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278 September, 1970 IR3 as a source of air pollution or subsequent water pollution. A silver-iodide generator and an automobile engine are similar in size and fuel consumption rate. Both re lease unfiltered combustion products to the free air close to the ground. Examination of automobile exhaust reveals many materials which are sub- stantial contributors to air pollution. Two of these materials, carbon monoxide and lead halides, present potential and actual toxic hazards. The inoffensive nature of the effluent from a silver-iodide generator is emphasized by this comparison. APPENDIX I.-PROPERTIES ~~ A standard type propane-acetone silver iodide generator operating at an output rate of 6 g of AgI per hr will burn: 1 gal of propane; 6 g AgI; and 3 g ,\ NaI. Acetone is solvent for AgI and NaI, and is quantity-dependent upon solution concentration. The ratio of NaI to AgI (1: 2) has been selected as typical for a 2 % AgI- acetone solution. If a higher percentage solution of AgI in acetone is desired, the ratio of NaI to AgI may be increased, the effect of which would be to in- .1',.. crease the concentration of iodides in the acetone solution. Data on iodine dis- sociated from acetone solutions of higher than 2 % AgI which will not recombine and remains as iodine vapor were not available. It is assumed that the propane is completely oxidized and that all of the oxygen available in the air is used, in which: C3 He + 5 O2 - 3 CO2 + 4 H20; 1 gal of propane = 1,905.5 g; Oxygen required = 6,930.5 g; Air is 23.14 % oxygen (by weight); Air required to supply 6,930.5 g of oxygen = 30,000 g; 1 cu m air = 1,293 g; and Volume of air weighing 30,000 g = 23.2 cu m. To be conservative, the amount of oxygen (and air) required to oxidize the acetone is not considered. It is often assumed that the AgI and NaI are dissociated in the flame and are subsequently recombined in the form of AgI, and AgI-NaI complexes. The possibility of hazard lies in amount of iodine which does not recombine and remains as iodine vapor. A preliminary study made at Colorado State Univer- sity revealed the upper limit of this value to be on the order of 5 %. On an hourly basis: 6 g AgI, 54.05 % I = 3.24 g Ii 3 g NaI, 84.65 % I = 2.54 g I; 5.78 g, rounded to 5.8 g; and 5 % dissociation of 5.8 g = 0.29 g I as vapor per hr. With 23.2 m3 air used per hour for combustion of the propane, the maximum concentration of iodine vapor in the flame which will not recombine is 12.5 mg per cu m. Assuming a flame temperature of 2,3000 F, further dilution will occur as ambient air is mixed with the flame materials. An individual might expose himself to the generator effluent when its temperature is relatively warm. An effluent temperature of 1500 F was arbitrarily selected as the maximum tem- perature which might be tolerated for a short period of time. This temperature would be encountered within 5 ft of the flame. While the specific heat of the flame materials and air are slightly different, for simplicity, they are assumed to be the same, and the following expression