294 Domestic Science 



to permit fish to remain alive, and, unless the cold 

 weather be excessively prolonged in duration, the water 

 in lakes and ponds, except where they are extremely 

 shallow, does not all become solid. 



Exercise for Student. 



From what has been already stated, investigate what would 

 happen in very cold weather, if water did not possess a point of 

 maximum density. 



Thus, if a liquid be pure water, it must, in addition 

 to complying with the requirements of the tests given 

 in the list above, exhibit the property of abnormal 

 expansion between the temperatures and 4. 



203. The question of the exact composition of 

 water has been the subject of many careful investiga- 

 tions. To determine the relation by weight between 

 the quantities of hydrogen and oxygen present in a given 

 amount of water, we may synthesise that compound 

 as described in the next experiment. 



EXPERIMENT 137. A steady gentle stream of 

 hydrogen is required in this experiment. This may 

 best be obtained by the electrolysis of water as pre- 

 viously described. An alternative method, in which 

 the hydrogen produced is of a lesser degree of purity, 

 is afforded by the use of a "Kipp's generator". This 

 is illustrated in Fig. 98. The middle bulb of the 

 apparatus should be filled about one-third full with 

 scraps of the purest zinc foil obtainable. Open the 

 tap at the side of this bulb and pour down the opening 

 of the topmost bulb a mixture of pure hydrochloric 

 acid and water in equal proportions. When the 

 lowest bulb is full of the liquid, close the tap and then 

 pour in more acid until the top bulb is about one-third 

 full. The apparatus is now ready for use. Open the 



