Final answer:
Distilled water is used to wash lead iodide in order to avoid introducing any additional ions that could contaminate the compound, ensuring its purity for uses such as fabricating X-ray and gamma-ray detectors.
Step-by-step explanation:
Distilled water is used to wash lead iodide mainly because it is free of ions that could otherwise react with the lead iodide. In chemistry, it's important to use distilled water for washing precipitates like lead iodide (PbI2) to ensure that no additional ions are introduced that could affect the purity of the compound.
Lead iodide is a bright yellow solid that was formerly used as an artist's pigment, known as iodine yellow, and has properties that make it useful for the fabrication of X-ray and gamma-ray detectors.