Calcium analogs

In analcime-wairakite series (an interesting exeimple of order/disorder in zeolites), wairakite, the calcium analogous to the sodic analcime has a remarkable order. 

One can stop at this point (selective calcium softening) or add enough further lime to precipitate the Mg2+ as Mg(OH)2. In contrast to the calcium analogs, MgC03 is fairly soluble but Mg(OH)2 is not (see Exercises 14.1 to 14.3) ... 

Tabie 14 Interatomic distances (A) in Sr8Rli5D23 and calcium analog... 

The principles at play in water softeners are the same as those in precipitation reactions. Water is run over a dense material saturated with sodium ions like a gigantic network of salts. The sodium salts are soluble, whereas the calcium analogs of the same salts are not. So the calcium replaces the sodium and becomes trapped on or in the solid. The water, now enriched in sodium instead of calcium, can be used without worry that it will precipitate soap or form the crusty deposits of scale. In the regeneration cycle of the water softener, the solid support is backwashed with water saturated with so much sodium salt that the sodium eventually replaces the calcium on the solid, and the water softener is ready to start softening again. 

Strontium-89, a radioisotope, is used in the relief of metastatic bone pain. Strontium-89 chloride is a radiopharmaceutical. Following IV injection, soluble strontium compounds behave like their calcium analogs, clearing rapidly from blood and selectively locahzing in bone mineral. Uptake of strontium by bone occurs preferentially in sites of active osteogenesis. It selectively irradiates sites of primary metastatic bone involvement with minimal effect on soft tissues distant from bone lesions. It is indicated for painful skeletal metastases. 

Six tissues and blood represent the most important sites for intake, metabolism, and deposition in humans. They are important because (1) some inhaled uranium deposits in the lung and is transferred to blood, (2) uranium in blood is transferred via bile to the liver, (3) uranium is excreted through the kidney, a target organ for heavy metal deposition, (4) muscle and (5) fat represent 60% of the total reference body weight, (6) skeleton or bone accumulates calcium analogs and is... 

At room temperature, the bisulfite pH inflection poiat occurs at pH 4.5 and the monosulfite at pH 9. Analogous equations can be written for magnesium, calcium, and ammonia. The starting raw materials, ia addition to sulfur, are sodium hydroxide, magnesium oxide, calcium carbonate, or ammonia, depending on the base used. The four commercial bases used ia the sulfite process are compared ia Table 4. 

Because of its high reactivity, production of barium by such processes as electrolysis of barium compound solution or high temperature carbon reduction is impossible. Electrolysis of an aqueous barium solution yields Ba(OH)2, whereas carbon reduction of an ore such as BaO produces barium carbide [50813-65-5] BaC2, which is analogous to calcium carbide (see Carbides). Attempts to produce barium by electrolysis of molten barium salts, usually BaCl25 met with only limited success (14), perhaps because of the solubiUty of Ba in BaCl2 (1 )-... 

These reactions are thermodynamically unfavorable at temperatures below ca 1500°C. However, at temperatures in the range from 1000 to 1200°C a small but finite equiUbrium pressure of barium vapor is formed at the reaction site. By means of a vacuum pump, the barium vapor can be transported to a cooled region of the reactor where condensation takes place. This destroys the equiUbrium at the reaction site and allows more barium vapor to be formed. The process is completely analogous to that used in the thermal reduction of CaO with aluminum to produce metallic calcium (see Calcium AND CALCIUM alloys). 

A base is any material that produces hydroxide ions when it is dissolved in water. The words alkaline, basic, and caustic are often used synonymously. Common bases include sodium hydroxide (lye), potassium hydroxide (potash lye), and calcium hydroxide (slaked lime). The concepts of strong versus weak bases, and concentrated versus dilute bases are exactly analogous to those for acids. Strong bases such as sodium hydroxide dissociate completely while weak bases such as the amines dissociate only partially. As with acids, bases can be either inorganic or organic. Typical reactions of bases include neutralization of acids, reaction with metals, and reaction with salts ... 

The choice of metal for a reduction depends upon the structure of the compound being reduced. For practical purposes the choice is between lithium and sodium since neither potassium nor calcium offer any advantages. Reductions with sodium require the use of iron-free reagents, but the author prefers to use iron-free reagents with lithium also, in order to ensure that reductions are reproducible. Lithium is required for the reduction of 5-methoxytetralin analogs and for the reduction of heavily alkylated rings such... 

A simple and direct approach to 10(5 4j H)<2Z)eo-5-lceto derivatives lacking functionality in ring A is the controlled pinacol rearrangement of vicinal cw-diols analogous to the process described in the previous section. An example is the reaction of cholestane-4a,5a-diol 4-tosylate (136) with 1 mole-equivalent of potassium t-butoxide or with dimethylforraamide-calcium carbonate at reflux which gives a quantitative yield of Q(5ApH)abeo-cholestan-5-one (137). ... 

Assuming calcium metal reacts in a similar way, write the equation for the analogous reaction between calcium and water. Remember that calcium is in the second column of the periodic table and sodium is in the first. 

AOS 2024 adsorption increases continuously on going from fresh water to 1% NaCl to 4% NaCl. Aqueous 1% NaCl was studied as an analog to aqueous 1% sodium sulfate. The last two entries of Table 19 show that increased AOS 2024 adsorption in the presence of sodium sulfate could mitigate any reduction in calcium ion-promoted surfactant precipitation. However, the larger than usual experimental uncertainty in the sodium sulfate results means that the... 

If one-fourth of the fluorine ions are removed and the others are replaced by oxygen ions, calcium being replaced by (Mn, Fe), a structure is obtained which approximates that of bixbyite, which differs from it only in small displacements of the ions. This similarity is shown by the fact that the highly distorted octahedra have corners which are nearly at six of the eight corners of a cube, the six being chosen differently for the 8e and the 24 e octahedra, as is seen from Fig. 4 and 5. This analogy was, indeed, pointed out by Zachariasen for his incorrect structure. As a matter of fact the "ideal structure, with u = 0 and... 

In the sarcoplasm of smooth muscle cells there is a membrane bound compartment usually referred to as the SR by analogy with skeletal muscle. However, it is not at all clear that the interior of these membrane-bound regions are continuous as they are in skeletal muscle. The primary properties of this system seem to be quite similar to those of the endoplasmic reticulum of many other cell types. In general, calcium is concentrated into the membrane-bound reticulum and then released to initiate the characteristic action of the cell. 

Aziridines can be prepared directly from double-bond compounds by photolysis or thermolysis of a mixture of the substrate and an azide. The reaction has been carried out with R = aryl, cyano, EtOOC, and RSO2, as well as other groups. The reaction can take place by at least two pathways. In one, the azide is converted to a nitrene, which adds to the double bond in a manner analogous to that of carbene addition (15-62). Reaction of NsONHC02Et/ CuO [Ns = A(/7-toluenesulfonyl-inimo)] and a conjugated ketone, for example, leads to the A-carboethoxy aziridine derivative.Calcium oxide has also been used to generate the nitrene.Other specialized reagents have also been used." ... 

Urotensin II Receptor (GPR14). The vasoactive cyclic peptide urotensin II (U-II) is the endogenous ligand of the G protein-coupled orphan receptor GPR14. Structure-activity relationships from 25 peptide analogs, which mobilize intracellular calcium in GPR14-transfected CHO cells, and the... 

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