WASHING POWDERS 145 



that the housewife prefers rain water for laundry and general 

 work. Rain water, coming as it does from the clouds, is free 

 from the chemicals gathered by ground water, and is practically 

 pure. While foreign substances do not necessarily injure 

 water for drinking purposes, they often prevent soap from 

 forming an emulsion. Under such circumstances the water is 

 said to be hard, and soap used with it is wasted. Even if water 

 is only moderately hard much soap is wasted. The substances 

 which make water hard are calcium and magnesium salts. 

 When soap is put into water containing either or both of these, 

 it combines with the salts to form sticky insoluble scum. It 

 is therefore not free to form an emulsion and to remove grease, 

 and is valueless as a cleansing agent. 



A slight amount of hardness in water does not seriously affect 

 the cleansing value of soap for toilet purposes. But it does 

 seriously lessen the efficiency of soap in laundry work. In the 

 laundry much soap is needed, and even a slight loss in scum 

 would mean vast waste of soap and money in a short time. 

 The addition of washing soda, or sodium carbonate, to hard 

 water softens it and makes it suitable for laundry purposes. 

 Washing soda combines with calcium and magnesium and pre- 

 vents them from uniting with soap. The soap is thus free to 

 form an emulsion, just as in soft water. In some cities where 

 the water is very hard, as in Columbus, Ohio, it is softened 

 and filtered at public expense, before it leaves the reservoirs. 

 But even under these circumstances, a moderate use of wash- 

 ing powder is general in laundry work. 



Washing powder is often strongly alkaline. If it is put on 

 clothes dry, or is thrown into a crowded tub, it will eat the 

 clothes. The only safe method is to dissolve the powder before 

 the clothes are put into the tub. The trouble with many 

 laundries is that they are careless about this and do not dissolve 

 the powder before mixing it with the clothes. 



