Burning lens

In addition, Lavoisier and his colleagues introduced programmatically into the chemical laboratory apparatus other than the furnace, the crucible, and the retort, describing and illustrating the new instruments construction and their use in texts like Lavoisier s Traite elementaire de chimie. Lavoisier employed not only the balance and the thermometer but pneumatic apparatus, the electrical machine, the burning lens, and the calorimeter. 80 As the instruments of the chemical laboratory proliferated, so, too, did the problems chemists dreamed of posing and resolving. 

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. 

In October 1772 Lavoisier performed some experiments using a large burning lens owned by the Academy of Sciences. He found that when litharge (an oxide of lead) was heated with charcoal, large quantities of air were released. Of course it wasn t air at all—it was carbon dioxide. At the time, Lavoisier was unaware that carbon dioxide—or fixed air as it was then called—has properties very different from ordinary air. He was also unaware that Priestley had experimented with numerous different airs and had shown that atmospheric air has more than one component. Lavoisier also performed experiments that showed that sulfur and phosphorus also gain weight when they are burned. Marie Anne wrote up the results... 

Figure S3 The burning lens was made for the Academy of Sciences in 1774. A similar lens was used by Lavoisier in 1772 to heat diamonds and also a mixture of lead oxide and powdered charcoal...

FIGURE 1.4 Focusing on combustion The great burning lens belonging to the Academy of Sciences. Lavoisier used a similar lens in 1777 to show that a mixture of calx (metal oxide) and charcoal released a large volume oi fixed air when heated. 

Fig. 2.1 The Burning Lens used by Averani and Targioni. Donated by its maker, Benedikt Bregans of Dresden, to Grand Duke Cosimo III in 1690. Courtesy Museo Galileo, Florence Photography Franca Principe...

Averani and Targioni, in demonstrating the combustible nature of diamond, as weU as determining its nature, debunked the belief that this gem was absolutely unassailable diamond exists in a form that is thermodynamically unstable at ambient conditions. The chemistry laboratory of the Museum, with its advanced scientific tools, became a research center of considerable importance for the naturalists of the time. For example, the aforementioned burning lens was used again in 1814, by Humphry Davy (1778-1829), when he came to Florence with his valet and laboratory apprentice Michael Faraday (1791-1867), to complete further research on the cherrrical natirre of diamond. 

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