WATER 9 



It has been frequently stated that very hard water is the cause 

 of indigestion and malnutrition with both animals and people, and 

 it is said that horses compelled to drink hard water develop a dry, 

 hard coat and become dyspeptic. It has even been suggested that 

 the perpetual drinking of such a water results in the formation of 

 intestinal calculi, a supposition that is devoid of proof. Very soft 

 water, being deficient in lime, has been considered to be one of the 

 causal factors of rickets, but the lime available in moderately hard 

 water is scarcely worth consideration compared with the demands 

 of a growing child or animal. It is now known that rickets and 

 soft teeth are more closely associated with vitamine-deficient foods 

 than with supposed calcium deficiency. For all general uses a 

 moderately hard water, one containing about 12 parts of calcium 

 carbonate per 100,000, is to be preferred to one either very soft 

 or very hard. For making sheep-dips, solutions of disinfectants 

 and for similar purposes a soft water should be chosen. 



Softening Hard Water. As hard water is undesirable for 

 domestic and most manufacturing purposes, measures are taken 

 to reduce the hardness before it is delivered to the consumer. The 

 temporary hardness due to calcium and magnesium carbonates can 

 be removed by boiling when only small quantities have to be dealt 

 with, but this leaves the water deficient in dissolved gases and there- 

 fore insipid and unpleasant to drink. When large quantities have 

 to be softened, as for instance the main water supply of a township, 

 such a method as boiling is impracticable. 



As the calcium and magnesium carbonates are held in solution 

 as bicarbonates by the CO 2 in the water, they become precipitated 

 as the carbonates on the addition to the water of any substance that 

 will unite with the CO 2 . This is what occurs when slaked lime 

 is mixed with the water. This method was brought out by Dr. 

 Clark, and is known as Clark's Method of Water Softening. The 

 changes that take place are as here shown : 



MgH 2 (C0 3 ) 2 +Ca(HO) 2 = 



1 oz. of lime is added to every 100 gallons for each grain of calcium 

 per gallon. 



The calcium carbonate is more readily thrown out of solution 

 than is the magnesium carbonate, and Clark's process is therefore 

 especially adapted for the treatment of water having a chalk origin. 

 The slaked lime does not remove all the calcium carbonate, and it 

 is found that about two grains per gallon remain in solution. In 

 order to get rid of the magnesium carbonate excess of lime has to 



