Magnesium oxide is an inorganic compound with the chemical formula of MgOoxide, is a kind ofIonic compound, white solid at room temperature.Magnesium oxidePericlaseIt exists in nature and is the raw material for magnesium smelting.
Magnesium oxide has high fire resistance and insulation performance.It can be transformed into crystals after being burned at a high temperature above 1000 ℃, and become dead burned magnesium oxide (magnesia) or sintered magnesium oxide when it rises to 1500 - 2000 ° C.
Magnesium oxide is an alkaline oxide, which has the general property of alkaline oxide and belongs to cementitious material.It is white or grayish white powder, odorless, tasteless, non-toxic, and is a typical alkaline earth metal oxide, chemical formula MgO.The melting point is 2852 ℃, the boiling point is 3600 ℃, and the density is 3.58g/cmthree（25℃）。Soluble in acid and ammonium salt solution, insoluble in alcohol.The solubility in water is 0.00062 g/100 mL (0 ° C), 0.0086 g/100 mL (30 ° C).Exposed to the air, it is easy to absorb water and carbon dioxide and gradually becomes basic magnesium carbonate. Light products are faster than heavy products. They combine with water to generate magnesium hydroxide under certain conditions, showing a slightly alkaline reaction. The pH of saturated aqueous solution is 10.3.Soluble in acid and ammonium salt, insoluble in water, its solution is alkaline.Insoluble in ethanol.It has strong refraction in the visible and near ultraviolet light range.Magnesite (MgCOthree）, dolomite (MgCOthree·CaCOthree）And seawater are the main raw materials for magnesium oxide production.Thermal decomposition of magnesite or dolomite yields magnesium oxide.The hydrated lime is used to treat seawater to get magnesium hydroxide precipitation, and the magnesium hydroxide is burned to get magnesium oxide.The magnesium chloride brine block obtained from the comprehensive utilization of seawater or the brominated brine can also be used as raw materials, and sodium hydroxide or sodium carbonate can be added to generate magnesium hydroxide or basic magnesium carbonate precipitation, and then magnesium oxide can be obtained by burning.China mainly uses magnesite, dolomite, brine or brine block as raw materials[1]。
Product category
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Classification: pointsLight magnesium oxideandHeavy magnesium oxideTwo.Light weight, loose volume, white amorphous powder.Odorless, tasteless and non-toxic.Density 3.58g/cmthree。It is insoluble in pure water and organic solvents, and its solubility in water increases due to the presence of carbon dioxide.It is soluble in acid and ammonium salt solutions.It is transformed into crystal after high-temperature burning.Generated when encountering carbon dioxide in the airMagnesium carbonateDouble salt.The heavy weight is compact, white or beige powder.Easy to combine with water, easy to absorb water and carbon dioxide when exposed to air.AndMagnesium chlorideSolution mixing is easy to gel and harden.
With the industrial upgrading and the demand and development of high-tech functional material market, a series of high-tech fine magnesium oxide products have been developed and produced, which are mainly used for advanced lubricating oil, advanced tanning alkali extraction, food, medicine, silicon steel, advanced electromagneticHigh purity magnesium oxideIt is composed of nearly ten varieties.
Industrial grade light burning
Application field: mainly used in the production of magnesite products.Light burned magnesiaIn combination with magnesium chloride solution in a certain proportion, it can be gelled and hardened into a hardened body with certain physical and mechanical properties, which is called magnesite cement.As a new type of cement, magnesite cement has the advantages of light weight, high strength, fire protection, heat insulation, energy conservation and environmental protection, and can be widely used in building materials, municipal, agricultural, machinery and other fields.According to WB/T1019-2002 Light burned magnesia for magnesite products, the chemical composition of light burned magnesia is:
Brand
QM-85
QM-80
QM-75
level
Superior products (A)
First class product (B)
Qualified products (C)
MgO ≥
eighty-five
eighty
seventy-five
Active MgO ≥
sixty-five
sixty
fifty
Free CaO ≤
one point five
two
two
Loss on ignition
1-9
1-9
≤12.0
High grade lubricating oil
Application field: mainly used as cleaner, vanadium inhibitor and desulfurizer in the processing of advanced lubricating oil, which can greatly improve the compactness and rheology of lubricating film and reduce ash content.Lead removal and mercury removal can reduce the environmental pollution of lubricating oil or fuel waste. The magnesium oxide after surface treatment can also be used as a complexing agent, chelating agent and carrier in the refining process, which is more conducive to product fractionation and improving product quality.Especially, the addition of Mg0 during heavy oil combustion can eliminate the damage of vanadium acid in heavy oil to the furnace.
Food grade
Application field: It is used as food additive, color stabilizer, pH regulator as a supplement of magnesium in health products and food.It can be used as decolorizing agent, ice cream powder, PH regulator, etc. when refining granulated sugar.As an anti caking agent and antacid, it is used in wheat flour, milk powder chocolate, cocoa powder, grape powder, sugar powder and other fields, as well as in ceramics, enamel, glass, dyes and other fields.
Medical grade
Application field: medical grade magnesium oxide can be used as an antacid, adsorbent, desulfurizer, lead remover, complexing filter aid, PH regulator in the field of biological pharmacy. It can be used as an antacid and laxative medically to inhibit and alleviate excessive gastric acid and treat gastric ulcer and duodenal ulcer disease.Neutralizing gastric acid is strong, slow and lasting, and does not produce carbon dioxide.
Silicon steel grade
Application field: silicon steel grade magnesium oxide has good magnetic conductivity (that is, it has a large positive susceptibility) and excellent insulation performance (that is, the conductivity can be as low as 10-14us/cm dense state).It can form a good insulating layer and magnetic conductive medium on the surface of silicon steel sheet, so as to restrain and overcome the eddy current and skin effect loss (iron loss for short) of silicon steel core in transformer.It can improve the insulation performance of silicon steel sheet and be used as a high temperature annealing isolating agent.It can also be used as ceramic materials, electronic materials, chemical raw materials, adhesives, additives, etc. in silicon steel, used as dephosphorizing agent, desulfurizer, and insulating coating generator.
Advanced electromagnetic level
Application field: wireless high-frequency paramagnetismpermeability magnetic material, magnetic rod antenna, magnetic core of FM element, etc.Replace ferrite.It can be used in the production of composite superconducting magnetic materials, as well as in the electronic magnetic industry.Work“Soft magnetic material”。It is also an ideal raw material for industrial enamel and ceramics.
High purity magnesium oxide
Application: High purity magnesium oxide has excellent alkali resistance and electrical insulation at high temperature.Coefficient of thermal expansionAnd high thermal conductivity with good light transmittance.It is widely used as high-temperature and heat-resistant materials.Raw materials used as transparent ceramic crucibles, substrates, etc. in the ceramic field are used as fillers for magnetic devices, insulating materials, and various carriers in electrical materials, electrical fields.The thermal conductivity of ceramic substrate is more than 2 times higher than that of alumina, and the loss of electrolyte is only 1/10 of that of alumina.It can also be used as high purityFused magnesiaIt can be used as "analytical pure" magnesium oxide chemically.
Nanometer scale
Application field: nanometer magnesium oxide has obviousSmall size effect, surface effectquantum size effect It has many special functions and important application values in optics, catalysis, magnetism, mechanics, chemical industry, etc. It has a very broad prospect and is an important new material in the 21st century.Nano magnesium oxideIt is widely used in electronics, catalysis, ceramics, oil products, coatings and other fields.It plays different roles in different products. It is used as flame retardant in chemical fiber and plastic industries;Adhesives and additives in silicon steel sheet production, such as high temperature water repellent, advanced ceramic materials, electronic industrial materials, and chemical raw materials;Radio industry high-frequency magnetic rod antenna, magnetic device filler, insulating material filler and various carriers;Refractory fibreAnd refractory materials, magnesia chrome bricks, fillers for heat-resistant coatings, high-temperature resistant, insulation resistant instruments, electrical, cable, optical materials and steelmaking;Electrical insulator materials, manufacturing crucibles, furnaces, insulated conduits (tubular elements), electrode bars, electrode sheets.
In the textile field, with the high performanceFlame retardant fibreWith the increasing demand for flame retardants, the synthesis of new high-performance flame retardants provides an ideal material for the development of functional fabrics.Nanometer magnesium oxide is often used together with wood chips and shavings to manufacture lightweight, sound insulation, heat insulation, refractory fiberboard and other refractory materialscermet。Compared with some traditional phosphorus or halogen containing organic flame retardants, nanometer magnesium oxide is non-toxic, tasteless, and has a small amount of addition. It is an ideal additive for developing flame retardant fibers.In addition, nanometer magnesium oxide has a strong ability to clean and inhibit corrosion when used in fuel oil, and has a good application prospect in coatings.
Feed grade
Adding 50~90 grams of magnesium oxide or 0.5% of concentrate daily to the dairy cow diet can not only supplement the magnesium deficiency in the diet to prevent the occurrence of magnesium deficiency, but also is an excellent rumen buffer, which can regulate rumen fermentation, increase the absorption of breast milk to the precursors of milk synthesis, and increase milk production and milk fat rate.According to relevant foreign reports, adding 0.5% magnesium oxide to the concentrate supplement of dairy cows can increase the milk yield by 1.6 kg on average, increase the milk fat rate by 0.145 percentage points, and help to increase the feed intake.?The addition of magnesium oxide in the diet of dairy cows can prevent heat stress. Magnesium ion can work together with sodium ion and potassium ion to maintain the balance of osmotic pressure inside and outside the cells, alleviate the reaction of dairy cows to heat stress, thus improving the intake of dairy cows in summer and maintaining the milk yield.In addition, it is suggested that in the case of heat stress, the amount of magnesium oxide in the diet should be increased to compensate for the loss of magnesium in the body, so as to ensure and maintain normal milk production.Cows and beef cattle have good balance mechanism to deal with excessive magnesium ions, so properly increasing the amount of magnesium oxide will not cause adverse effects on cattle.
The symptoms of magnesium deficiency in dairy cows are: firstly, the appetite of dairy cows is decreased, the action is slow, and the cows are lethargic. With the aggravation of the disease, the cows become stiff and wobbly. In addition, the cows become nervous and irritable, and their muscles tremble obviously. If they continue, the cows are completely paralyzed and convulsive.If not treated in time, death will result.In addition, magnesium deficiency will reduce the digestibility of nutrients and lead to a decline in milk production of cows.
When ruminants such as cattle and sheep graze, they must ensure that their food contains enough magnesium to prevent them from convulsions due to lack of magnesium.This convulsion is usually caused by cows or sheep eating magnesium deficient forage in cold weather.There are two common ways to add magnesium in livestock feed: one is to mix magnesium powder with syrup and add it to the feed;The other is to add light burned magnesium powder directly into the purchased feed.Magnesium deficiency is more common in beef cattle and sheep than in cows, because there is more concentrate in the diet of cows and less concentrate in the diet of beef cattle and sheep.
The addition amount of magnesium oxide in ruminant diet is 0.5%~1.0%.
poultry
Newborn chicks can only survive for a few days when fed a diet that is completely magnesium deficient.When feeding low magnesium diet, chicks grow slowly, lethargy, asthmaShortness of breath, after being frightened, they will show short-term convulsions, and finally lead to temporary coma or death.According to the experiment, the growth rate of broilers fed a diet containing 200 ppm magnesium was 80% lower than that fed a diet containing 600 ppm magnesium.
For laying hens, the egg production will decline rapidly when magnesium is deficient.Low blood magnesium causes extensive use of bone magnesium, smaller eggs, lighter eggshell weight, and lower magnesium concentration in yolk and eggshell.Studies have proved that the thicker the eggshell, the higher the magnesium concentration in the eggshell, which indicates that properly increasing the magnesium concentration in the diet of laying hens can improve the quality of the eggshell and increase the egg weight.
Generally, in production, the magnesium concentration of commonly used poultry feed is between 0.15% and 0.22% according to age, variety and poultry.
pig
Due to the continuous improvement of pig breeds and productivity, the nutritional needs of magnesium should be increased accordingly.The lack of magnesium ion will greatly increase the mortality of piglets.The lack of magnesium will lead to the treading disease of pigs, which is manifested by repeatedly lifting the rear hooves when the pigs stand as if they were treading in situ.For sows, magnesium oxide is widely used as a laxative to prevent stress syndrome such as excessive sensitivity and tail biting in captive pigs.
Recent studies have also shown that adding magnesium oxide to the diet of pigs or properly increasing the concentration of magnesium in the diet can improve the quality of pork.Growing finishing pigs fed diets supplemented with magnesium oxide can improve growth rate and pork quality, including PH value and color of pork, and reduce PSE pork.
According to different growth stages, body weights and production purposes, the concentration of magnesium in pig feed commonly used in feed industry is 0.13%~0.27%.
freshwater fish
Freshwater fish need to supplement magnesium in feed due to insufficient dissolved magnesium in water.
Rumen buffer regulators in additives, such as:sodium bicarbonate, magnesium oxide, etc
single crystal
Single crystal magnesium oxide refers to a colorless and transparent crystal with MgO content of 99.95% or more, which has extremely strong high and low temperature resistance (high temperature 2500 ℃, low temperature - 270 ℃), corrosion resistance, insulation, good thermal conductivity and optical properties.The main parameters are as follows:
molecular weight
forty point three one one
density
3.65 g/cmthree
Thermal expansion coefficient (× 10-7/℃）（25℃）
one hundred and thirty-eight
Thermal conductivity (cal/cm/sec/℃) (25 ℃)
zero point zero six
Specific heat (cal/g. ℃)
zero point two zero nine
Mohs hardness
five point five
Refractive index
one point seven four
application area
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The annual output of magnesium oxide in China is about 12 million tons.
It is used to determine sulfur and arsenic in coal, pyrite and steel.Used as a standard for white pigments.Light magnesium oxide is mainly used to prepare ceramicsenamelRaw materials of refractory crucible and refractory brick.Also used as polishing agents, adhesives, coatings, and paperfiller，NeopreneAnd fluororubberacceleratorAnd activator.After mixing with magnesium chloride and other solutions, magnesium oxide water conditioner can be made.In medicine, it is used as an antacid and laxative, for gastric hyperacidity and duodenal ulcer, and as a catalyst and raw material for magnesium salt manufacturing in the chemical industry.It is also used for glass, dyeingPhenolic plasticManufacturing of etc.Heavy magnesium oxide is used in rice milling industry for firing, grinding and half drum.Construction industryUsed for manufacturing artificial chemical floor, artificial marble heat shield, sound insulation board, plastic industryFiller。It can also be used to produce other magnesium salts.
One of the main uses of magnesium oxide is asFlame retardantUse of traditionalFlame retardant materialsThe flame retardant mixture composed of halogenated polymers or halogenated flame retardants is widely used.However, in case of fire, due to thermal decomposition and combustion, a large amount of smoke and toxic corrosive gas will be generated, which will hinder fire fighting, personnel evacuation, and corrosion of instruments and equipment.In particular, it is found that more than 80% of fatal accidents in fires are caused by thick smoke and toxic gases generated by materials. Therefore, in addition to flame retardant efficiency, low smoke and low toxicity are also indispensable indicators of flame retardants.The development of flame retardant industry in China is extremely unbalanced,Chlorine flame retardantThe proportion is high, ranking first among all flame retardants, among whichChlorinated paraffinOccupy a monopoly position.However, chlorine flame retardants release toxic gases when acting, which is far from the non-toxic and efficient pursuit of modern life.Therefore, in order to comply with the development trend of low smoke, low toxicity and pollution-free flame retardants in the world, the development, production and application of magnesium oxide flame retardants are imperative.
Production method
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Double decarbonization method
Double decarbonization method
In order to improve the extraction rate of magnesium oxide and reduce the energy consumption of products.To improve product quality and increase product variety, the double subtraction carbonization process mainly changes the carbonization conditions and subtracts the production process with high energy consumption.The purified lime emulsion is carbonized under specific conditions to dissolve 80-90% MgO and generate a supersaturated solution of light magnesium carbonate containing 20-30 g/L MgO.After rapid pressure filtration, the basic magnesium carbonate can be resolved from the saturated solution of light magnesium carbonate at 20-30 ℃ under specific conditions.The basic magnesium carbonate filter cake contains only 50-60% water.The light magnesium oxide product is obtained through calcination.
The process features: (see the process flow chart for details)
(1) The extraction rate of magnesium oxide increased by 20-30%.
(2) The compression and pyrolysis processes are subtracted, and the moisture content of basic magnesium carbonate filter cake is reduced by 25-30%.
Therefore, the coal consumption per ton of light magnesium oxide products is reduced by 75%, and the power consumption is reduced by 65%.
Gas phase method
The high-purity magnesium oxide powder is prepared by reacting high-purity metal magnesium with oxygen to form crystal nucleus, and then making the particles continue to grow.Raw materials containing more than 80% (weight) of magnesium oxide are dissolved with inorganic acids (sulfuric acid, hydrochloric acid, nitric acid) in a molar ratio of 1:2 to produce magnesium salts of inorganic acids.The impurities are refined and removed, and then pressurized and heated under oxygen atmosphere. After water washing, dehydration, drying, and heating at 1100 ℃ for 1h, high-purity magnesium oxide is prepared.
Magnesium hydroxide calcination method:Magnesium sulfate solutionAs the raw material, pure ammonia water is used as the precipitator to add magnesium liquid to precipitate Mg (OH)two, viaPlate and frame filter pressConduct solid-liquid separation and wash the filter cake to obtain high-purity Mg (OH)twoAfter drying and calcining, high-purity magnesium oxide is obtained.
Calcination method: The bitter earth powder is separated by water and precipitated into magnesium slurry after removing impurities, and then the magnesium hydroxide is dehydrated to form magnesium oxide through digestion, drying and calcination:
MgO+HtwoO→Mg(OH)two
Mg(OH)two→MgO+HtwoO
Calcination method
Magnesite is calcined in a calciner at 950 ℃, and then cooled, screened and crushed to produce light burned magnesium oxide.
In the soda ash method, first dilute the bittern with water to about 20 ° Be and add it into the reactor, slowly add about 20 ° Be of clarified soda solution under stirring, and then react at about 55 ℃ to generate heavy magnesium carbonate. After rinsing, centrifugal separation, roasting at 700~900 ℃, crushing and wind separation, light magnesium oxide products are prepared:
Dolomite is calcined, digested and carbonized to obtain basic magnesium carbonate, and then through thermal decomposition, calcination, crushing and wind separation to obtain light magnesium oxide.
Ammonium bicarbonate method
With the ammonium bicarbonate method, the mother liquor (magnesium ion content is about 50g/L) after salt making from seawater is mixed with ammonium bicarbonate in proper proportion after impurities are removed, precipitation reaction is carried out, and then centrifugation, drying, calcination, crushing, grading and packaging are carried out to obtain light magnesium oxide products:
The dolomite or magnesite is calcined, digested with water, carbonated, calcined and crushedActive magnesium oxide。The brine dolomitic lime method uses seawater or brine as raw material to precipitate with lime or white cloud ash. The obtained magnesium hydroxide precipitate is filtered, dried, and calcined to produce active magnesium oxide.Bitter earth powder sulfuric acid ammonium bicarbonate method reacts magnesium containing raw materials such as bitter earth powder with sulfuric acid to generate magnesium sulfate solution, whose MgO+HtwoSOfour→MgSOfour+HtwoO Magnesium sulfate solution andAmmonium bicarbonateReaction to generate magnesium carbonate precipitation, and its MgSOfour+NHfourHCOthree+NHthree→MgCOthree↓+(NHfour)twoSOfourThen the precipitate is filtered, washed, dried, calcined and crushed to produce active magnesium oxide.
Sintering process
The raw material is fused magnesium block.After material selection, crushing and screening, it is mixed with a certain proportion of liquidtitaniaAfter full mixing, washing, drying and sintering, the particle size of 40~150 is screened out, which is the finished high-temperature electrical grade magnesium oxide.
Brine ammonium bicarbonate method
The basic magnesium carbonate is produced by the reaction of brine and ammonium bicarbonate, and then aged, washed, dehydrated, dried, calcined, crushed, purified and heat treated to produce silicon steel grade magnesium oxide.
Electrofusion
The finished product is made from high-purity magnesium oxide by electric melting.
Hydrochloric acid method
The leftovers from the production of heavy magnesium oxide are sent into the reactor, and hydrochloric acid is added for reaction to generate magnesium chloride hexahydrate. Then sodium carbonate is added for reaction to generate basic magnesium carbonate, which is washed with water. The basic magnesium carbonate is calcined at high temperature, cooled and crushed to produce magnetic magnesium oxide.
Pharmacopoeia information
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source
The content of MgO in this product shall not be less than 96.5% when it is burned to constant weight.
character
This product is white powder, odorless, tasteless, and can slowly absorb carbon dioxide in the air.
This product is almost insoluble in water, insoluble in ethanol, and soluble in dilute acid.
identify
Identification reaction of magnesium salt in dilute hydrochloric acid solution of this product (general rule 0301).
inspect
alkalinity
Take 1.0g of this product, add 50mL of water, boil it for 5min, filter it while hot, wash the filter residue with appropriate amount of water, incorporate the washing solution into the filtrate, add a few drops of methyl red indicator solution, and then add 2.0mL of sulfuric acid titrant (0.05mol/L), the solution will change from yellow to red.
Color of acid solution
Take 1.0g of this product, add 15mL of acetic acid and 5mL of water, boil it for 2 minutes, cool it, add water to make it 20mL. If it is turbid, it can be filtered, and the solution should be colorless. If it develops color, it should not be deeper than the yellow green No. 2 standard colorimetric solution (General Rule 0901 Method 1).
calcium oxide
Take 5.0g of the newly ignited and cooled product, add 30mL of water and 70mL of acetic acid to dissolve it, boil for 2 minutes, cool it, filter it, wash the filter residue with dilute acetic acid, combine the filtrate and lotion, place it in a 100mL measuring flask, dilute it with dilute acetic acid to the scale, shake it up, use it as the test solution, accurately measure 10mL, add 300mL of water, add 10mL of triethanolamine solution (3 → 10) and 10mL of 45% potassium hydroxide solution,Place for 5 minutes, add 0.1g of calcein indicator, titrate with ethylene diamine tetraacetic acid disodium titrant (0.01mol/L) until the solution turns from purplish red to blue, and correct the titration result with blank test.Every 1mL of EDTA disodium acetate titrant (0.01mol/L) is equivalent to 0.5608mg of CaO. The calcium oxide content of this product should not exceed 0.50%.
chloride
Accurately measure 1mL of the test solution under calcium oxide, dilute it with water to 25mL, and check according to the law (general rule 0801). Compared with the control solution made of 7.0mL of standard sodium chloride solution, it should not be more concentrated (0.14%).
sulfate
Accurately measure 2mL of test solution under calcium oxide, dilute it with water to 20mL, check according to the law (general rule 0802), and it shall not be more concentrated (0.3%) than the reference solution made of 3.0mL of standard potassium sulfate solution.
carbonate
Take 0.10g of this product, add 5mL of water, boil it, cool it, add 5mL of acetic acid, and do not boil it.
Insoluble matter in acid
Take 2.0g of this product, add 75mL of water, and then add a small amount of hydrochloric acid in several times. Stir as you add it until it no longer dissolves. Boil it for 5 minutes, filter it, and wash the filter residue with water until the lotion no longer shows the reaction of chloride. Burn it to constant weight, and the residual residue should not exceed 2.0mg (0.10%).
Soluble substance
Take 1. Og of the product, add 100ml of water, boil it for 5 minutes, filter it while hot, evaporate the filtrate on a water bath, and dry it at 105 ° C for 1 hour. The residual residue shall not exceed 2.0%.
Loss on ignition
Take 0.50 of this product, burn it to constant weight, and the weight loss shall not exceed 5.0%.
ferric salt
Take 50mg of this product, add 2mL of dilute hydrochloric acid and 23mL of water to dissolve it, and then check according to the law (general rule 0807). Compared with the control solution made of 2.5mL of standard iron solution, it should not be deeper (0.05%).
Manganese salt
Take 1.0g of this product, add 20mL of water, 5mL of nitric acid, 5mL of sulfuric acid and 1mL of phosphoric acid, heat and boil it for 2 minutes, cool it, add 2.0g of potassium periodate, boil it for 5 minutes, cool it, transfer it into a 50mL colorimetric tube, dilute it to the scale with non reducing water (add 3mL of nitric acid and 5g of potassium periodate per 1000mL of water, boil it for 2 minutes, cool it), shake it well,It shall not be deeper (0.003%) than 0.30mL of standard manganese solution (0.275g of anhydrous sulfuric acid ignited at 400~500 ° C to constant weight, put into a 1000mL volumetric flask, add appropriate amount of water to dissolve and dilute to the scale, and shake up. Every 1mL is equivalent to 0.10mg of Mn).
heavy metal
Take 0.50g of this product, add 10mL of dilute hydrochloric acid and 5mL of water, heat and dissolve it, boil it for 1 minute, cool it, filter it, add 1 drop of phenolphthalein indicator solution to the filtrate, add an appropriate amount of ammonia test solution to the solution until it turns light red, add 2mL of acetate buffer solution (pH 3.5) and an appropriate amount of water to make it 25mL, add 0.5g of ascorbic acid to dissolve it, check according to law (General Rule 0821, the first method), and compare the color at 5 minutes,The content of heavy metals shall not exceed 40 parts per million.
Arsenite
Take 0.40g of this product, add 5mL of hydrochloric acid and 23mL of water to dissolve it, and check according to the law (the first method of general rule 0822), which should meet the requirements (0.0005%).
Assay
Take 0.5g of this product, weigh it precisely, add 30mL of sulfuric acid titrant (0.5mol/L) to dissolve it, add one drop of methyl orange indicator solution, titrate it with sodium hydroxide titrant (1mol/L), and subtract the amount of sulfuric acid that should be consumed by the mixed calcium oxide (CaO) according to the amount of sulfuric acid consumed, that is, the amount of sulfuric acid consumed by MgO in the test amount.Every 1mL of sulfuric acid titrant (0.5mol/L) is equivalent to 20.15mg of MgO or 28.04mg of CaO.
