COMMON THINGS. WATER. 



rectangular tube with a glass vessel containing water, placed 

 upon a charcoal fire, or supported over a spirit lamp. The other 

 end, 6, communicates by a bent tube, bed, with a glass tube filled 

 with water, inverted and immersed in a capsule or dish containing 

 water. The water is supported in the tube, as in the former expe- 

 riments, by the atmospheric pressure. If gas issue from the 

 mouth of the tube, d, which is bent under that of the wide tube 

 containing the water, this gas will rise in bubbles, displacing the 

 water in the top of the tube. 



These arrangements being made, and the iron contained in the 

 tube, a 6, being rendered red-hot, the water in the glass vessel is 

 made to boil. The vapour proceeding from it entering the tube 

 a b at a, forces its way through the interstices of the red-hot iron 

 wire; there it is decomposed, the iron attracting the oxygen, 



Fig. 4. 



with which it combines, forming a substance called the oxide of 

 iron, which is familiarly known as rust. The hydrogen alone 

 issues from the tube at 6, and passing through bed rises into 

 the large tube, displacing the water, as represented in the figure. 



When a sufficient quantity of gas is collected, its weight is ascer- 

 tained, and also the increase of weight imparted to the iron wire in 

 the tube, a 6, by the oxygen which has been combined with it, and it 

 is always found that the latter is exactly eight times the former. 



Thus we still find the same remarkable fact reproduced in 

 various forms. The rusted wire is heavier than the original 

 clean wire by the weight of the oxygen which it has attracted 

 from the aqueous vapour, and which, combining with it, forms 

 the rust; and this weight is eight times that of the hydrogen 

 from which it has been separated, showing as before that water 

 consists of 8 parts by weight of oxygen and 1 of hydrogen. 

 112 



