🌱 Calcium oxide (CaO) content of agricultural limes and calcium fertilizers — titration with disodium edetate at pH 12–13 with calcon indicator, PN-C-87007-06

Physicochemistry PN-C-87007-06

Overview

WHAT THE STANDARD COVERS. The scope from the PKN card of the 1993 edition, quoted in full: "A complexometric titration method is given for determining the calcium oxide content of calcium fertilizers. Calcium ions are titrated with a standard solution of disodium edetate at pH 12 - 13 in the presence of calcon as the indicator. The conditions of the determination and the way of calculating the results are specified" (our translation). The scope from the card of the amendment PN-C-87007-06:1993/Az1:1997, quoted in full: "A method for determining calcium oxide in calcium fertilizers is presented. The field of application of the method, the principle of the method, the reagents and solutions used, the procedure and calculation of the results and the permissible difference between determination results are given" (our translation). The amendment thus describes the method anew, but its card does not say which; AB 284, which cites the standard with the amendment, records "acid-base (alkalimetric) titration", the others — "titrimetric method". Whether the amendment replaced complexometric titration with another method — WE DO NOT KNOW.

STATUS (state of the cards on 29 September 2026). Card of PN-C-87007-06:1993 (Polish version): heading "Wycofana" (withdrawn), published 22-02-1993, "Date of withdrawal: 07-09-2015", 2 pages, PKN technical committee KT 156 (Fertilizers), ICS 65.080, "Supersedes: PN-C-87007-11:1974"; there is no "Superseded by" field. Card of the amendment PN-C-87007-06:1993/Az1:1997: published 24-12-1997, "Date of withdrawal: 07-09-2015", 2 pages, KT 156. The PKN search for "PN-C-87007" (29 September 2026) shows the whole series "Calcium fertilizers" (sheets 00–20 from 1952–2000) — sheets labelled "Wycofana"; a successor of sheet 06 WE HAVE NOT ESTABLISHED.

HOW MANY LABORATORIES AND IN WHAT FORM (copy of the accreditation scope database, data up to 17 September 2026, read on 28 September 2026). All records of sheet 06: 14 entries at 14 laboratories. With amendment Az1 (also written "A1") — 10 laboratories, without it — AB 759, AB 820, AB 921 and AB 1186; AB 779 and AB 789 record both forms. Forms of the number: "PN-C-87007-06:1993" — 7 laboratories (AB 277, AB 284, AB 312, AB 333, AB 820, AB 1172, AB 1186), "PN-93/C-87007/06" — AB 317, AB 759, AB 921, "PN-C-87007/06:1993" — AB 779, AB 823, "PN-93/C-87007-06" — AB 789, "PN-C-87007-6:1993" — AB 930. Exclusions and clauses: "excluding clause 6" (AB 333), "excluding clause 1.2.a" (AB 312), "excluding clause 1.2 b)" (AB 779), "p.3" (AB 1172). The "Laboratories" tab searches for records BEGINNING with "PN-C-87007-06" and will show 7 laboratories — checked with the tab query on the labcoda.pl production server on 29 September 2026: 7; under "PN-93/C-87007/06" — 3, under "PN-C-87007-6" — 1; AB 779, AB 789 and AB 823 remain outside all three. Current scopes on the PCA website (read on 29 September 2026, issues from 7 March 2025 to 5 August 2026): all entries stand in the valid issues, every pair of range numbers from the copy appears in the current document and no entry is suspended; the full records of the reference documents agree with the copy.

OBJECT, TECHNIQUE AND RANGES. "Agricultural limes" (also "and liming materials") — 10 laboratories, "Calcium fertilizers" (also with liming materials) — AB 284, AB 930 and AB 1172, "Agricultural lime (calcium fertilizer)" — AB 333. Technique: titrimetric method — 13 laboratories, "acid-base (alkalimetric) titration" — AB 284. CaO ranges in percent: lower limits from 0.5 (AB 312) and 0.50 (AB 921) through 1.00 (AB 277), 1.50 (AB 789), 2.0 (AB 820), 3.7 (AB 284) and 5.0 (AB 333) to 15.0 (AB 317, AB 779, AB 1186) and 20.0 (AB 759, AB 823, AB 930, AB 1172); upper limits from 65.0 (AB 921) and 70.0 (AB 317) through 80.0 (seven laboratories) and 90 (AB 333, AB 759, AB 820, AB 930) to 99.9 (AB 284).

ALONGSIDE THIS STANDARD. Magnesium-containing agricultural limes are tested by 11 of these 14 laboratories according to PN-C-87006-11:1990 — calcium oxide (usually "p. 4") and magnesium oxide ("p. 6"): AB 312, AB 317, AB 333, AB 759, AB 779, AB 789, AB 820, AB 921, AB 930 and AB 1186, while AB 277 cites both standards in the same entry. PN-C-87006-11:1990 is also cited by AB 798 — without PN-C-87007-06 (issue no. 21 of 6 March 2026). According to European standards, calcium in agricultural limes and liming materials is determined by: PN-EN 13475:2003 — AB 006, AB 180 and AB 339; PN-EN 12946:2023-11 — AB 006; the neutralizing value expressed as CaO — a different quantity — according to PN-EN 12945+A1:2016 by AB 006, AB 180, AB 333 and AB 339.

WHAT WE DO NOT GIVE. We did not have the text of the standard or of the amendment — PKN sells them (2 pages each). We do not give the sample mass, the way it is dissolved, the concentration of the edetate, the way the pH is set, the equation, the permissible difference between results or the content of clauses 1.2, 3 and 6, which laboratories exclude or indicate.

Method principle

According to the card of the 1993 edition, calcium ions from the solution of the calcium fertilizer sample are titrated with a standard solution of disodium edetate at pH 12–13 with calcon as the indicator, and the content is expressed as calcium oxide. Amendment Az1:1997 describes the method anew (field of application, principle, reagents, procedure, calculation, permissible difference of results), but its card does not say which method. We DO NOT GIVE the conditions of the determination — we did not have the text of the standard.

Applications

• Calcium oxide in agricultural limes, calcium fertilizers and liming materials — in the scopes of 14 laboratories
• Magnesium-containing limes — according to PN-C-87006-11:1990 (11 of these 14 laboratories; together with AB 798 — 12), not according to this standard

Key parameters

Standard

Standard number

PN-C-87007-06:1993 (wersja polska) ze zmianą PN-C-87007-06:1993/Az1:1997

Title (PL)

Nawozy sztuczne wapniowe — Oznaczanie zawartości tlenku wapniowego

Title (EN)

Calcium fertilizers — Determination of calcium oxide content

Step-by-step procedure

1. Status of the document

   PKN cards: the standard and amendment Az1:1997 withdrawn on 07-09-2015, no successor indicated (state of the cards on 29 September 2026).

2. Sample solution

   Preparing a solution from the calcium fertilizer sample; mass and way of dissolution NOT GIVEN.

3. Titration

   Calcium ions are titrated with a standard solution of disodium edetate at pH 12–13 with calcon (card of the 1993 edition).

4. Result

   Calcium oxide (CaO) content in percent; equation and permissible difference of results NOT GIVEN.

Reagents, media and consumables

Health and safety (OHS)

• Quicklime reacts with water, releasing heat, and is corrosive — eye and skin protection when preparing the sample; solutions at pH 12–13 are strongly alkaline
• NOTE ON SUBSTANCE: for magnesium-containing limes the scopes cite a different standard (PN-C-87006-11:1990) — when asking about a test, state the type of lime

Frequently asked questions