Calcium hydroxide advantages

Calcium Chelates (Salicylates). Several successhil dental cements which use the formation of a calcium chelate system (96) were developed based on the reaction of calcium hydroxide [1305-62-0] and various phenohc esters of sahcyhc acid [69-72-7]. The calcium sahcylate [824-35-1] system offers certain advantages over the more widely used zinc oxide—eugenol system. These products are completely bland, antibacterial (97), facihtate the formation of reparative dentin, and do not retard the free-radical polymerization reaction of acryhc monomer systems. The principal deficiencies of this type of cement are its relatively high solubihty, relatively low strength, and low modulus. Less soluble and higher strength calcium-based cements based on dimer and trimer acid have been reported (82). 

Hydrolytic decomposition of these cements is clinically advantageous. Free calcium hydroxide is present in excess so that large amounts of calcium are released which, together with high alkalinity, promotes... 

The solution polycondensation usually works at room temperature in approximately 10% solution in toluene, methylene chloride, N-methylpyrrolidone (NMP), or dry tetrahydrofuran (THE). Tertiary amines (triethylamine) or dispersed calcium hydroxide are added as acid acceptor. This procedure has the following advantages The polycondensation is carried out at low temperature (0-40 °C) it is nevertheless very fast, the reaction usually being over in a few min-... 

As described in US patent 6,777,552, an atorvastatin ester derivative is converted to atorvastatin hemicalcium by mixing the ester derivative with more than 70% excess (molar basis) of calcium hydroxide (see Fig. 1.3). Calcium hydroxide functions as a basic catalyst for the hydrolysis of ester and also supplies calcium ion to form the hemi calcium salt. A significant advantage of this method is that the amount of calcium hydroxide does not have to be as carefully controlled in contrast to the amount of sodium hydroxide and calcium acetate generally controlled in other processes. 

Although this method could be used on a small scale, its use in the treatment of municipal water supplies would involve prohibitive costs. Accordingly, advantage is taken of the fact that the objectionable ions may be removed by treatment with a base such as calcium hydroxide (slaked lime) ... 

Thus any advantage of molybdenum disulphide in an oil in reducing friction will be limited to the boundary and mixed lubrication regions, where the reduction in friction may be considerable. One theoretical analysis suggested that the influence of the dispersed powder depends only on particle shape, size and concentration , or in other words that the dispersed powder is simply forming a physical barrier between the interacting surfaces. It would follow that the same effect could be produced by other dispersed solids, and this was confirmed by studies with zinc sulphide, zinc pyrophosphate and calcium hydroxide. 

Advantages to this modified lignin include stable structure re-usable recovery of solvents for re-use high capacity, determined by the amount of calcium hydroxide used rapid effective in batch or column operations. 

Blast-furnace slag cements with high slag contents have lower heats of hydration than pure Portland cement, which is advantageous for large scale concrete structures (e.g. dams). The lower calcium hydroxide content results in their being somewhat more chemically stable than Portland cement. Blast-furnace slag cements are used in similar applications to Portland cement. 

Hydrolysis by alkali The usual reagent is a solution of sodium hydroxide or potassium hydroxide in water or an alcohol (methanol, ethanol, or diethyleneglycol). Milder reagents are solutions of barium or calcium hydroxide. If fission of an ester gives products that are sensitive to strong alkali, it can often be effected with advantage by a solution of sodium carbonate, sodium hydrogen carbonate, or sodium methoxide.52 For hydrolysis of particularly stable esters, such as n,n -disubstituted aromatic carboxylic esters, it is sometimes necessary to use an alkali melt. 

Pfeil and coworkers presented a model for the synthetic pathway of formose, shown in Scheme 5. A similar, but more detailed, model was given by Mizuno and coworkers, who investigated the intermediates in the reaction by chromatographic fractionation of alditol acetate derivatives by g.l.c. (see Table IV). Weiss and coworkers conceptualized the formose reaction as a consecutive-parallel scheme (see Scheme 6) proceeding to the C level, and reported a series of experiments in the continuously stirred tank-reactor previously mentioned to determine the effect of various concentrations of formaldehyde and calcium hydroxide on the reaction rate. The advantage of the tank reactor is that conversions in the autocatalytic system can be controlled, and reaction rates can be measured directly. When the formaldehyde feed-rate was kept constant, and the feed rate for calcium hydroxide varied, products were obtained... 

In clinical use, setting chelate-type calcium hydroxide materials are considered to have the following advantages ... 

A particular advantage of calcium hydroxide sealers is their anti-bacterial nature, a feature which is related to their high pH. Several in vitro studies have demonstrated that these show considerable anti-bacterial activity [42-44]. Despite their biocidal character, these materials are less toxic than zinc oxide-eugenol sealers towards human periodontal ligament cells [40,41]. 

As aforementioned efflorescence formation is promoted by a high content of sodium and potassium hydroxides. A coefficient K is applied, being the total of calcium, sodium and potassium present in the liquid phase. Though the influence of lime content seems to be obvious, the effect of sodium and potassium is not. As it is known, these components minimalize the solubility of calcium hydroxide and there must be other reasons causing their advantageous effect of efflorescence formation. 

In some cases the hardener is not used and it is taken advantage of calcium hydroxide the catalytic effect, evolved as a product of calcium silicates hydrolysis, at the initial period of alite [61]. At resin content not exceeding 20% by mass of cement the properties of polymer-cement concrete do not differ significantly from those of polymer hardened by traditional method. 

Liquid chromatography Normal-phase systems have the advantage of being directly compatible with extracts in hexane. Silica, alumina, and lime (calcium hydroxide) are all particularly suited to the resolution of carotenoid geometrical isomers cis-trans) and diastereoisomers, but not positional isomers oc/fi-carotene). However, silica may cause on-column artifacts, reproducible retention on alumina is strongly dependent on a rigorous control of the water content of the eluent, and lime columns are not commercially available. 

---