On food and cooking the science and lore of the kitchen ( PDFDrive ) 1213

revolutionaryFrancetoGandhi’s1930salt
marchtoDandi.
SaltProduction

Peoplehavebeengatheringcrystallinesalt
sinceprehistorictimes,bothfromthe
seacoastsandfrominlandsaltdeposits.The
rock-saltdeposits,someofwhichare
hundredsofmillionsofyearsold,aremasses
ofsodiumchloridethatcrystallizedwhen
ancientseaswereisolatedbyrisingland
massesandevaporated,andtheirbedsthen
coveredoverbylatergeologicalprocesses.
Untilthe19thcentury,saltwasproduced
mainlyforthepreservationandflavoringof
foods.Nowadayslargeamountsareusedin
industrialmanufacturingofallkinds,aswell
asinthede-icingofwinterroads,andsalt
productionitselfhasbeenindustrialized.Most
rocksaltisnowminedbysolution,or
pumpingwaterintothedepositstodissolve


thesalt,thenevaporatingthebrinedownin
vacuumchamberstoformsolidcrystals.
Whilesomeseasaltisstillproducedby
gradualsolarevaporationfromopen-airsalt
pansinsufficientlywarm,dryregions,much
isnowproducedbymorerapidvacuum
evaporation.
Removing Bitter Minerals Salt comes from

seawater, and seawater contains significant
quantities of several bitter minerals, the
chloride and sulfate salts of magnesium and
calcium. Producers have a couple of ways of
dealingwiththeseminerals.Theycanremove
them from rock salt by dissolving the salt,
then adding sodium hydroxide and carbon
dioxidetothebrinetoprecipitatemagnesium
and calcium. They can remove them from
seawater by the same means, or else by slow
and gradual concentration in open-air pans,
during which the calcium salts become
insoluble, crystallize, and settle before the