Hygiene as Nature Study 



F. AI. Gregg, 



V. A Study of Water. 



It is not to be expected that pupils in the fourth and fifth 

 grades shall figure in a campaign to improve the water supply 

 of a community, but there is a good deal of valuable information 

 that can be given them in such an impressive way as to make it 

 accrue to their own personal health, and, in time, to the very 

 great advantage of the community. 



(a) THE NATURE-STUDY APPROACH. 



1. Properties of xvater. — (a) The boiling point and vapori- 

 zation of water can advantageously be studied by putting a pint 

 of water into an empty can. such, for instance, as has had linseed 

 oil or liquid paint in it. A larger can would serve even better. 

 By suitable means bring this water to the boiling point, and with 

 a thermometer (a cream thermometer is convenient) determine 

 the temperature of the vapor and of the boiling water by lower- 

 ing the thermometer into the can. That the can is now practically 

 filled with water vapor will come out impressively by taking the 

 can from the heating flame, stoppering tightly the mouth, and 

 then pouring cold water over the outside of the can so as to cool 

 the vapor within. Ordinarily, the can will weirdly collapse with 

 startling contortions, due to the removal of pressure from the 

 inside to counteract that of the air without. 



(1)) The freezing point of water may be determined by tak- 

 ing the temperature of water that has plenty of ice floating in it, 

 or by the employment of simple freezing mixtures in the pro- 

 duction of ice, for which see any good text-book on Physics. 



(c) The solvent power of water can easily be shown by 

 taking say two glasses of clear water from any ordinary source. 

 Into one put a teaspoon ful of salt and into the other a tea- 

 spoonful of sugar. Stir till both are as clear as before. If it is 

 felt to Ije worth while and "straws" enough can be inexpensively 

 secured, such as are used at the soda fountains, the pupils by 

 tasting luay verify the fact that the waters are now difl^erent 

 from what they were before, though they look the same. 



(d) The power of water to absorb gases, such as oxygen, 

 comes out by taking two small bottles of water that has had a 

 chance to take up the oxygen of the air, l)oiling one for several 



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