When H2O2 (Hydrogen-Peroxid) is added to EIS (one or two drops per glass of EIS), it will be noted that there is an immediate clearing effect. The Tyndall (what you see if you shine a laser pointer though the liquid) will become very faint as well. If the ppm of the EIS is sufficiently high (25 to 30 ppm) a white cloudy precipitate may form as well.
There are a number of reactions that occur. H2O2 (Hydrogen-Peroxid) is normally thought of as an oxidizer, but it can act as a reducer as well. Also silver is considered a catalyst for H2O2, but in actuality gets directly involved in the reactions.
The H2O2 reacts with the silver particles, producing ionic silver, a combination of silver hydroxide and silver oxide. This makes the large particles disappear, reducing the tyndall. However H2O2 also reacts with the silver oxide and silver hydroxide producing a 2 atom colloid of silver plus oxygen (and water in the case of silver hydroxide). Over time this 2 atom colloidal particle can end up being converted back to silver oxide and silver hydroxide, and so forth. The final result is a mixture of ionic silver (hydroxide and oxide) and very small colloidal particles. Thus if you add H2O2 to freshly made EIS, you can sometimes see the oxygen bubble off, and the tyndall may change significantly. But more importantly, the particulate portion of the EIS will go from being medium or large particles to many more very small particles, and the particle content will increase from a typical 5-15% to around 30-50%. If you have a strong tyndall from large particles, it will decrease, and if you have a weak or no tyndall it will increase with the formation of the 2 atom particles. This enhances absorption, as well as effectiveness. Note that it is recommended to let the EIS sit for 5 or more minutes after adding the H2O2 to let it stabilize. Also some experts recommend letting EIS age for 2 or more days before adding the H2O2, and experiments by me indicate a more consistant effect if this is done. For some images of the effect H2O2 has on silver particles see Hydrogen Peroxide and Colloidal Silver Micrographs