11. The addition of which compound to solution is BEST for making silver iodide soluble? A. Ammonia B. Sodium thiosulfate C. Potassium cyanide D. Sodium sulfide C is the best answer.The complex ion of silver that is most soluble in water also enhances the solubility of silver iodide the most. From Table 1, we learn that silver cyanide makes the most soluble complex ion (the cyanide is a strong ligand). This narrows the choice down to potassium cyanide as the best compound for making silver iodide more soluble. The best answer is C. Hi, I'm having trouble understanding why the cyanide is better at making the Ag cation. Is it because it's a better leaving group vs thiosulfate? Thanks.