Oxygen 257 



test with blue litmus solution as in the previous 

 experiment. 



EXPERIMENT 116. Burn a small piece of phosphorus 

 in another jar, carefully observing all the precautions 

 mentioned in Experiment 78 during the handling of 

 the substance. After the jar has cooled, shake up with 

 water and test with litmus as in the two last described 

 experiments. 

 Equations : 



Sulphur + oxygen = sulphur dioxide. 

 (Sulphur + oxygen = sulphur trioxide.) 

 Phosphorus + oxygen = phosphorus pentoxide. 



175. As a common result of the testing with blue 

 litmus solution in Experiments 114, 115, and 116 it will 

 have been noticed that the products of the combining 

 of the three elements, carbon, sulphur, and phosphorus, 

 with oxygen all possess, when dissolved in water, the 

 power of turning blue litmus red. Similar observations 

 were made by Lavoisier. Bodies which have this 

 property are termed "acids", so he gave the name 

 " oxygen " (from Greek, oxus, sharp or acid, and gennao, 

 to produce) to the gas which he thought was a charac- 

 teristic constituent of all acids. We now know that 

 his idea is incorrect, but we retain the name oxygen for 

 the gas. 



EXPERIMENT 117. Sodium is a peculiar metal which 

 is kept in bottles containing paraffin oil in order to 

 protect the metal from the oxygen of the air. Remove 

 a small piece, not larger than a pea, with dry crucible 

 tongs from a bottle and place it on some dry filter- 

 papers on a dry bench. Absorb the greater part of the 

 adhering oil by gentle pressure with the papers and 

 put the sodium into a dry deflagrating spoon. Avoid 



H. D. 8. 17 



