Determination of iron, copper, zinc and manganese

Have you determined iron, copper, zinc and manganese? Let's exchange and study. I have a few questions for your advice! 1 Iron: how to determine the end point? The national standard says purple, but when I titrate it, it only shows for a moment, and then shake it up a little bit, and then it's not purple, it seems to be deeper than green, and it's not like green, so I can't say any color. 2 Manganese: the details are difficult to control. Can not master the national standard of 220-240 degrees, each time the result is low. 3 Zinc: what do you need to pay attention to? The result page of my work is low. I don't know why. Teachers and colleagues, come and teach us with experience. It will certainly help you to learn from practice or to explore more in practice. The end point of iron determination is purple, but it will turn back, that is, when you titrate to purple. A few more shakes will change back to green, indicating that he just reacts slowly before reaching the finish line, and he will ok until the color does not fade. Although the determination of manganese is not easy to judge 220-240 degrees, but do not boil violently on the electric stove, just boil slightly, don't you still want to see white smoke coming out of the triangle bottle? White smoke means that the water has been evaporated, there is only phosphoric acid in the triangle bottle, and the heating of concentrated phosphoric acid will produce white smoke. The degree of heating is only to ensure that the water absorbs heat and evaporates into steam. If it really doesn't work, find a thermometer, or heat it with a substance with a melting point of 220-240 and see how big the electric stove is before it melts. A little humble opinion, I hope I can help you! Xuexieleintech-mxm at 15:53 on 2009-11-30 15:53 add the following content xuexiele-- what method did you use to measure it, didn't you use atomic absorption spectrometry?