问题
问答题 简答题
根据《土壤全氮测定法半微量开氏法》（NY／T53-1987），在测定土壤中包括硝态及亚硝态氮的全氮时，样品消煮前加入了什么试剂？各起什么作用？
答案
参考答案：
先加入高锰酸钾将样品中的亚硝态氮氧化成硝态氮后，再用还原铁粉使全部硝态氮还原，转化成铵态氮。
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根据《土壤全氮测定法半微量开氏法》（NY／T53-1987），在测定土壤中包括硝态及亚硝态氮的全氮时，样品消煮前加入了什么试剂？各起什么作用？
参考答案：
先加入高锰酸钾将样品中的亚硝态氮氧化成硝态氮后，再用还原铁粉使全部硝态氮还原，转化成铵态氮。
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geography, physics, chemistry and math: Others go to school to leam a skill so that they can make money. But no one can leam everything from school. A teacher, no matter how much he knows, cannot teach his 2______ everything they want to know. His job is to help his students know how to learn. He teaches them how to read and how to 3______. So, much more is to be learnt 4______ school by the students themselves. It's always more 5______ to leam how to study by oneself than to memonze some facts or rules. Great scientists, like Newton, Galileo and Edison, didn't get 6______ from school, but they were all successful. They invented so many things. The reason for their success is that they knew how to study. They read books that were not 7______ at school. They worked hard all their lives, wasting not a single moment. Above all, they knew how to use their brains. |