Patent GB-786738-A (GB)
Title: Improvements in or relating to silicic gels
IPC: C01B33/154
Filed: 1954-05-17
Abstract: A fertilizer or soil improver comprises an amorphous silicic gel obtained by precipitating an alkali metal silicate solution with formic or acetic acid or with a calcium or zinc salt thereof, in a proportion of 100 parts of such alkali metal silicate solution, as defined below, to 4 to 8 parts of the said precipitant and thereafter partially dehydrating the resulting gel at room temperature and finally drying the gel at 50-60 DEG  C.  The alkali metal silicate is a sodium or potassium water glass, the former having a density of 35 to 40 DEG  Be and containing 20-30 per cent SiO2 and the latter having a density of 28-30 DEG  Be and containing 20-30 per cent SiO2. The production of the gel may be effected in the presence of a carbonate of an alkali or alkaline earth metal or zinc or magnesium preferably in natural form as marls, clay marls, or loess.  In addition, a polymeric organic carboxylic acid such as polyacrylic acid may be added prior to precipitation.  According to examples: (1) potassium silicate solution was precipitated by formic acid and the resulting gel without filtering was dehydrated for 2-3 days at room temperature and thereafter dried at about 50 DEG C.  (3) Potash and soda water glass in the proportion of 3-2 were rendered alkaline by potassium hydroxide and a mixture of zinc carbonate and dolomite was added to the solution with stirring.  The solution was then precipitated by the addition of zinc acetate and the resulting gel was dehydrated and dried as in (1) above.  (4) The mixture of zinc and magnesium carbonates were moistened and stirred with potash water glass and the mixture precipitated with calcium formate dissolved in water.  (5) Individual suspensions were prepared from zinc carbonate, magnesium carbonate and calcium carbonate with water and after mixing the free suspensions were stirred together and added to potash water glass with stirring after which a solution containing zinc formate and zinc acetate was added to precipitate the mixed gel which was dehydrated in air and dried at 50 DEG  to 60 DEG  C.  (6) Zinc carbonate and magnesium carbonate were moistened and stirred with potash water glass containing a small amount of polyacrylic acid and the mixture was precipitated by calcium formate dissolved in water. (7) A mixture of potash and soda water glass were mixed with pulverized dolomite and zinc carbonate and after the addition of a small amount of polyacrylic acid the suspension was precipitated with aqueous calcium formate and the resulting gel dehydrated and dried as before.  Specification 730,464, [Group I], is referred to.ALSO:A fertilizer or soil improver comprises an amorphous silicic gel obtained by precipitating an alkali metal silicate solution with formic or acetic acid or with a calcium or zinc salt thereof, in a proportion of 100 parts of such alkali metal silicate solution, as defined below, to 4 to 8 parts of the said precipitant and thereafter partially dehydrating the resulting gel at room temperature and finally drying the gel at 50 DEG -60 DEG C.  The alkali metal silicate is a sodium or potassium water glass, the former having a density of 35 degrees to 40 degrees Be and containing 20-30 per cent SiO2 and the latter having a density of 28 degrees to 30 degrees Be and containing 20-30 per cent SiO2.  The production of the gel may be effected in the presence of a carbonate of an alkali or alkaline earth metal or zinc or magnesium preferably in natural form as marls, clay marls, or loess.  In addition a polymeric organic carboxylic acid such as polyacrylic acid may be added prior to precipitation. According to examples (1) potassium silicate solution was precipitated by formic acid and the resulting gel without filtering was dehydrated for 2-3 days at room temperature and thereafter dried at about 50 DEG C.  (3) Potash and soda water glass in the proportion of 3-2 were rendered alkaline by potassium hydroxide and a mixture of zinc carbonate and dolomite was added to the solution with stirring. The solution was then precipitated by the addition of zinc acetate and the resulting gel was dehydrated and dried as in (1) above.  (4) The mixture of zinc and magnesium carbonates were moistened and stirred with potash water glass and the mixture precipitated with calcium formate dissolved in water.  (5) Individual suspensions were prepared from zinc carbonate, magnesium carbonate and calcium carbonate with water and after mixing the free suspensions were stirred together and added to potash water glass with stirring after which a solution containing zinc formate and zinc acetate was added to precipitate p  the mixed gel which was dehydrated in air and dried at 50 DEG  to 60 DEG C.  (6) Zinc carbonate and magnesium carbonate were moistened and stirred with potash water glass containing a small amount of polyacrylic acid and the mixture was precipitated by calcium formate dissolved in water.  (7) A mixture of potash and soda water glass were mixed with pulverized dolomite and zinc carbonate and after the addition of a small amount of polyacrylic acid the suspension was precipitated with aqueous calcium formate and the resulting gel dehydrated and dried as before.  Specification 730,464 is referred to.