WHAT is used instead of soap because it will not create an insoluble s c u m when mixed with hard water.

Hard water contains salts of calcium and magnesium principally as bicarbonates, chlorides, and sulfates. Ferrous ion may also be present;

Explanation:

Hard water contains salts of calcium and magnesium principally as bicarbonates, chlorides, and sulfates. Ferrous ion may also be present; oxidized to the ferric form. It appears as a reddish brown stain on washed fabrics and enameled surfaces. Water hardness that is caused by calcium bicarbonates is known as temporary, because boiling converts the bicarbonates to the insoluble carbonates; hardness from other salts is called permanent. Calcium and magnesium ions in hard water react with the higher fatty acids off soap to form an insoluble gelatinous curd, thereby causing a waste of the soap.    

The  grandmother cell  is a hypothetical  neuronthat represents a complex but specific concept or object.[1]  it activates when a person "sees, hears, or otherwise sensibly discriminates"[2]  a specific entity, such as his or her grandmother. the term was in use at least as early as 1966 amongst staff and students in the department of experimental psychology, university of cambridge, england. a similar concept, that of the  gnostic neuron, was proposed two years later

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