CHAPTER V 



THE STUDY OF GASES 



A. FIXED AIR AND INFLAMMABLE AIR 



Van Helmont recognises the existence of gases diffe- 

 ring from ordinary air. The fact that metals, insoluble 

 in most liquids, are dissolved by acids, was known and 

 used from very early times. The liberation of gases during 

 this process must have been noticed from the first, but it 

 was not until the latter part of the seventeenth century that 

 any attempt was made to collect and examine these volatile 

 products. Van Helmont (1577-1644), to whom we owe 

 the name of " gas," recognised the existence of a poisonous 

 GAS SYLVESTRE, i.e. " wood-gas," which possessed the power 

 of extinguishing a lighted candle ; he detected it in the air 

 of a cavern, in the fumes from a charcoal fire, and as a 

 product of the fermentation of wine and beer; he also 

 recognised what he thought to be the same gas as a product 

 of the action of nitric acid on silver, and of distilled vinegar 

 on chalk. In contrast to this, he found in the large intes- 

 tine, and as a product of the fermentation of dung, an 

 inflammable gas to which he applied the name GAS PINGUE. 

 The names used by van Helmont were applied broadly to 

 two types of gas, analogous with the " choke-damp " and 

 " fire-damp " of miners ; no attempt was made to distinguish 



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