Avoidance calcium

Case Conclusion Diuretics and beta-blockers are first-line agents for treating HTN. Because this patient has asthma, beta-blockers should be avoided. Calcium channel blockers are favorable therapeutic options in patients with both angina and HTN. Because her heart rate is low, diltiazem and verapamil are not optimal choices because they can slow down AV nodal conduction. A long-acting dihydrof ridine, amlodipine, was started. 

Regenerant. Dilute hydrochloric acid (1.4keqm ) or sulfuric acid (0.3-1.0 keqm ), the latter concentration being decided by the calcium content of the raw water thereby avoiding calcium sulfate precipitation. Regeneration levels are typically 1.3-2.0 keq m R injected over a period of about 30 minutes. 

Calcium polycarbophil (FiberCon), methylcellulose (Citrucel), fiber granules (Perdiem), and psyllium hydrophihc mucilloid (Metamucil) are examples of bulk-forming laxatives. Patients with hypercalcemia should avoid calcium polycarbophil because of the calcium in the drug. Metamucil is a nondigestible and nonabsorbent substance that when mixed with water, becomes a viscous solution. There is no protein-binding or half-hfe for the dmg. It is excreted in the feces. There are no systemic effects. Nausea can occur with excessive use. The dry form can cause abdominal cramps. 

Bicarbonate (HC03 ) results from the chemical decomposition of dissolved CO2 with the hydroxide ion in water. A portion of the bicarbonate present in the feed water can be converted to carbonate as a result of pH changes owing to concentration of salts on the concentrate side of the membrane. Such cases require the addition of acid or a crystal growth inhibitor to avoid calcium carbonate scaling. 

It is believed that to avoid any risk of explosion, the electrical conductivity of jet fuel should fall between 50 and 450 pS/m. This level is attained using anti-static additives which are metallic salts (chromium, calcium) added at very low levels on the order of 1 ppm. 

Commercial diethyl carbonate may be purified by the following process. Wash 100 ml. of diethyl carbonate successively with 20 ml. of 10 per cent, sodium carbonate solution, 20 ml. of saturated calcium chloride solution, and 25 ml. of water. Allow to stand for one hour over anhydrous calcium chloride with occasional shaking, filter into a dry fiask containing 5 g. of the same desiccant, and allow to stand for a further hour. Distil and collect the fraction boiling at 125-126°. Diethyl carbonate combines with anhydrous calcium chloride slowly and prolonged contact should therefore be avoided. Anhydrous calcium sulphate may also be used. 

After drying or decomposing a sample, it should be cooled to room temperature in a desiccator to avoid the readsorption of moisture. A desiccator (Figure 2.9) is a closed container that isolates the sample from the atmosphere. A drying agent, called a desiccant, is placed in the bottom of the container. Typical desiccants include calcium chloride and silica gel. A perforated plate sits above the desiccant, providing a shelf for storing samples. Some desiccators are equipped with stopcocks that allow them to be evacuated. 

The most common catalysts are sodium hydroxide and calcium hydroxide, generally used at a modest excess over the nominal stoichiometric amount to avoid formaldehyde-only addition reactions. Calcium hydroxide is cheaper than NaOH, but the latter yields a more facile reaction and separation of the product does not require initial precipitation and filtration of the metal formate (57). 

This carbon dioxide-free solution is usually treated in an external, weU-agitated liming tank called a "prelimer." Then the ammonium chloride reacts with milk of lime and the resultant ammonia gas is vented back to the distiller. Hot calcium chloride solution, containing residual ammonia in the form of ammonium hydroxide, flows back to a lower section of the distiller. Low pressure steam sweeps practically all of the ammonia out of the limed solution. The final solution, known as "distiller waste," contains calcium chloride, unreacted sodium chloride, and excess lime. It is diluted by the condensed steam and the water in which the lime was conveyed to the reaction. Distiller waste also contains inert soHds brought in with the lime. In some plants, calcium chloride [10045-52-4], CaCl, is recovered from part of this solution. Close control of the distillation process is requited in order to thoroughly strip carbon dioxide, avoid waste of lime, and achieve nearly complete ammonia recovery. The hot (56°C) mixture of wet ammonia and carbon dioxide leaving the top of the distiller is cooled to remove water vapor before being sent back to the ammonia absorber. 

Waste treatment of fluoroborate solutions includes a pretreatment with aluminum sulfate to facditate hydrolysis, and final precipitation of fluoride with lime (18). The aluminum sulfate treatment can be avoided by hydrolyzing the fluoroborates at pH 2 in the presence of calcium chloride at this pH, hydrolysis is most rapid at elevated temperature (19). 

Acetylene from calcium carbide can be advantageous in that calcium carbide may be shipped to the point of acetylene usage and acetylene generated on the spot. This avoids the necessity for low pressure, low pressure-drop gaseous acetylene pipelines, or high pressure cylinders for shipping acetylene. 

Maleic Anhydride. The ACGIH threshold limit value in air for maleic anhydride is 0.25 ppm and the OSHA permissible exposure level (PEL) is also 0.25 ppm (181). Maleic anhydride is a corrosive irritant to eyes, skin, and mucous membranes. Pulmonary edema (collection of fluid in the lungs) can result from airborne exposure. Skin contact should be avoided by the use of mbber gloves. Dust respirators should be used when maleic anhydride dust is present. Maleic anhydride is combustible when exposed to heat or flame and can react vigorously on contact with oxidizers. The material reacts exothermically with water or steam. Violent decompositions of maleic anhydride can be catalyzed at high temperature by strong bases (sodium hydroxide, potassium hydroxide, calcium hydroxide, alkaU metals, and amines). Precaution should be taken during the manufacture and use of maleic anhydride to minimize the presence of basic materials. 

Mercury spills should be cleaned up immediately by use of a special vacuum cleaner. The area should then be washed with a dilute calcium sulfide solution. Small quantities of mercury can be picked up by mixing with copper metal granules or powder, or with zinc granules or powder. To avoid or minimize spills, some plants use steel trays as pallets so that a spih, whether of mercury or a mercury compound, is contained on the steel tray. 

A vacuum-retort process (Pidgeon process) was used during World War II for the production of magnesium and calcium. SiHcon, in the form of ferrosihcon, was used as the reducing agent instead of carbon to avoid the problem of cooling magnesium vapor in the presence of carbon dioxide ... 

One method of treatment is to inject calcitonin, which decreases blood Ca " concentration and increases bone calcification (33). Another is to increase the release of calcitonin into the blood by increasing the blood level of Ca " ( 4). This latter treatment is accompHshed by increasing Ca " absorption from the intestine requiring dietary calcium supplements and avoidance of high phosphate diets. The latter decrease Ca " absorption by precipitation of the insoluble calcium phosphate. 

A variety of methods have been devised to stabilize shales. The most successful method uses an oil or synthetic mud that avoids direct contact between the shale and the emulsified water. However, preventing direct contact does not prevent water uptake by the shale, because the organic phase forms a semipermeable membrane on the surface of the wellbore between the emulsified water in the mud and the water in the shale. Depending on the activity of the water, it can be drawn into the shale (activity lower in the shale) or into the mud (activity higher in the shale) (95—97). This osmotic effect is favorable when water is drawn out of the shale thus the aqueous phase of the oil or synthetic mud is maintained at a low water activity by a dding a salt, either sodium chloride or more commonly, calcium chloride. The salt concentration is carried somewhat above the concentration required to balance the water activity in the shale to ensure water movement into the mud. 

Health and Safety Factors. Terephthahc acid has a low order of toxicity. Inhalation by rats for 6 h/d, 5 d/wk for 4 wk produced no fatahties at a dust exposure level of 25 mg/m. The mean acute oral toxicity for rats is over 18 g/kg (86), and for mice over 6 g/kg (87). When terephthahc acid was fed as 3% of the diet to rats, urinary calcuh formed in 90 d, some of which led to cancer. High doses of terephthahc acid lead to formation of calcium terephthalate at levels exceeding its solubihty in urine. This insoluble material leads to the calcuh and provides a threshold below which cancer is not observed (88). Normal precautions used in handling industrial chemicals should be observed with terephthahc acid. If ventilation is inadequate, a toxic-dust respirator should be used to avoid prolonged exposure. 

Zinc oxide is a common activator in mbber formulations. It reacts during vulcanization with most accelerators to form the highly active zinc salt. A preceding reaction with stearic acid forms the hydrocarbon-soluble zinc stearate and Hberates water before the onset of cross-linking (6). In cures at atmospheric pressure, such as continuous extmsions, the prereacted zinc stearate can be used to avoid the evolution of water that would otherwise lead to undesirable porosity. In these appHcations, calcium oxide is also added as a desiccant to remove water from all sources. 

In the second procedure, calcium nitrate was replaced by calcium alkoxide (60). Calcium and sificon alkoxides have very different rates of hydrolysis. To avoid the production of inhomogeneities, a slow and controlled hydrolysis of a mixture of sificon, calcium, and phosphorous alkoxide was performed. The resulting materials were highly homogenous, and monolithic pieces could be produced. The bioactivity of the gel-derived materials is equivalent or greater than melt-derived glasses. 

Caustic soda is removed from the carbonate—bicarbonate solution by treating with a slight excess of hard-burned quicklime (or slaked lime) at 85—90°C in a stirred reactor. The regenerated caustic soda is separated from the calcium carbonate precipitate (lime mud) by centrifuging or rotary vacuum filtration. The lime mud retains 30—35% Hquid and, to avoid loss of caustic soda, must be weU-washed on the filter or centrifuge. Finally, the recovered caustic solution is adjusted to the 10% level for recycle by the addition of 40% makeup caustic soda. 

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