Determination methods for four trace elements: iron, copper, zinc and manganese
Determination of iron, copper, zinc and manganese
Has anyone determined iron, copper, zinc and manganese? Come and exchange and learn together! I have a few questions and would like your advice!
1 Iron: How is the endpoint judged? The national standard says purple, but when I titrate, the purple only appears briefly, and after a slight swirl it is gone. If I titrate more, it is no longer purple; it seems darker than green, but it does not look like green either. I cannot say what color it is.
2 Manganese: The details are hard to control. I cannot manage the 220-240 degrees stated in the national standard, and every time the result is low.
3 Zinc: What points need attention? My result is also low, and I do not know the reason.
Teachers and colleagues, those with experience, please teach us!
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Practice brings true knowledge; you should still explore more in practice, and it will definitely help you.
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The endpoint of the iron determination is purple, but it will return in color. That is, when you titrate to purple, after swirling a few more times it will turn back to a greenish color, which shows that the endpoint has not been reached; it is just that the reaction speed is slow. Titrate until the color no longer fades and it is OK.
Although the manganese determination is hard to judge at 220-240 degrees, on the electric furnace do not let it boil violently; slight boiling is enough. Do you not also need to see white smoke coming from the conical flask? White smoke shows that the water has been evaporated, and only phosphoric acid remains in the conical flask; concentrated phosphoric acid gives off white smoke when heated. The heating degree only ensures that the water absorbs heat, becomes steam and evaporates out. If it really does not work, find a thermometer, or find a substance with a melting point of 220-240 and heat it to see how high the electric furnace must be set before it melts.
Just my humble opinion; I hope it can help you!
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xuexiele
intech-mxm added the following content on 2009-11-30 15:53
xuexiele
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What method are you using to determine it? Are you not using atomic absorption spectrometry?
1 Iron: How is the endpoint judged? The national standard says purple, but when I titrate, the purple only appears briefly, and after a slight swirl it is gone. If I titrate more, it is no longer purple; it seems darker than green, but it does not look like green either. I cannot say what color it is.
2 Manganese: The details are hard to control. I cannot manage the 220-240 degrees stated in the national standard, and every time the result is low.
3 Zinc: What points need attention? My result is also low, and I do not know the reason.
Teachers and colleagues, those with experience, please teach us!
--------------------------------------
Practice brings true knowledge; you should still explore more in practice, and it will definitely help you.
--------------------------------------
The endpoint of the iron determination is purple, but it will return in color. That is, when you titrate to purple, after swirling a few more times it will turn back to a greenish color, which shows that the endpoint has not been reached; it is just that the reaction speed is slow. Titrate until the color no longer fades and it is OK.
Although the manganese determination is hard to judge at 220-240 degrees, on the electric furnace do not let it boil violently; slight boiling is enough. Do you not also need to see white smoke coming from the conical flask? White smoke shows that the water has been evaporated, and only phosphoric acid remains in the conical flask; concentrated phosphoric acid gives off white smoke when heated. The heating degree only ensures that the water absorbs heat, becomes steam and evaporates out. If it really does not work, find a thermometer, or find a substance with a melting point of 220-240 and heat it to see how high the electric furnace must be set before it melts.
Just my humble opinion; I hope it can help you!
--------------------------------------
xuexiele
intech-mxm added the following content on 2009-11-30 15:53
xuexiele
--------------------------------------
What method are you using to determine it? Are you not using atomic absorption spectrometry?