Various precipitation examples for lead(II)
lead(II) nitrate O T R 61-62-8-20/22-33 S 53-17-45
potassium iodide solution
sodium carbonate solution
hydrochloric acid, 7%
sulphuric acid 10% Xi R 36/38 S (1/2)-26-30-45
sulphuric acid potassium dichromate solution T+ C N
R 21-25-26-35-37/38-41-43-46-49-50/53 S (1/2)-26-45-53-60-61
5 test tubes
- Safety goggles! All lead compounds are dangerous poisons! Caution with the dichromate solution! It is recommended that, in order to avoid a contamination of the working place, an easily cleaned pad is used when working with the lead salt.
- One places in each of the test tubes a small spatula-tipful of lead(II) nitrate and then adds about 1.5 ml of water. One carefully sways each test tube back and forth in order to dissolve the salt.
- One now adds to each test tube about 3 drops of the precipitation agent (potassium iodide solution, sodium carbonate solution, diluted hydrochloric acid, diluted sulphuric acid, sulphuric acid potassium dichromate solution).
- Characteristic precipitations are respectively formed (iodide, chromate - yellow, the others white). One precisely observes these: iodide is darker than chromate, only the chloride precipitation crystallizes well.
DisposalOne disposes of all residues as heavy metal waste. The poorly soluble precipitations must perhaps be in part removed mechanically (Caution! Gloves are recommended, otherwise wash the hands thoroughly after cleaning.).
Lead(II) forms many insoluble salts (brown to black sulfide is also of importance), and can therefore be easily verified, even if individual precipitations are not unambiguous.
Precipitations of CrO32-, CO32-, SO42-, Cl- , I- (from left to right)
Experiment based on own considerations