GB 2760-96: processing aids, GMP.
FAO/WHO (1984): butter and whey cream, 2g/kg (only used for adjust Ph value, calculate on anhydrous substance); grape juice and its concentrated juices (physical method for anticorrosion) baby food, edible caseinate, according to GMP.
In Japan, the maximum amount is 1.84% (calcium 1%).
1. Calcium hydroxide Used for preparing bleaching powders, hard water softeners and the disinfecting and clarifying agents of tap water , as well as in building industry
2. Used for pharmacy. Used as rubber and oil industry additives. Used in lubricants for preventing coking, sludge deposition and anti-corrosion. Used as hard water softeners, disinfectants, antacids and so on.
3. Used as analytical reagents, carbon dioxide absorbents, as well as in organic synthesis
4. Used for making bleaching powder, hard water softener, depilatory, disinfectant, acid stop agent, astringent and various calcium salts.
5. Use for carbon dioxide examination and gas absorption. Used for leather hair removal, insecticide and water treatment.
The nitroparaffins, nitromethane, nitropropane, etc. form salts with inorganic bases such as Calcium hydroxide . The dry salts are explosive [Chem. Eng. news 30:2344 1952]. Bases are chemically similar to sodium hydroxide (NaOH) or sodium oxide (Na2O). They neutralize acids exothermically to form salts plus water. When soluble in water they give solutions having a pH greater than 7.0. Mixing these materials with water can generate troublesome amounts of heat as the base is dissolved or diluted. Bases react with certain metals (such as aluminum and zinc) to form oxides or hydroxides of the metal and generate gaseous hydrogen. Bases may initiate polymerization reactions in polymerizable organic compounds, especially epoxides). They may generate flammable and/or toxic gases with ammonium salts, nitrides, halogenated organics, various metals, peroxides, and hydroperoxides. Materials of this group often serve as catalysts. A strong base. Forms caustic solution in water [Merck 11th ed. 1989].
Lime slaking method: first calcine limestone into calcium oxide, and the selected calcium oxide is slaked with water by the ratio of 1: (3~3.5). Then the generated calcium hydroxide solution is purified and separated to remove slag, and then centrifuged for dehydration. After further dried at 150~300℃, the above products is screened (120 mesh or more) to obtain the finished calcium hydroxide.
CaCO3 → CaO + CO2↑
CaO + H2O → Ca(OH) 2
Air & Water Reactions
Water soluble. The amount of heat generated by hydrolysis may be large.
Accurately weigh about 1.5g of sample into a beaker and then gradually add 30ml of dilute hydrochloric acid (TS-117). After the sample is fully dissolved, transfer the mixture into a 500ml volumetric flask. Flush the beaker and transfer the lotion into the volumetric flask too. Then dilute to the mark with water and mix fully. Take 50.0ml of the above solution into an appropriate container and add 50.0ml of water. Add in turn 30ml of 0.05ml/L disodium EDTA, 15ml of sodium hydroxide solution (TS-224) and 300mg hydroxynaphthol blue indicator with a 50ml burette under stirring (preferably with a magnetic stirrer), and then continue titrating to the blue end. Per mL of 0.05 ml/L of EDTA disodium corresponds to 3.705 mg of calcium hydroxide.
Heat analytical grade calcium carbonate at 1000o during 1hour. Allow the resulting oxide to cool and add slowly to water. Heat the suspension to boiling, cool and filter through a sintered glass funnel of medium porosity (to remove soluble alkaline impurities). Dry the solid at 110o and crush it to a uniformly fine powder. [Ehrlich in Handbook of Preparative Inorganic Chemistry (Ed. Brauer) Academic Press Vol I p 934 1963.]
In mortar, plaster, cement and other building and paving materials; in lubricants, drilling fluids, pesticides, fireproofing coatings, water paints; as egg preservative; manufacture of paper pulp; in SBR rubber vulcanization; in water treatment; dehairing hides.
Solubility in water (g/100ml)
Dissolved grams in 100 ml of water at different temperatures (° C):
0.189 g/0°C; 0.182g/10°C; 0.173 g/20°C; 0.16 g/30°C; 0.141g /40℃
8.6 x 10-2g/80 °C; 7.6 x 10-2g/90 °C
fine white powder
Mix the sample with 3 to 4 times amount of water to form a uniform paste. Stand for clarification and the transent supernatant is alkaline for the litmus test.
Mix 1g of the sample with 20 ml of water, and add sufficient acetic acid to form solution. The calcium salt test (IT-10) is positive.
ADI no restricting (FAO/WHO, 2001).
LD50 7300 mg/kg (mouse, oral).
Corrosive, weaker than lime.
GRAS (FDA, §182.1205, §184.1205, 2000).
The dust or suspension droplets of calcium hydroxide have a stimulating effect on the mucous membrane, which can cause sneezing and coughing. As alkali, it can also saponify the fat, absorb water from the skin, dissolve protein, as well as stimulate and corrode the organization. Moreover, the inhalation of lime dust may cause pneumonia.
The maximum allowable concentration of calcium hydroxide is 5 mg/m3. Once Inhaling dust, people can inhale water vapor, codeine and Judah auning, or paint mustard cream at the chest; when calcium hydroxide coming into the eyes, people should rinse the eyes as soon as possible with the running water and followed by 5% ammonium chloride solution or 0.01% CaNa2-EDTA solution, and then add 0.5% tetracaine solution dropwise. While working, people should wear dustproof fiber work clothes, gloves and dust-proof glasses to protect the respiratory organs, and paint grease ointment to prevent dust inhalation.
Dust irritates eyes, nose and throat.
Odorless white granules. Sinks in water.