THE EXTRACTION OF POTASH FROM FELDSPATHIC ROCK.¹

Abstract

The extraction of potash from native rocks has long been considered one of the most important as well as one of. the most difficult problems of industrial chemistry. In spite of the enormous resources of the .North American continent, there has not yet been found anywhere on it an available source of potash, thus necessitating the importation from abroad of many hundreds of millions of pounds per annum of the salts and compounds of this important substance. One result of this lack of a native source of supply has been to stimulate the use in agriculture of hard wood ashes, which are even at the present time brought from Canada in considerable quantities to the added devastation of the fast disappearing forests. In addition to this, cotton hull ashes from the South are shipped to the North, which merely robs the soil of one portion of the country to supply the deficit in another. The pegmatitic granites and feldspathic dykes of the eastern and central western United States offer an unlimited source of supply which only awaits an economical method for making it available. Many of these feldspar deposits run as high as 10 per cent, in potash (K20) and it follows, therefore, that a quarry only fifty feet square and fifty in depth contains about 2,000,000 pounds of this alkali.Under the stimulus of the rapidly growing cement industry, great advance has been made in the last few years in the art and economics of fine grinding, which must of necessity be the first step in any process which attempts the extraction of potash from feldspar or other minerals. At the present time, in the manufacture of Portland cements, at least two extremely fine grindings as well as a burning at a high temperature are accomplished so economically that the finished product can be packed in bags or barrels and sold in some places for a price equal to about threetenths of a cent per pound or about six dollars per ton. In view of the fact that a short ton of 10 per cent, feldspar contains about ten dollars' worth of potash at prevailing prices the problem of extraction is not on first thought an unpromising one from an economical standpoint.There are about twenty well defined rock-forming minerals as com-1 Paper read before the N. Y. Section, Am. Chem. Soc., Feb. 7, 1907. Published with the permission of the Secretary of Agriculture.Potash-bearing Silicates Arranged According to Dana. ORTHOSILICATES.Kaliophilite: Silicate of alumina and potash. K20, 27,20-29.30 per cent.Microsommite: Sulpho-silicate of alumina, lime, soda, and potash. K20,6.25-7.82 per cent.Nephelite: Silicate of alumina, soda, and potash. K20, 4.55-7.14 per cent.Hauynite: Sulpho-silicate of alumina, lime, and soda (potash). K20, 0.33-4.96 per cent.Algerite: Silicate of alumina, magnesia, and potash, and water with some CaC03. K20, 9.97 per cent. metasilicates.Leuciie: Silicate of alumina and potash. K20, 18.90-21.48 per cent. POLYSILICATES.Orthoclase: Silicate of alumina and potash. K20, 5.40-15.99 per cent. Constitutes at least 15 per cent, of the earth's crust and occurs in...

Historical and technical developments of potassium resources

“…The former mainly centered on the use of hydrofluoric acid (HF). The latter centered on attempts to liberate potassium via formation of amorphous and/or new solid-state phases (Cushman and Coggeshall, 1912;Cushman and Hubbard, 1908;Ross, 1913;Ross, 1917;Spiller, 1882). This second approach was probably the logical consequence of applying treatments similar to the analytical method of Lawrence Smith (Hart, 1915;Smith, 1871).…”

Potassium recovery from Brazilian glauconitic siltstone by hydrothermal treatments

“…Publications dealing with the acidic dissolution of silicate rocks date back to the early 20th century (Cushman and Hubbard, 1908). Varadachari (1992) showed that potassium can be recovered from biotite through concentrated acidic solutions.…”