• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.10
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• pp.4069-4074
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• 2010

Phase change of calcium carbontae crystals in crystallization of precipitated calcium carbonate was researched by adding additives such as ethylenediaminetetraacetic acid(EDTA), diethylenetriaminepentaacetic acid(DTPA), citric acid(CIT) and pyromellitic amid(PMA). At low temperature $20^{\circ}C$, calcite crystal was made. At high temperature $80^{\circ}C$, aragonite crystal was made without additives. At middle temperature $40^{\circ}C$ and $60^{\circ}C$, Aragonite crystal also made by adding EDTA, DTPA. The crystal growth of Aragonite was retarded by the presence of CIT, PMA and the single phase of calcite was made. It was found that additives were important factors to make the single phase of calcium carbonate.

• Korean Journal of Agricultural Science
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• v.6 no.2
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• pp.185-191
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• 1979

Compressive and tensile strengths of commonly being used mortar and mortar specially hardened by adding 1%, 2% and 3% of $CaCl_2$ were compared under the different mixing ratio of mortar and ages to investigate the effect of $CaCl_2$ which is being used as a promotor for coagulation and hardness, on the strength of mortar. The results obtained were as follows: 1. The compressive strength of mortar hardened by addition of $CaCl_2$ was higher than that of commonly being used mortar. The highest compressive strength of mortar was obtained when 2% of $CaCl_2$ were added. 2. The tensile strength of mortar, which was made by adding $CaCl_2$ and aged for seven days, was higher than that of commonly being used mortar. The highest tensile strength of mortar was obtained when 1% of $CaCl_2$ was added and aged for 28 days. And the tensile strength of mortar with 2% of $CaCl_2$ was lower than that of commonly being used mortar. 3. When the amount of $CaCl_2$ added was higher than 3%, the mortar was abruptly hardened and thereby occurred crack was considered lowering strength of mortar. 4. The rich mix was effective for the increasing the compressive and tensile strength before seven days of age and less effective after seven days of age. Therefore, the addition of one to two per cent of $CaCl_2$ would be effective for promoting initial strength of mortar during winter season.

• Korean Chemical Engineering Research
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• v.59 no.1
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• pp.118-126
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• 2021

The experiments to produce the vaterite type calcium carbonate were conducted for using the waste oyster shell as the recycling resources. Firstly, the oyster shell were calcinated at 800 ℃ for 24 h. Calcinated oyster shell were reacted with the nitric acid solution, and were diluted to 0.1 M Ca(NO3)2 solution. This solution was mixed with 0.1 M Na2CO3 contained 0.1 mol lysine/1 mol CaO at 20 ℃ and 600 rpm mixing condition for 1 h. The reaction products were identified to vaterite type calcium carbonate (84.5% vaterite, 15.5% calcite) by XRD and SEM analysis. Mean particle diameter was 6.87 ㎛, and the lysine content in calcium carbonate was analyzed to 0.1%.

• Journal of Navigation and Port Research
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• v.39 no.6
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• pp.523-528
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• 2015

In this study, we investigated the effects of sulfuric acid on the synthesis of calcium borate in the artificial boron-containing brine (bittern) saturated with calcium hydroxide. For the study, we attempted to synthesize calcium borate under various conditions such as reaction temperature, reaction time, and cooling temperature after heating, and then to examine the recovery and purity of the calcium borate according to the presence or absence of sulfuric acid at each condition. The XRD analysis confirmed that, regardless of the presence of sulfuric acid, the calcium borate ($Ca_2B_2O_5{\cdot}H_2O$) was synthesized, while, in the presence of sulfuric acid, the calcium sulfate ($CaSO_4{\cdot}0.5H_2O$) was produced as a by-product. In all the experiments performed by varying the reaction temperature and time, the recovery and purity of the calcium borate without sulfuric acid were observed higher than those with it. The results indicated that the addition of sulfuric acid increased the solubility of the calcium hydroxide, but the calcium sulfate produced as a by-product could decrease the recovery and purity of the calcium borate by preventing the synthesis. In this study, the artificial boron-containing brine (bittern) (500 mg-B/L) was saturated with calcium hydroxide in the absence of sulfuric acid, and then the solution was heated at $80-105^{\circ}C$ for less than 10 minutes to synthesize the calcium borate. The recovery and purity of calcium borate were measured as high as 80 % and 96 %, respectively.

• Journal of the Korean Society of Food Science and Nutrition
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• v.36 no.9
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• pp.1188-1192
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• 2007

To provide functional properties in fish paste, boiled-dried anchovy [small size (SS) and large size (LS)] powder containing high amount of calcium was added at 0, 1, 2, 5, and 10% (w/w) levels. The properties of fried fish paste were evaluated by determination of sensory properties and physicochemical characteristics such as color, texture, folding test, and calcium contents. Calcium content of the fish paste increased with increasing anchovy amount. Increasing the amount of SS and LS in fish paste tended to decrease lightness, redness in Hunter color value, while increasing yellowness. All samples with 3 mm thickness had good flexibility and did not break even after 4 times folds. The fish pastes containing 10% of anchovy showed the highest values in strength, hardness, adhesiveness. In overall acceptance of sensory evaluation, SS and LS fish paste containing 1% and 2% of anchovy powder did not show any difference in comparison with control. These results suggest that SS and LS anchovy powder can be applied to fried fish paste products to allow for high calcium contents.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.35 no.6
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• pp.601-607
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• 2002

The present study was designed to examine how sea tangle intake contributes to the content of bone calcium and breaking force of femur with growing female rats. Weaned rats were fed on experimental diets consisting in four levels of sea tangle powder; $0\%$ (control), $0.5\%$, $1.0\%$ and $1.5\%$ for 4 and 8 weeks. Body weight gain and feed intake were not significantly affected by added amount of sea tangle. Bone breaking strength, ash content and calcium levels of the femur of rats fed on diets with sea tangle were higher than those of control groups (p<0.05). But moisture content weight and length of femur did not show any significant difference among groups. TP, ALB, TC, TG, AIP, osteocalcin, GOT and GPT levels in serum did not show any significant difference through the total feeding period but calcium and phosphorus contents of serum increased with increase in feeding period, significantly in $0.05\%$ level by added amounts of sea tangle. Calcium levels in feces increased significantly (P<0.05), but ash levels were not changed significantly by added amount of sea tangle. We could expect from this results that the ingestion of sea tangle (Kjellemaniella crassifolia) could be helpfull to increase bone calcium content and calcium absorption as well as to intensify the femur stength and to increase the calcium content of rats.

• Journal of the Korean Society of Food Science and Nutrition
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• v.32 no.2
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• pp.161-166
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• 2003

This study attempted to fortify Kimchi with water extracts of shells of shellfishes (corb shell, short neck clam, taste clam, ark shell, top shell, oyster) as natural resource of calcium. Kimchi added with the shell extracts in 5% were fermented at 1$0^{\circ}C$ with measurements in chemical, microbiological and sensory qualities. Calcium content of shellfish shells before water extraction was in the range of 25.57~38.78%. Kimchi added with the extracts showed higher pH, lower acidity, lower total aerobic bacterial count and higher lactic acid bacteria count compared to control Kimchi without any addition. After 7 day fermentation the Kimchi added with the extracts also showed higher ash and calcium contents compared to control products (3.3~5.0 vs. 2.8~3.0% and 300~376 vs. 70~95 mg%). Kimchi with oyster shell extract gave the most pronounced effect in ash and calcium contents. The addition of extract made Kimchi crisper and less sourer oganoleptically. In the overall acceptability, the Kimchi fortified with the shell extracts were better than control after 14 day fermentation.

• The Journal of the Korea Contents Association
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• v.2 no.1
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• pp.120-124
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• 2002

It is the purpose of the present to report result of a preliminary electrochemical characterization of the as-cast Mg-Ca alloys. Electrochemical data will be correlated with chemical composition of impurities, and the microstructural change before and after Ca is added. This paper shows that small addition of Ca imparts beneficial effect in electrochemical properties of Mg alloy, primarily, through microstructural modifications.

• Journal of the Korean Society of Food Science and Nutrition
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• v.31 no.3
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• pp.428-432
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• 2002

Calcium-enriched powder was investigated for use as an ingredient in kimchi formulation to retard the fermentation rate and to fortify the nutritional quality of kimchi. The calcium powder was added to salted Chinese cabbage in the concentrations of 0.5, 1.0 and 1.5%, and then stored at 10$\^{C}$. Quality characteristics of kimchi such as pH, titratable acidity, reducing sugar content and microbial loads were measured during fermentation. After a lag period of 2 days, pH and reducing sugar abruptly decreased until 10 days, and then attained to stabilized levels, while acidity increased steadily for 20 days. Addition of calcium powder with 1.5% retarded the change rates of pH and acidity, showing the slowest chance and the highest final pH. Kimchi added with calcium powder maintained a higher reducing sugar content during the whole fermentation period of 25 days. Kimchi samples which were added with 0.5% and 1.0% of calcium powder and fermented at 10$\^{C}$ for 7 days showed better sensory scores in aroma and taste than the other samples.

• Korean Journal of Food Science and Technology
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• v.25 no.6
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• pp.596-601
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• 1993

Changes of textural properties of garlic pickle was studied during aging at room temperature with or without skin or addition of $CaCl_{2}$. The alcohol insoluble solids(AIS) was gradually decreased by aging. The decreasing rate of AIS was less for those of unpeeled and $CaCl_{2}-added$ pickles. In pectic substances, HSP was a little decreased and HXSP was significantly increased and HWSP and total pectin was changed little. The $CaCl_{2}-added$ pickles showed higher HSP and lower HXSP than those of $CaCl_{2}-not$ added pickles. The hardness of unpeeled pickles was slightly higher than peeled pickles and of $CaCl_{2}-added$ pickles was higher than $CaCl_{2}-not$ added pickles and decreased generally during aging for all samples.