CHAPTER VIII 



Water 



59. Chemical Composition. That water is composed 

 of hydrogen and oxygen in approximately the proportion 

 of 2 volumes of H to i of O can be demonstrated by pass- 

 ing a current of electricity through water and collecting 

 the escaping gases. Oxygen will be 

 liberated at the positive electrode, 

 while hydrogen will be liberated at the 

 negative electrode. That water is 

 composed of 16 parts, by weight, of 

 oxygen, to 2 parts, by weight, of 

 hydrogen, can be demonstrated by 

 passing hydrogen gas over copper 

 oxid heated in a tube. The reaction 

 which takes place is CuO + 2H = 

 H 2 O + Cu. If suitable provisions are 

 made for weighing the oxid of copper 

 used, and the water produced, it will 

 be found that the weight of the 

 water bears a definite relation to the oxid of copper 

 reduced. For every loss of 16 grams of oxygen 

 from the copper oxid, 18 grams of water are produced, 

 showing that water is eight-ninths, by weight, oxygen. 

 Experiment 8. Distillation of water. Connect flask A (Fig. 

 29) with the bent tube B to the condensing apparatus issued 

 for this experiment. Place the distilling flask upon the sand- 

 bath and in position as shown in Fig. 29. Fill the tank of the 

 distilling apparatus, and half fill the flask, with water. Apply 



Fig. 28. Electrolysis 

 of water. 



