{
  "url": "https://openlegislation.uk/fertilisers-sampling-and-analysis-regulations-northern-ireland-1996/schedule-2/part-I/chapter-4b./paragraph-4",
  "json_url": "https://openlegislation.uk/fertilisers-sampling-and-analysis-regulations-northern-ireland-1996/schedule-2/part-I/chapter-4b./paragraph-4.json",
  "legislation": "nisr/1996/513",
  "legislation_title": "Fertilisers (Sampling and Analysis) Regulations (Northern Ireland) 1996",
  "legislation_url": "https://openlegislation.uk/fertilisers-sampling-and-analysis-regulations-northern-ireland-1996",
  "path": "schedule/2/part/I/chapter/4b./paragraph/4",
  "kind": "paragraph",
  "number": "4",
  "heading": "REAGENTS",
  "text": "4.1 Sulfuric acid (ρ = 1.84 g/ml).\n4.2 Powdered iron reduced in hydrogen.\n4.3 Potassium sulfate, finely pulverised.\n4.4 Sulfuric acid, 0.05 M solution. } for variant (a) (see page 21)\n4.5 Sodium or potassium hydroxide, 0.1 M solution, carbonate free. } for variant (a) (see page 21)\n4.6 Sulfuric acid, 0.1 M solution. for variant (b) } for variant (b) (see page 21)\n4.7 Sodium or potassium hydroxide, 0.2 M solution, carbonate free. } for variant (b) (see page 21)\n4.8 Sulfuric acid, 0.25 M solution. } for variant (c) (see page 21)\n4.9 Sodium or potassium hydroxide, 0.5 M solution, carbonate free. } for variant (c) (see page 21)\n4.10 Indicator solutions:\nMixed indicator:\n4.10.1 Solution A: dissolve 1 g methyl red in 37 ml 0.1 M sodium hydroxide solution and make up to 1 litre with water.\nSolution B: dissolve 1 g methylene blue in water and make up to 1 litre. Mix 1 volume of A with 2 volumes of B.\nThis indicator is violet in acid solution, grey in neutral solution and green in alkaline solution. Use 0.5 ml (10 drops) of this indicator solution.\nMethyl red indicator:\n4.10.2 Dissolve 0.1 g methyl red in 50 ml 95% ethanol, make up to 100 ml with water and filter if necessary. This indicator (4 to 5 drops) may be used instead of the preceding one.\nSolution of stannous chloride:\n4.11 Dissolve 120 g of stannous chloride (SnCl2.2H2.O) in 400 ml concentrated hydrochloric acid (ρ = 1.18 g/ml) and make up to 1 litre with water. The solution must be completely clear and prepared immediately before use.\nIt is essential to check the reducing power of the stannous chloride. Dissolve 0.5 g of stannous chloride in 2 ml concentrated hydrochloric acid (ρ = 1.18 g/ml) and make up to 50 ml with water. Then add 5 g of Rochelle salt (potassium sodium tartrate) and a sufficient quantity of sodium bicarbonate for the solution to show an alkaline reaction to a litmus paper test.\nTitrate with 0.1 M iodine solution in the presence of a starch solution as an indicator.\n1 ml of 0.1 M iodine solution corresponds to 0.01128 g SnCl2.2H2O.\nAt least 80% of the total tin present in the solution thus prepared must be in the bivalent form. For the titration at least 35 ml of 0.1 M iodine solution should be used.\n4.12. Sodium hydroxide solution, 30 g per 100 ml, ammonia free.\n4.13 Standard nitrate-ammoniacal solution:\nWeigh out 2.500 g of potassium nitrate and 10.160 g of ammonium sulfate into a 250 ml graduated flask. Dissolve in water and make up to 250 ml. 1 ml of this solution contains 0.010 g of nitrogen.\n4.14 Anti-bump granules of pumice stone, washed in hydrochloric acid and ignited.",
  "extent": null,
  "status": null,
  "version": "current",
  "annotations": [],
  "outstanding_effects": [],
  "provenance": {
    "source": "legislation.gov.uk",
    "source_url": "https://www.legislation.gov.uk/nisr/1996/513/schedule/2/part/I/chapter/4b./paragraph/4",
    "retrieved_at": "2026-10-29T02:32:40.012993+00:00"
  },
  "licence": "Open Government Licence v3.0",
  "licence_url": "https://www.nationalarchives.gov.uk/doc/open-government-licence/version/3/",
  "attribution": "Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives."
}