Softening Water by Filtering It 



For domestic use a water softener is 

 an absolute necessity to prevent waste 



THE production oi absolutely soft 

 water (water of zero hardness) is 

 one of the most notable recent 

 achievements of industrial chemistry. A 

 little more than half a century ago two 

 English chemists, Clark 

 and Porter, discovered 

 that the addition of lime 

 and carbonate of soda 

 would reduce the hard- 

 ness of natural waters. 

 To soften water com- 

 pletely, however, was 

 considered an impossi- 

 bility, save by distilla- 

 tion. Then came Dr. 

 Robert Gans, a chemist 

 in the service of the 

 German Geological Sur- 

 vey, with the discovery 

 that certain substances 

 in the soil, known as 

 zeolites, had the power 

 of absorbing hardness 

 from water brought in 

 contact with them. 

 Since the capacity of 

 natural zeolites to effect 

 this change was found to 

 be too weak for commer- 

 cial use. Dr. Gans set 

 about the production of 

 an artificial zeolite which 

 he called Permutit. 

 His artificial product 

 softens the hardest of 

 natural waters. Fur- 

 thermore it is entirely in- 

 soluble and can be used 

 over and over again. 



Permutit is essentially 

 a silicate of sodium and 

 aluminum and when 

 hard water, that is, 

 water containing in solu- 

 tion salts of calcium and magnesium, is 

 passed through a filtering medium of this 

 substance, the sodium in the permutit 

 changes place with the calcium and 

 magnesium, which remain in the filter, 

 thus substituting sodium salts for them 



Water 

 inlet 



Soft 



water 



outlets 



f 



and softening the hardest natural water. 

 Permutit is of a granular and flaky tex- 

 ture, very porous, exceedingly tough and 

 possessing a mother-of-pearl lustre. It is 

 made by fusing in definite proportions the 

 minerals, feldspar, 

 kaolin, pearlash and 

 soda. The fused 

 mass is crushed. 

 After the soluble 

 matter is washed out 

 the mass is ready 

 for use. 



Permutit can be 

 regenerated when all 

 of its sodium has 

 been exchanged for 

 calcium magnesium. 

 This is accomplished 

 by allowing a solu- 

 tion of ordinary 

 table salt to stand 

 the filter over 



Crushed marble 

 suppqrted on : 

 screen 



^^Permutit 

 *^ ,on gravel 



^Collection 

 ^chamber 



let to sewerfor back 

 sh cleansing water -' 



Above: How the water is 

 softened simply by pass- 

 ing it through a filter 

 filled with permutit 



At right: A filter which 

 supplies thousands of gal- 

 lons of soft water a day 

 for industrial purposes 



night. The calcium and magnesium in 

 the filter are replaced automatically with 

 sodium, and the filter, after a washing of 

 about thirty minutes, is again ready for 

 use. There are filters which have been 

 regenerated nearly three thousand times. 



S-'iO 



