I prepared the AgNO3 solution by dissolving the solid AgNO3 into ultrapure water (pH=4), but I observed some white turbidity as shown in the picture attached. The left is 100 mg/L solution and the right is pure water. Should the AgNO3 solution be clear and colorless? Why does my solution look turbid? Thanks!
Yes, it should be clear. You have a halogen (most likely chloride) present; this causes the formation of AgX, X being a halide.
I use the Milli-Q ultrapure water to make the solution, there should not be chloride in it.I tried to add HNO3 into the solution to lower the pH and even to the pH 2 the turbidity does not disappear. It is really confusing.
Mark and Baotong are correct. The turbidity is being caused by a colloidal suspension of AgCl particles in the water formed when the AgNO3 reacts with trace chloride in your "ultra pure" water. Silver chloride is so insoluble in water (0.002 g/L) that a saturated solution contains only about 1.3 x 10-5 moles of AgCl per liter of water.
Boroilicate glass i known to have traces of chloride. Using polyethylene and or triple rinsing all glassware and re-distilling your "ultra pure" water should help.
If the silver nitrate is left in sunlight (or any bright light), it breaks down (hydrolyses) to give black/brown silver oxide and nitric acid.
AgNO3 (aq) + H2O (l) --> AgO (s) + HNO3 (aq)
If stored in dark bottles and kept out of direct light, this reaction is minimised and the reacgent can be kept for quite a long time.
This effect of light on silver compounds is the basis of photography.
Dear colleagues.
I agree with Pf. Mirgorod. Along my PhD, I had the same problem with the AgNO3 solution. Just keep in dark in order to avoid the hydrolysis.
Regards
- Badges
- Science topic
- Similar topics
- Chemistry
- Nanotechnology
- Nanoparticle Research