XIII. 



THE RELATIVE ADVANTAGES OF HARD AND SOFT WATER, 

 WITH SPECIAL REFERENCE TO THE SUPPLY OF WATFORD. 



By John Hopkinson, F.L.S., F.G.S., F.R.Met.Soc. 



Bead at Watford, 29<A January, 1895. 



The question of the relative advantages of hard and soft water 

 is a very wide one. Considered in an economic light it cannot be 

 denied that the advantages are decidedly in favour of soft water ; 

 considered from a sanitary point of view it must first be resolved 

 into two distinct questions, — the one as to the external application 

 of water (for ablution) ; the other as to its internal use (for 

 imbibition). That soft water has great sanitary advantages over 

 hard water in our ablutions is no more likely to be disputed than 

 that it is decidedly more economical in domestic use, — for washing 

 ourselves as well as for washing our clothes and cooking our food, 

 — and the only sanitary question which is really open to debate is 

 whether soft water or hard water is best for us to drink. But this 

 should not be the only point discussed, for the amount of water 

 which we drink is but a very small portion of that which we use 

 in other ways. It is therefore to the purpose to show that if hard 

 water and soft water were equally beneficial in this respect, the 

 advantages on the whole would be greatly in favour of soft water ; 

 and of this I think there cannot be the slightest doubt. 



The hardness of water may be expressed in two different ways, 

 in parts per 100,000 by weight, and in grains per gallon. In 

 general analyses of water the former scale is usually adopted, for 

 the sake of uniformity, the amount of organic and mineral in- 

 gredients in water being most clearly and advantageously expressed 

 on this scale ; but the latter, which is known as Clark's scale, is 

 more familiar to us, and I will here adopt it. A grain of carbonate 

 of lime being the 1-70, 000 th part by weight of a gallon of water, 

 parts per 100,000 can be converted into grains per gallon by 

 multiplying by seven and dividing by ten, and vice versa. 



The water with which Watford is supplied derives its hardness 

 mainly from the presence of bicarbonate of lime ; not from that of 

 sulphates or chlorides which are much more difficult to deal with. 

 It is usually about 20 degrees of hardness, about 16° of which 

 are temporary, that is can be removed by boiling, and 4° are 

 permanent, that is cannot be so removed. The mean of two 

 analyses of water from the well at the Watford Waterworks made 

 in 1870 and 1873 for the Rivers Pollution Commission, gave 20°-0, 

 16°-3 being temporary and 3°'7 being permanent. Several other 

 analyses of water from wells in the neighbourhood of Watford, 

 made about the same time (1870 to 1873), gave from 18° 

 to 22° ; and the mean of 16 analyses of water from wells and 

 springs in Hertfordshire, made from 1868 to 1874, gave a total 



