Calcium contents

Some commonly used primary nutrient fertilizers are incidentally also rich sources of calcium. Ordinary superphosphate contains monocalcium phosphate and gypsum in amounts equivalent to all of the calcium originally present in the phosphate rock. Triple superphosphate contains soluble monocalcium phosphate equivalent to essentially all the P2 5 product. Other fertilizers rich in calcium are calcium nitrate [10124-37-5] calcium ammonium nitrate [39368-85-9] and calcium cyanamide [156-62-7]. The popular ammonium phosphate-based fertilizers are essentially devoid of calcium, but, in view of the natural calcium content of soils, this does not appear to be a problem. 

Commercially available algiaates dissolve ia hot or cold water to produce solutioas with viscosities ranging from a few to several huadred mPa-s(= cP). The actual viscosity depeads oa the molecular weight and calcium content of the algiaate. 

Rea.ctivity ofLea.d—Ca.lcium Alloys. Precise control of the calcium content is required to control the grain stmcture, corrosion resistance, and mechanical properties of lead—calcium alloys. Calcium reacts readily with air and other elements such as antimony, arsenic, and sulfur to produce oxides or intermetaUic compounds (see Calciumand calciumalloys). In these reactions, calcium is lost and suspended soHds reduce fluidity and castibiUty. The very thin grids that are required for automotive batteries are difficult to cast from lead—calcium alloys. 

A rapid method to determine the calcium content of lead alloys is a Hquid-metal titration using lead—antimony (1%) (9). The end point is indicated by a gray oxide film pattern on the surface of a sohdifted sample of the metal when observed at a 45° angle to a light source. The basis for the titration is the reaction between calcium and antimony. The percentage of calcium in the sample can be calculated from the amount of antimony used. If additional calcium is needed in the alloy, the melt is sweetened with a lead—calcium (1 wt %) master alloy. 

Lead—Calcium—Aluminum Alloys. Lead—calcium alloys can be protected against loss of calcium by addition of aluminum. Aluminum provides a protective oxide skin on molten lead—calcium alloys. Even when scrap is remelted, calcium content is maintained by the presence of 0.02 wt % aluminum. Alloys without aluminum rapidly lose calcium, whereas those that contain 0.03 wt % aluminum exhibit negligible calcium losses, as shown in Figure 8 (10). Even with less than optimum aluminum levels, the rate of oxidation is lower than that of aluminum-free alloys. 

Also calcium content must be so as to pass the test. 

A uniform coating of calcium carbonate deposited on the metal surfaces physically segregates the metal from the corrosive environment. To develop the positive LSI required to deposit calcium carbonate, it is usually necessary to adjust the pH or calcium content of the water. Soda ash, caustic soda, or lime (calcium hydroxide) may be used for this adjustment. Lime is usually the most economical alkaH because it raises the calcium content as weU as the alkalinity. 

The maintenance of lime-treated muds consists of monitoring the calcium content, i.e., the proper lime solubility. Since the lime solubility is controlled by the amount of caustic soda present in the mud, the proper alkalinity determination is of great importance. The recommended value of is 5 to 8, and it is maintained with caustic soda the recommended value of P is 25 to 40, and it is maintained with excess lime. The amount of excess lime should be from 5 to 8 Ib/bbl. 

The titration with EDTA, using solochrome black as indicator, will yield the calcium content of the sample (if no magnesium is present) or the total calcium and magnesium content if both metals are present. To determine the individual elements, calcium may be evaluated by titration using a suitable indicator, e.g., Patton and Reeder s indicator or calcon — see Sections 10.48 and 10.60, or by titration with EGTA using zincon as indicator — see Section 10.61. The difference between the two titrations is a measure of the magnesium content. 

The calcium content may then be determined by titration wth EDTA using either Patton and Reeder s indicator or calcon (Section 10.60), or alternatively by titration with EGTA (see Section 10.61). 

Calcium in calcium carbonate. Determine the calcium in an analysed sample of dolomite. Dissolve about 0.38 g, accurately weighed in 1 1 hydrochloric acid, warm gently, filter through a quantitative filter paper, wash, dilute the combined filtrate and washings to 1 L. Measure the calcium content of the resulting solution use a calcium filter. Compare the value for Ca thus obtained with the known Ca content. 

Figure 8.2. Dietary Sr/Ca as a function of the calcium content of plants.

Menzel, R.G. and Heald, W.R. 1959 Strontium and calcium contents of crop plants in relation to exchangeable strontium and calcium in the soil. Proceedings of the Soil Science Society of America 23 110-112. 

Fig. 11. Capillary data showing an increase in the release of intracellular calcium content (340/380 ratio) as s increases. Data refer to experiments in which the cell suspension was circulated through a fine bore capillary for 15 min. Error bars represent the 8.0% standard deviation [87]...

Harrison et al., 1998 10 week old OVX rats low calcium diet treatment starts 2 weeks after OVX Soy protein with isoflavones (6 mg/d) for 4 weeks Reduced bone loss (higher bone weight, higher calcium content) but no decrease of markers of bone turnover for the soy group... 

Yamaguchi and Gao, 1998 Rat femoral-metaphyseal tissues cultured for 48 h with bone resorbing factors PTH, PGE2 or EPS) +/- genistein measured bone calcium content, acid and alkaline phosphatases Genistein (10 Yi O M) inhibited bone resorption. Effect reversed by anti-estrogen, tamoxifen. 

Gao and Yamaguchi, 1999a Yamaguchi and Ma, 2001 Femoral-diaphyseal tissues from elderly female rats cultured for 24 h Daidzein or genistein (lO M, lO M) induced calcium content and alkaline phosphatase (ALP) activity indicating stimulation of bone formation. 

YAMAGUCHI M and MA z J (2001) Effect of polyphenols on calcium content and alkaline phosphatase activity in rat femoral tissues in vitro. Biol Pharm Bull 24, 1437-9. 

Calcium supplements are available in a variety of calcium salts and dosage forms. Calcium requirements are listed in terms of elemental calcium. However, many product labels list calcium content in the salt form, so the percent of elemental calcium must be known to calculate the elemental calcium content per tablet. 

In an attempt to find out how fast the waste was reacting with limestone, a 3-h backflushing experiment, in which waste was allowed to flow back out of the injection well, yielded some unexpected results. The increase in pH of the neutralized waste could not be fully accounted for by the solution of limestone as determined from the calcium content of the backflushed liquid the additional neutralization apparently resulted from reactions between nitric acid and alcohols and ketones in the original waste induced by increased pressure in the injection zone compared to surface conditions.41... 

Herbicide use in forestry causes mineralization, thus decreasing the amount of organic compounds in the soil, as well as the overall nitrogen and calcium content. It is an immutable fact that pesticides negatively effect agricultural crops. And this influence is much more serious and varied than pesticide proponents believe. 

Fox DA, Katz LM. 1992. Developmental lead exposure selectively alters the scotopic ERG component of dark and light adaptation and increases rod calcium content. Vision Res 32 249-255. 

Kamitakahara, M., Kawashita, M., Miyata, N., Kokubo, T. and Nakamura, T. (2002) Bioactivity and mechanical properties of polydimethylsiloxane (PDMS)-CaO-Si02 hybrids with different calcium contents. Journal of Materials Science-Materials in Medicine, 13, 1015-1020. 

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