Lead dioxide candle

Lead dioxide candle A device for determining the amount of sulfur dioxide in the air. The SO, reacts with a film of lead dioxide to produce lead sulfate, which is measured to determine the concentration. Leakage The rate of fluid loss from an enclosure due to a pressure difference between the inside and outside of the enclosure. 

There are two accepted methods for determining the sulfur dioxide (SO2) concentration in the atmosphere of interest. Both employ the affinity of lead oxide for sulfur dioxide. The most common technique uses sulfation plates. This procedure is covered in dqtail in ASTM G 91, Test Method for Monitoring Atmo heric SO2 Using the Sulfation Plate Technique. These devices are no longer available for purchsise, but must be prepared in the laboratory. The second method is the peroxide candle, similar in its function to the chloride candle. The procedure suggests a 30-day exposure, followed by a standard sulfate analysis. This procedure is covered by ASTM D 2010, Test Methods for Evaluation of Total Sulfation Activity in the Atmosphere by the Lead Dioxide Technique. In both cases, the results are calculated as the capture rate of SO2 per unit area, normally per m. ... 

He continued his experiments and discovered even more new gases sulfur dioxide, silicon fluoride, ammonia gas, and nitrogen. However, his most important discovery was oxygen. In June 1774 Priestley got a burning lens with a diameter of 12 inches and immediately began to experiment with it. In one experiment he turned the lens on mercury calx (mercuric oxide) and obtained an air in which candles burned more brightly than they did in ordinary air. At first he did not know what to make of this result, so he continued experimenting. He soon found that he could get the same gas from certain other materials, such as lead oxide. 

---