Water 63 



f 



in water, but how readily the grease comes out of the cloth if you 

 first rub it with soap and then rinse it in water. Soap is necessary 

 to cleanliness. It is made of fat and of a product called lye ob- 

 tained by treating wood ashes with water and lime. 



The preparation of soap may be shown in the following 

 manner: Fill a beaker one-third full of water and one-third 

 full of a mixture of lard and lye, in the proportion of three 

 parts of lard to one part of lye. Caution: Do not allow the 

 lye to touch the hands or clothes. Boil the mixture for 45 min- 

 utes; then pour it into a pan and let it cool and set for several 

 hours. 



Formerly it was customary to use the hands in washing soiled 

 clothing. It required hard rubbing to make the soap and water 

 combine with the greasy dirt in the clothes. Now laundry machin- 

 ery is used to do this work. The clothes are placed in a box-like 

 enclosure having an apparatus capable of whirling them in a soap 

 and water solution. This apparatus is run by the use of elec- 

 tricity or steam, thus relieving the housekeeper of much hard 

 work. 



Alkalis and Acids. An alkali is one of a class of substances 

 widely used in cleansing, and in counteracting the effect of acid. 

 Alkalis are soluble in water or alcohol and, when combined with 

 fats or oils, make soap. Baking soda, caustic potash or lye, and 

 household ammonia are common alkalis. The presence of an 

 alkali may be shown by the use of litmus paper. An alkali turns 

 red litmus paper blue. 



Acids may be recognized by their sour taste, and by the fact 

 that they turn blue litmus paper red. Unless immediately counter- 

 acted by an alkali, most acids will eat holes in materials upon 

 which they are spilled. 



When an acid and an alkali are combined in proper proportion 

 a salt is formed. This process is called neutralization. While 

 strong acids and alkalis may injure objects with which they come 

 in contact, salts are harmless. For example, when sulphuric acid 

 from a radio battery has been spilled on clothes, the immediate 

 application of an alkali such as household ammonia will form a 

 harmless salt and save the clothes. 



