If you travel round the world, you will notice that tap water varies from place to place. In some places (Europe), tap water is generally hard (i.e. #pH# #>=# #7.3#); this makes it hard to build a lather from soap. In other places, and I think specifically of the Pacific Northwest, Washington, and British Columbia, water is soft, #pH# #<=# #7.0#; soap is very easy to lather and the water tastes good. So-called water-hardness describes water that is slightly alkaline. Of course, the #pH# scale is logarithmic, and even slight changes in #pH# represents large changes in acid (#H_3O^+#) concentration.
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