A freshly precipitated $\mathrm{Fe}(\mathrm{OH}){}_3$ is converted into a stable sol by shaking it with a small amount of $\mathrm{FeCl}{}_3$ solution. This process and the origin of charge are best described as:

1. Adialysis; the particles adsorb $\mathrm{Cl}{}^{-}$ ions and become negatively charged
2. Bpeptization; the particles adsorb $\mathrm{Fe}{}^{3+}$ ions and become positively charged
3. Ccoagulation; the particles adsorb $\mathrm{Fe}{}^{3+}$ ions and become positively charged
4. Dpeptization; the particles adsorb $\mathrm{Cl}{}^{-}$ ions and become negatively charged