Potassium iodide and silver nitrate are used to make silver(I) iodide, which is used for high speed photographic film and for cloud seeding:

  
    
      
        
          
            KI
            
              
                (
                aq
                )
              
            
            
              
            
          
          

          
          +
          9
          
          
            AgNO
            
              3
              
                (
                aq
                )
              
            
            
              
            
          
          ⟶
          
            AgI
            
              
                (
                s
                )
              
            
            
              
            
          
          

          
          +
          
            KNO
            
              3
              
                (
                aq
                )
              
            
            
              
            
          
        
      
    
    {\displaystyle {\ce {KI_{(aq)}{}+ 9AgNO3_{(aq)}-> AgI_{(s)}{}+ KNO3_{(aq)}}}}

Organic chemistry
KI serves as a source of iodide in organic synthesis.
Commercially available iobenguane is labeled with iodine-123, and product labeling recommends administration of potassium iodide 1 hour prior to administration of the radiopharmaceutical for all age groups, while the European Association of Nuclear Medicine recommends (for iobenguane labeled with either isotope), that potassium iodide administration begin one day prior to radiopharmaceutical administration, and continue until the day following the injection, with the exception of new-borns, who do not require potassium iodide doses following radiopharmaceutical injection.Product labeling for diagnostic iodine-131 iobenguane recommends potassium iodide administration one day before injection and continuing 5 to 7 days following administration, in keeping with the much longer half-life of this isotope and its greater danger to the thyroid. Iodine-131 iobenguane used for therapeutic purposes requires a different pre-medication duration, beginning 24–48 hours prior to iobenguane injection and continuing 10–15 days following injection. Nuclear accidents
In 1982, the U.S. Food and Drug Administration approved potassium iodide to protect thyroid glands from radioactive iodine involving accidents or fission emergencies. In an accidental event or attack on a nuclear power plant, or in nuclear bomb fallout, volatile fission product radionuclides may be released. Of these products, 131I (Iodine-131) is one of the most common and is particularly dangerous to the thyroid gland because it may lead to thyroid cancer. By saturating the body with a source of stable iodide prior to exposure, inhaled or ingested 131I tends to be excreted, which prevents radioiodine uptake by the thyroid.