Ash content,InorganicIt can be the residue after calcination or the residue after drying.But the ash must be in some substancesolidPartial rather thanGasorliquidpart.At high temperature, a series of physical andChemical changeFinally, the organic components volatilize and dissipate, while the inorganic components (mainlyinorganic saltAnd oxides), and these residues are called ash.
When the food is burned at high temperature, a series of physical andChemical changeFinally, the organic components volatilize and dissipate, while the inorganic components (mainlyinorganic saltAnd oxides), and these residues are called ash.It indicates the total amount of inorganic components in foodindex。
Generally speaking, ash refers to total ash (i.eCoarse ash）It contains the following three types of ash:
3. Acid insoluble ash: trace amounts of contaminated sediment and foodSilicon oxideEtc.
It is the oxide of various mineral elements.Main elements include Ca, Mg, K, Na, Si, P, S, Fe, Al, I, etc. In additiontrace elementThe total number is no less than 60.Analyze the plant ash to know what inorganic nutrients are contained in the plant.Peat ash, i.epeatContained inmineral, expressed as the percentage of solid matter in peat.Most of the minerals in peat are brought by wind and water, and a few are from plant residues.The former is calledextraneous ash , the latter is calledIntrinsic ash（Pure ash）, both collectivelyTotal ash。The total ash content of peat in China is relatively high, ranging from 30% to 50%, of which the pure ash content only accounts for about 6% to 15%, which varies slightly depending on the external ash content and the types of carboniferous plants.Silicon content is the highest among the main components of ash.If the peat contains more calcium, iron and aluminum, it is of great use value.
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Ash in paper
Generally, there is no special requirement for the ash content in the raw materials of paper.But in the production of electrical insulation paper, the ash must be removed to meet certain quality requirements.In grass raw materials, especially straw with high ash content, SiO in ashtwoThe content of is high, which causes difficulty in alkali recovery.It is an unsolved problem to reduce or eliminate the interference of silicon in alkali recovery.
Ash is an inorganic salt in plant fiber raw materials, mainlypotassium、sodium、calcium、magnesium、sulfur、phosphorus、siliconSalts of.
Paperyash contentThere are: ash content of fiber itself and additional ash content（talcEtc.).The ash content of paper refers to the amount of inorganic matter in the paperMechanical propertiesIt has a great impact.On the premise of ensuring normal use, the ash content of offset printing paper should be limited as far as possible. If the ash content is too large, it is very easy to produce dust shedding during printing, and the rubber blanket will be stained, which will affect the printing quality of printed products.In addition, the paper breaking lengthFolding enduranceWith the increase of paper ash content.
The ash content of paper can be measured with reference to ISO 2144, Tappi T 211 and T 413, as well as the national standard GB463-1989-T "Determination of ash content of paper and board".
botany
Ash: dried plant tissue is burned at 600 ℃, and carbon, hydrogen, oxygen, nitrogen and other elements in organic matter are lost to the air in the form of carbon dioxide, water, molecular nitrogen and nitrogen oxides. The remaining nonvolatile gray white residues are called ash.Various minerals exist in the ash in the form of oxides, sulfates, phosphates, silicates, etc. The elements constituting the ash are called ash elements.They come directly or indirectly from soil minerals, so they are also called mineral elements.[1]
Total ash refers to the amount of mineral, inorganic salt or other impurities in the foodorganic compoundAfter burning and oxidation, the residual white matter is weighed to get the total ash weight.
In oil
Ash content refers to,sampleInorganic matter obtained by calcining the residue after burning, expressed in mass percentage.
Physical meaning: Ash has different concepts for different oil products. For base oil or oil products without metal salt additives, ash can be used to judge the refining depth of oil products. The less the better. For oil products (new oil) filled with metal salt additives, ash can be used as a means to quantitatively control the amount of additives added. At this time, the less the ash, the better,It should not be lower than a certain value or range.
Measurement standard: GB/T508-85 "Ash test of base oil" (mostly used for ash verification of base oil or oil products without metal salt additives);GB/T 2433-88 "Additives and lubricating oils containing additives Determination of sulphated ash".
In coal
Coal ash refers to the residue left after complete combustion of coal.Almost all of these residues come frommineral。Minerals in coalThere are three sources:
1. Primary minerals -- inorganic elements contained in coal forming plants;
2. Secondary minerals -- minerals mixed with or associated with coal during coal formation;
3. Foreign minerals -- minerals mixed in coal mining and processing.
measurecoalThe ash content in is generally used:raw coalAsh and floating coal ash.Raw coal, flotationAsh contentIt is represented by Ad% symbol.The ash content of coal in China is generally high and varies greatly.The ultra-low ash coal with ash content less than 10% only accounts for about 17% of the proven reserves in China.
The ash content of coal is an index that plays an important role in the research of coal quality characteristics and utilization.In general,Minerals in coalIt is not conducive to the processing and utilization of coal. The lower the content, the better. Because the coal ash is the thermal decomposition of minerals in coalresidueTherefore, it can be used to calculate the mineral content in coal.The higher the ash content of coal,Available carbonThe lower the content of.Ash content of coal and other characteristics of coal, such as element compositionCalorific value、Slagging property、activityandGrindabilityAnd so on.In addition, because the determination of ash in coal is simple, and the distribution of minerals in coal is often uneven, the sampling and preparation of coalSample methodIn the research, the ash content is generally used to evaluate the methodAccuracyAnd precision.In coal washingCoal washingAsh content is used as an index to evaluate the washing effect.[2]
Significance of measurement
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1. The total ash content of food is an important basis for controlling the quality of finished or semi-finished food products.For example, the content of total ash in milk is constant.Generally, it is 0.68%~0.74%, and the average value is very close to 0.70%. Therefore, the method of determining the total ash in milk can be used to determine whether the milk is adulterated. If water is added, the ash content will be reduced.In addition, the concentration ratio can also be judged. If the measured milk ash is about 1.4%, it means that the milk is concentrated twice.It is also like rich and strong flour. Wheat contains high ash content in bran, while endospermproteinIf the content is high, the ash content of bran is 20 times higher than that of endosperm, which means that the ash content is low if the precision in flour is high.
2. Evaluate whether the food is hygienic and contaminated.If the ash content exceeds the normal range, it indicates that unreasonable hygiene standards have been used in food production.If there are impurities in the raw materials or some sediment is mixed in the processing, it can be detected when measuring the ash content.
3. Judge whether the food is adulterated.
4. Reference indicators for nutrition evaluation (various elements can be measured).
Determination method
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[Total ash determination method] The test sample used for determination must be crushed so that it can pass through the No. 2 sieve. After mixing evenly, take 2~3g of the test sample (3~5g of the test sample can be taken if acid insoluble ash must be measured), place it in a crucible that is ignited to constant weight, weigh it (accurate to 0.01g), burn it slowly, pay attention to avoid burning, and gradually raise the temperature to 500~600 ℃ when it is fully carbonized,Ash completely to constant weight.Calculate the percentage of total ash in the test article according to the weight of residue.
If the test article is not easyashingThe crucible can be cooled, 2ml of water or 10% ammonium nitrate solution can be heated to wet the residue, and then the residue can be evaporated on a water bath. The residue can be ignited as before until the contents of the crucible are completely incinerated.[3]
[Determination of acid insoluble ash] Take the ash obtained in the above item, carefully add about 10ml of dilute hydrochloric acid into the crucible, cover the crucible with a watch glass, heat it on a water bath for 10min, rinse the watch glass with 5ml of hot water, incorporate the washing solution into the crucible, and useAshless filter paperFilter, and wash the residue in the crucible on the filter paper with water until the washing solution is not visiblechlorideReaction,Filter residueMove it with filter paper to the same crucible, dry it, and ignite it to constant weight.Calculate the acid insoluble ash content (%) of the test article according to the weight of the residue.[3]
