the change that causes the manufacture of salt from seawater is evaporation.
the change that causes the manufacture of salt from seawater is evaporation.
manufacture of salt from seawater is which change?
evaporation
the manufacture of salt is one of the oldest chemical industries. a major source of salt is seawater, which has a salinity of approximately 3.5%. this means that there are about of dissolved salts, predominantly sodium () and chloride () ions, per kilogram (2.2 lbs) of water. the world's oceans are a virtually inexhaustible source of salt, and this abundance of supply means that reserves have not been calculated. the evaporation of seawater is the production method of choice in marine countries with high evaporation and low precipitation rates. salt evaporation ponds are filled from the ocean and salt crystals can be harvested as the water dries up. sometimes these ponds have vivid colours, as some species of algae and other micro-organisms thrive in conditions of high salinity.
salt
salt production during china’s ming period mainly took place in china’s coastal regions and salt lakes . although there were different techniques to obtain salt, boiling seawater and evaporating seawater under the sun were the two popular methods of isolating salt. both techniques of salt production required dry and sunny weather. during ming times, boiling seawater was the most prevailing technique. salt producers laid down reeds and straws to absorb and concentrate seawater and then boiled to isolate the salt grains. the technique was of sunshine exposure occasionally used in fujian and was not commonly applied nationally until the late ming period. saltern households were generally called "yan hu"(盐户), and specifically, those who boiled seawater were called "zao hu"(灶户). other techniques were applied in inland regions of china. in yunnan, salt was obtained through the mining of saline rocks. in shanxi and shaanxi, salt was gathered in the summer when the salt lake dried up. and in sichuan, brine wells were dug and then the brine was boiled. household that boiled brine also had to obtain fuel, in the form of natural gas or burning firewood and straw, in order to heat up their furnaces.
salt in chinese history