「Rocky minerals with dog erection and array of orifices」: SALTS were used to cleanse, dry, and disinfect the flesh seam created by bending over the sole of each foot into a hairpin shape, and it requires little if any imagination to understand how this condition also applies to all the given meanings. Concubines and service providers used salts in the deep skin slits of their bound feet, a likely source of the English expression meaning to accept the bad along with the good but have some skepticism and reservations,「take it with a grain of salt.」Even only one single grain of salt remaining in the flesh seam of a no-longer-integrated foot would cause discomfort to a client, but hey, that was just par for the course which was ordered and paid for.
A chemical base that neutralizes (「harmonizes with」) an acid normally forms a salt. Concubines used salts in the deep skin slits of their bound feet to accomplish two things at once: dry the skin, and disinfect any wounds or straggling bacteria left by clients. If used for long periods or in high concentrations, alkaline compounds will literally dissolve human skin, smoothing the surface and leaving all the providers with「the same feeling among all.」Alkaline compounds when blended with lipids (fat) and heated, form what are called「soaps.」
Feces is generally quite salty due to the strong acids present in CHYME released in the stomach being neutralized by the strong bases released by the pancreas, liver bile and other glands into the small intestine:
「After hours of mechanical and chemical digestion, food has been reduced into chyme. As particles of food become small enough, they are passed at regular intervals into the small intestine, which stimulates the pancreas to release fluid containing a high concentration of bicarbonate. This fluid neutralizes the gastric juice, which can damage the lining of the intestine, resulting in duodenal ulcer. Other secretions from the pancreas, gallbladder, liver, and glands in the intestinal wall help in digestion. When food particles are sufficiently reduced in size and composition, they are absorbed by the intestinal wall and transported to the bloodstream. Some food material is passed from the small intestine to the large intestine. In the large intestine, bacteria break down proteins and starches in chyme that were not fully digested. When all of the nutrients have been absorbed from chyme, the remaining waste material changes into semi solids called feces, which then passes to the rectum, to be stored until it is ready to be expelled from the body.」
[ https://en.wikipedia.org/wiki/Chyme 2014-11-11 ]

External source definitions …excluding politically incorrect concepts and other meanings deemed offensive today; may include extended definitions, euphemisms, and mnemonics)
Chinese: base; alkali; soda (chemistry)
Japanese EDRDG: alkaline, alkali, lye, salt
Unihan extended: alkaline, alkali, lye, salt