# Lead nitrate and sodium iodide [closed]

As we know that if you mix lead nitrate and sodium iodide solutions together, a yellow precipitate forms. Can you maybe add nitrate in water that may or may not have lead in it and then mix it with a sodium iodide solution and get the same results if lead was present in the water?

First, the iodide precipitates with lead ions, $$\ce{Pb+}$$, called cations because of the positive charge. It doesn't matter what the anions are in solution, whether nitrate, acetate or other, so there's no need to add nitrates or nitric acid for this test.
Second, yes, this is a test for lead in solution, but it is not at all sensitive. At room temperature, about 0.75 g of the product, lead iodide or $$\ce{PbI2}$$, could dissolve in a liter of water. That means that there could be a fatal amount of lead in water, yet that wouldn't be enough to form a yellow precipitate. One approved test for lead in drinking water is an atomic absorption (AA) spectrophotometer.