OXYGEN. 



75 



or substances suffering decomposition. For instance : 100 pounds of oxygen 

 may be obtained from how many pounds of potassium chlorate, or from how 

 many pounds of manganese dioxide ? 



The molecular weight of potassium chlorate is found by adding together the 

 weights of 1 atom of potassium = 39 + 1 atom of chlorine = 35.4 + 3 atoms 

 of oxygen = 48 ; total = 122.4. Every 122.4 parts by weight of potassium 



FIG. 6. 



Apparatus for generating oxygen. 



chlorate liberate the weight of 3 atoms, or 48 parts by weight, of oxygen. If 

 48 are obtained from 122.4, 100 are obtained from 255. 



48 : 122.4 : : 100 : x 



x = 255. 



In a similar manner, it will be found that 813.7 pounds of manganese dioxide 

 are necessary to produce 100 pounds of oxygen. Mn0 2 = 54.8 -f 32 = 86.8. 

 3MnO 2 = 3 X 86.8 = 260.4. Every 260.4 parts furnish 2 X 16 = 32 parts of 

 oxygen. 



32 : 260.4 : : 100 : x 



x = 813.7. 



Physical properties. Oxygen is a colorless, inodorous, tasteless 

 gas ; up to a few years ago it was looked upon as a permanent or 

 stable gas, as all attempts to liquefy or solidify it had failed. Lately, 

 however, these efforts have been successful, and oxygen has been con- 

 verted (though in small quantities) into a colorless liquid by the 

 application of a pressure of 470 atmospheres at a temperature of 

 _130 C. (202 F.) 



Oxygen is but sparingly soluble in water (about 3 volumes in 100 

 at common temperature). A litre of oxygen under 760 mm. pressure, 

 and at the temperature C. (32 F.), weighs 1.4298 grammes. 



