GB744499A - Improvements in or relating to potassium nitrate and compositions containing it - Google Patents

Abstract

Alkali metal salts of disulphonic acids of dinaphthylmethane are prepared by heating under reflux a mixture of naphthalene sulphonic acid and formaldehyde in the presence of sulphuric acid and water and neutralizing the resulting liquor with an alkali metal hydroxide solution. Dependent upon the naphthalene sulphonic acid employed, salts of a : a 1-disulphonic acid of dinaphthylmethane or b : b 1 or a : b -disulphonic acid of dinaphthylmethane may be obtained. The salts are employed as crystal modifiers for potassium nitrate (see Group III). Specification 656,048, [Group III], is referred to.ALSO:Potassium nitrate having a reduced caking tendency consists of crystals thereof bearing a surface deposit of a salt soluble in a saturated aqueous potassium nitrate solution at 20 DEG C. of at least one compound definable as the condensation product of 1 mol of formaldehyde and 2 mols of a naphthalene monosulphonic acid, i.e. a salt, preferably sodium, of disulphonic acids of dinaphthyl methane. The sodium or other soluble salts of a :a 1, b :b 1 or a :b disulphonic acids or dinaphthyl methane may be employed, depending on the naphthalene sulphonic acid which is condensed with the formaldehyde, and the amounts employed should be at least 0.025 per cent and preferably 0.05 to 0.1 per cent of the dry weight of the nitrate. The surface deposition may be effected by dissolving a soluble salt of the dinaphthyl methane disulphonic acid in the aqueous solution from which the potassium nitrate is to be crystallized or the salt may be dissolved in water and sprayed or otherwise distributed over previously formed potassium nitrate crystals, after which the water is evaporated whilst agitating. Examples relate to the incorporation of 0.1 per cent of the sodium salt of b :b 1 and a :b disulphodinaphthylmethane in an aqueous nitrate solution from which the nitrate is crystallized with agitation, and to the use of 0.5 per cent of the sodium salt of b :b 1 and a :a 1 disulphodinaphthylmethane applied as a 10 per cent aqueous solution spray to potassium nitrate crystals. The effect of the addition of the above salts is comparable with that of the dyestuffs of sulphonated aromatic character disclosed in Specification 656,048, which is referred to, in that the strength of the bridges of recrystallized material which form between adjacent particles of potassium nitrate is reduced.