., below 700° in air, some of the carbon dioxide evolved inhibits the decomposition by recombining with the newly‐formed calcium oxide; this reduces the surface activity of the product. At higher temperatures, the surface activity is also reduced by impurities with lower melting points generally enhancing sintering of the dolime.

Reactivity of lime and related oxides. XII. Hydration of dolomitic lime

AbstractDolomitic lime samples differing widely in surface activity (specific surface, 5–65 m.2g.−1) have been ‘dry’ hydrated by exposure to water vapour at 22° and ‘wet’ hydrated by liquid water at 22° and 95°.In general, the calcium oxide hydrates much more rapidly than the magnesium oxide in the dolimes. During the ‘dry’ hydration of dolime, the calcium hydroxide impedes subsequent hydration of the magnesium oxide. In the ‘wet’ hydrations, changes in surface area and crystal structure resemble those during the separate hydration of lime and magnesia.

Reactivity of lime and related oxides. VIII. Production of activated lime and magnesia

Reactivity of lime and related oxides. VIII. Production of activated lime and magnesia

Reactivity of lime and related oxides. IX. Hydration of magnesium oxide

AbstractMagnesium oxide samples differing widely in surface activity (specific surface 10–180 m.2 g.−1) have been ‘dry’ hydrated by exposure to water vapour at 22° and ‘wet’ hydrated by liquid water at 22° and 95°.The rates of hydration differ considerably, the reaction generally proceeding inwards from the outside of each oxide crystallite by an advancing interface mechanism. Changes in surface area and crystal structure resemble those during the hydration of lime. The more active magnesias age (agglomerate) rapidly in both ‘dry’ and ‘wet’ hydrations, unless the relative water vapour pressures are low; even then, the very slow completion of the hydration ultimately produces considerable ageing.The less active magnesias ‘dry’ hydrate slowly like the less active limes, with splitting of the larger original crystallites increasing the total number present. ‘Wet’ hydration at 22° proceeds with some ageing of the hydroxide, even during the earlier stages and this becomes much greater later. At the higher hydration temperature, 95°, the product ages more rapidly, but the much greater hydration rate produces a time lag in the recrystallisation of the newly‐formed magnesium hydroxide to its normal structure. Later, expansion splits the aged material as the recrystallisation is completed, with the hydration becoming slow and irregular. Magnesias and limes prepared from their respective carbonates at 1000° therefore show similar hydration characteristics.