求翻译：称取风干土样0.3000g，放于50ml离心管中，加入0.3M柠檬酸钠20ml、1M重碳酸钠2.5ml水浴加热至80℃后加连二亚硫酸钠0.50g，不断搅拌维持15min。冷却后离心分离，将浸提液转入250ml容量瓶，重复一次，最后用1MNaCl洗涤离心管2次，洗涤液转入同一容量瓶，定容后采用等离子发射光谱仪（VISTA-MPX）测定铁、铝含量[12]是什么意思？

Said to take air-dried soil samples 0.3000g, put in a 50ml centrifuge tube, add citric acid, sodium 20ml 0.3m, 1m sodium bicarbonate 2.5ml water bath heated to 80 ℃ after the dithionite 0.50g, stirring constantly to maintain 15min. Cooled centrifuge, the extract transferred to a 250ml volumetric fla

Samples of the soil from drying on the 0.3000 G, 50 ml centrifuge tube, add 0.3 M citric acid and 20 ML, 1 ml 2.5 M sodium carbonate as well as re-heats up to 80 after the degrees C sodium laureth sulfate derived from the 2 0.50 G, 15 min of continuous agitation. After cooling, the centrifugal liqui

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Take the air dry clay-like 0.3000G, in 50ml in the centrifuge tube, add 0.3M 2.5ml sodium carbonate sodium citrate 20ml, 1M water bath heated to 80 degrees centigrade and even two sodium sulfite after 0.50g, constantly stirring to maintain 15min. After cooling the centrifugal separation, will extrac

The name takes air seasoning soil sample 0.3000g, puts in the 50ml centrifuge tube, joins 0.3M sodium citrate 20ml, 1M the sodium bicarbonate 2.5ml heating in water bath to 80℃ add-on sodium hydrosulfite 0.50g, stirs unceasingly maintains 15min.After cooling the centrifugal separation, changes over