34 



AGRICULTURAL CHEMISTRY 



enabling the oxygen to be given off more easily. The change 

 which takes place is expressed by the equation: KC1O 3 KC1 -f 36. 

 The products of the reaction are potassium chlorid and oxygen. 



Fig. 16. Preparation of oxygen, using sink in place of pneumatic trough. 

 The oxygen is collected in the cylinders, while the potassium chlo- 

 rid remains with the manganese dioxid in the test-tube. 



37- Properties of Oxygen. Physically considered, 

 oxygen is a colorless, odorless, and tasteless gas, about 

 1 6 times as heavy as hydrogen. It is slightly soluble in 

 water, and, when subjected to a low temperature and a 

 high pressure, it is liquefied. Chemically, oxygen unites 

 with all common elements to form oxids. It is not com- 

 bustible, but is a supporter of combustion. When the 

 burning splinter was thrust into the cylinder of oxygen, 

 the carbon and hydrogen of the wood united wdth the 

 oxygen in the cylinder, forming carbon dioxid and water. 

 When substances unite with oxygen they are oxidized, 

 that is, oxygen is added to the material. An oxid is a 

 compound of oxygen and any other element. When sul- 

 fur is burned, it unites with oxygen, forming sulfur di- 



