Caliche

Iodine occurs to a minute extent (less than 0.001 %) in sea water, but is found in greater concentration, combined in organic form, in certain seaweeds, in oysters and in cod livers. Crude Chile saltpetre, or caliche contains small amounts of sodium iodate, NalOj. from which iodine can be obtained (see below). Some insoluble iodides, for example liiose of silver and mercury(II), occur in Mexico. Iodine is found in the human body in the compound thyroxin in the thyroid gland deficiency of iodine in diet causes enlargement of this gland (goitre). 

Gr. iodes, violet) Discovered by Courtois in 1811, Iodine, a halogen, occurs sparingly in the form of iodides in sea water from which it is assimilated by seaweeds, in Chilean saltpeter and nitrate-bearing earth, known as caliche in brines from old sea deposits, and in brackish waters from oil and salt wells. 

Recovery of iodine from Chilean saltpetre differs entirely from its recovery from brine since it is present as iodate. NalOs is extracted from the caliche and is allowed to accumulate in the mother liquors from the crystallization of NaNOs... 

Sodium Nitrate (Chile Saltpeter, Cubic or Soda Niter, Caliche, Nitratine). NaN03, mw 85.01,... 

Na nitrate occurs native in large deposits in the rainless districts of Chile, hence it is often called Chile saltpeter or Chile niter . The Na nitrate in the deposits constitutes from 20 to 50% in a distinct stratum of earth known as caliche . The caliche is crushed and lixiviated in large tanks of w heated by steam. The settled soln is run off to crystallizers, where crude nitrate separates, the mother liquors being run back to the lixiviators. The crysts are washed with a little w and dried in the sun they contain 95—96% Na nitrate (Ref 1)... 

Guggenheim A process for extracting sodium nitrate from caliche, a native sodium nitrate found in Chile. The ore is leached at 40°C with water containing controlled concentrations of magnesium and calcium sulfates. Operated on a large scale in Chile. See also Shanks. 

Shanks An obsolete process for extracting sodium nitrate from caliche, a Chilean mineral. The ore was leached with sodium chloride solution at 70°C and the sodium chloride and nitrate were separated by fractional crystallization. See also Guggenheim. 

Urbansky ET, Brown SK, Magnuson ML, Kelty SK (2001) Perchlorate levels in samples of sodium nitrate fertilizer derived from Chilean caliche. Environ Pollut 112 299-302... 

The region is substantially covered by regolith sediments, which conceal prospective bedrock sequences. The regolith sediments include windblown sand, alluvial gravels, and caliche horizons. Commonly, the vertical profile of the regolith sediments consists of surface lag or loosely windblown sand underlain by weakly cemented sands and dense caliche-cemented sediments with gypsum. 

Guggenheim Process. A process for the manuf of Na nitrate from Chilean nitrate ore, caliche, in which heat is efficiently utilized and handling costs are kept to a minimum... 

The details of the soil profile studied by Vanden Heuvel (1966) show how the magnesio-silicates are associated with the caliche layer, that occurs in the soil profile itself (in the instance studied it covers the upper horizons). Table 3 shows the clay mineral assemblages identified. 

Formerly all the iodine was made from the ash of seaweed, and potash was a remunerative appendix to the iodine industry but just as the Stassfurt salts killed those industries which extracted potash from other sources, so did the separation of iodine from the caliche mother-liquors threaten the industrial extraction of iodine from seaweed with extinction. Iodine in a very crude form was exported from Chili in 1874—e.g. a sample was reported with iodine 52-5 per cent. iodine chloride, 3-3 sodium iodate, 13 potassium and sodium nitrate and sulphate, 15 9 magnesium chloride, 0 4 insoluble matter, 1 5 water, 25-2 per cent. About that time much of the iodine was imported as cuprous iodide. This rendered necessary the purification of the Chilian product but now the iodine is purified in Chili before it is exported. The capacity of the Chilian nitre works for the extraction of iodine is greater than the world s demand. It is said that the existing Chilian factories could produce about 5100 tons of iodine per annum whereas the... 

The extraction of iodine from caliche.—The mother-liquor—aqua vieja—... 

Costra is a kind of low-grade nitre rock or caliche running 5 to 17 per cent, sodium nitrate which does not pay to work the caliche runs 18 to 25 per cent., and in exceptional cases 50 to 60 per cent, sodium nitrate—the average runs 20 to 30 per cent. The deposits are close to the surface, and naturally vary a little in composition in different places. R. F. Blake and V. I OliVier s, and L. Dieulafait s analyses 5 of costra and caliche show ... 

In addition, the caliche contains 0-04-1-06 per cent, of potassium iodate, and the costra 003 per cent. the caliche 0 02-l"32 of potassium chlorate. A. T. Machattie gives from"0-73 to 1 90 per cent, of sodium iodate in caliche, and R. F. Blake and... 

---