How to test the ingredients of warmer?
(1) Take a small amount of sample (take the black mixture after warmer is used), add water to dissolve it, there are a lot of insolubles. Filter to obtain a colorless and transparent filtrate. The filtrate was divided into four parts.
Phenomenon
● The KSCN solution was added to the first filtrate, and there was no obvious phenomenon.
● The AgNO3 solution was added to the second portion, and a white precipitate appeared.
● NaOH solution was added dropwise to the third part, and there was no obvious phenomenon.
● The fourth part is a flame reaction, and the flame is yellow.
Conclusion
It shows that the sample can be partially dissolved, the product contains NaCl, and the filtrate after dissolving in water does not contain Fe3+, Al3+, Mg2+.
 
(2) Take another small sample, add excess HCl solution, and filter to obtain a golden yellow clear filtrate. The filtrate was divided into two portions.
● Add one portion of KSCN solution, and the solution immediately turns blood red.
● Add NaOH solution dropwise to the other portion. At first, there is no obvious phenomenon. Adjust the pH of the solution to 7 with pH test paper, so that the NaOH solution neutralizes the remaining HCl solution. Continue to add NaOH solution dropwise, and dark green precipitation gradually began to appear, shaking, and the precipitation disappeared. Continue to add NaOH solution dropwise to excess, the precipitated part disappeared and turned brownish yellow. Let stand for layering, the upper layer is a colorless and transparent solution, and the lower layer is a reddish-brown precipitate. Filter and heat the obtained solid to obtain a reddish-brown solid. The solid is insoluble in water but dissolves in acid to obtain a brown-yellow solution, which is initially determined to be Fe2O3 .