AFRICAN 
STANDARD  DARS  
1488 
First Edition 2018  
 
 Reference No. ARS 1488:2018 (E) 
ICS 65.080  
 
 
© ARSO  2018  
  
 
 
 
 
 
 
 
 
 
Potassium sulphate (sulphate of potash) fertilizer — Specification  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 DARS  1488:2018  
ii © ARSO 2018 — All rights reserved   
Table of contents  
 
1 Scope  ................................ ................................ ................................ ................................ .............  1 
2 Normative references  ................................ ................................ ................................ .....................  1 
3 Terms and definitions  ................................ ................................ ................................ .....................  1 
4 Requirements  ................................ ................................ ................................ ................................ . 2 
4.1 General description  ................................ ................................ ................................ ................  2 
4.2 Physical requirements  ................................ ................................ ................................ ...........  2 
4.3 Chemical requirements  ................................ ................................ ................................ ..........  2 
4.4 Heavy metal contaminants  ................................ ................................ ................................ .... 2 
5 Sampling  ................................ ................................ ................................ ................................ .........  2 
6 Tests  ................................ ................................ ................................ ................................ ...............  2 
6.1 Methods of test  ................................ ................................ ................................ ......................  2 
6.2 Inspection ................................ ................................ ................................ ...............................  3 
7 Compliance  ................................ ................................ ................................ ................................ ..... 3 
8 Packaging and labelling  ................................ ................................ ................................ .................  3 
8.1 Packaging  ................................ ................................ ................................ ..............................  3 
8.2 Labelling ................................ ................................ ................................ ................................ . 3 
9 Certificate of analysis  ................................ ................................ ................................ .....................  3 
10 Material safety  ................................ ................................ ................................ ................................  3 
 DARS 14 88:2018  
© ARSO 2018 — All rights reserved  iii  
Foreword  
 
The African Organization for Standardization (ARS O) is an African intergovernmental organization 
established by the United Nations Economic Commission for Africa (UNECA) and the Organization of 
African Unity (AU)  in 1977 . One of the fundamental mandates of ARSO is to develop and harmoniz e 
African Standards (ARS) for the purpose of enhancing Africa’s i nternal trading capacity, increase 
Africa’s product and service competitiveness globally and uplift the welfare of African communities.  
The work of preparing African  Standards is normally carried out through ARSO  technical committees. 
Each Member State  interested in a subject for which a technical committee has been established has 
the right to be represented on that committee. International organizations, Regional Economic 
Communities (RECs), governmental and non -governmental  organizations , in liaison with  ARSO , also 
take part in the work.  
 
ARSO  Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.  
 
The main task of technical committees is to prepare ARSO  Standards. Draft ARSO  Standards 
adopted by the technical commit tees are circulated to the member bodies for voting. Publication as an 
ARSO  Standard requires approval by at least 75 % of the member bodies casting a vote.  
 
Attention is drawn to the possibility that some of the elements of this document may be the subjec t of 
patent rights. ARSO  shall not be held responsible for identifying any or all such patent rights.  
 
This African Standard was prepared by the ARSO Technical Harmonization Committee Number 5 on 
Chemistry and Chemical Engineering (ARSO/THC 05) . 
 
 
 
 
 
© Afr ican Organisation for Standardisation  2018 — All rights reserved* 
 
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P. O. Box 57363 — 00200 City Square  
NAIROBI, KENYA  
 
Tel. +254 -20-2224561, +254 -20-3311641, +254 -20-3311608  
 
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Web: www.arso -oran.org  
                                                 
* 2018 ARSO — All rights of exploitation reserved worldwide for African Member States’ NSBs. 
 DARS  1488:2018  
iv © ARSO 2018 — All rights reserved   
 
Copyright notice  
 
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© African Organisation for Standardisation 2018 — All rights reserved  
 
ARSO Central Secretariat  
International House 3rd Floor  
P.O. Box 57363 — 00200 City Square  
NAIROBI, KENYA  
 
Tel: +254 -20-2224561, +254 -20-3311641, +254 -20-3311608  
 
 
E-mail: arso@arso -oran.org  
Web: www.arso -oran.org  
 
Reproduction for sales purposes may be subject to royalty payments or a licensing agreement. 
Violators may be p rosecuted.  
 
 
 DARS 14 88:2018  
© ARSO 2018 — All rights reserved  1  
Potassium sulphate (sulphate of potash) fertilizer — Specification  
 
 
1 Scope  
 
This African Standard specifies  the requirements, sampling and methods of test for potassium sulphate 
(sulphate of potash) fertilizer  
 
2 Normative references  
 
The following referenced documents are indispensable for the application of this document. For dated 
references, only the edition cited applies. For undated references, the latest edition of the referenced 
document (including any amendments) applies.  
 
AOAC Official Method 928.02, Chlorine (water -soluble) in fertilizers  
 
AOAC Of ficial Method 980.02, Sulfur in fertilizers — Gravimetric method  
 
AOAC Official Method 983.04, Sodium in fertilizers — Atomic absorption spectrophotometric method  
 
AOAC 2006.03 , Arsenic, cadmium, cobalt, chromium, lead, molybdenum, nickel, and selenium in 
fertilizers  — Microwave digestion and inductively coupled plasma -optical emission spectrometry  
 
EN 12048, Solid fertilizers and liming materials — Determination of moisture content — Gravimetric 
method by drying at 105 2 C 
 
EN 15477, Fertilizers — Determi nation of the water -soluble potassium content  
 
EN 15925, Fertilizers — Extraction of total sulfur present in various forms  
 
EN 16032, Fertilizers — Extraction and determination of elemental sulfur  
 
EN 16195, Fertilizers — Determination of chlorides in the absence of organic material  
 
ISO 7409, Fertilizers — Marking — Presentation and declarations  
 
ISO 8157, Fertilizers and soil conditioners — Vocabulary  
 
ISO 8397, Solid fertilizers and soil conditioners — Test sieving  
 
ISO 14820 -1, Fertilizers and liming ma terials — Sampling and sample preparation — Part 1: 
Sampling  
 
ISO 14820 -2, Fertilizers and liming materials — Sampling and sample preparation — Part 2: Sample 
preparation  
 
ISO 17318, Fertilizers and soil conditioners — Determination of arsenic, cadmium, ch romium, lead 
and mercury contents  
 
ISO 17319, Fertilizers and soil conditioners — Determination of water -soluble potassium content — 
Potassium tetraphenylborate gravimetric method  
 
3 Terms and  definitions  
 
For the purpose of this standard , the terms and de finitions in ISO 8157  apply.  
 
 AFRICAN STANDARD  DARS 14 88:2018  
2 © ARSO 2018 — All rights reserved  4 Requirements  
 
4.1 General d escription  
 
The fertilizer shall be in the form of free flowing  crystalline  powder and free from visible contamination.  
 
4.2 Physical  requirements  
 
When tested accordance with ISO 8397 ,the partic le size shall be such that not less than  65 % of the 
material shall pass through 1.7 mm IS sieve and be retained on 0.25 mm IS sieve.  
 
4.3 Chemical  requirements  
 
The fertilizer shall comply with requirements/limits given in Table 1 when tested according to  the methods 
specified therein.  
 
Table 1— Chemical requirements  
 
Sl. No. Characteristic  Requirement  Test method  
i) Potash content (as K 2O), % m/m, min.  50.0 ISO 17319/ EN 15477  
ii) Sulphur as S , % m/m, min.  17.5 AOAC  980.02 / EN 16032 / 
EN 15925  
iii) Sodium chloride (as NaCl), % m/m, max.  2.0 AOAC 983.04  
iv) Total Chloride as Cl , %m/m,  max 2.5 AOAC  928.02 / EN 16195  
iv) Moisture, % m/m, max.  1.5 EN 12048  
 
4.4 Heavy metal contaminants  
 
The heavy metal contaminants, if present, shall not exceed the limits  stipulated in Table 2.  
 
Table 2 — Heavy metal contaminants  
 
SNo.  Parameter  Maximum limit,  mg/kg  Test method  
i)  Arsenic, As  10.0 ISO 17318  
ii)  Cadmium, Cd  7.0 ISO 17318  
iii)  Mercury, Hg  0.1 ISO 17318  
iv)  Selenium, Se  1.0 AOAC 2006.03  
v)  Lead, Pb  30.0 ISO 17318  
vi)  Chromium, Cr, max.  50.0 ISO 17318  
 
5 Sampling  
 
Sampling shall be carried out in accordance with ISO 14820 -1. 
 
6 Tests  
 
6.1 Methods of test  
 
Samples of the fertilizer  shall be prepared in accordance with ISO 14820 -2 and tested in  accordance 
with the method s of test indicated in  Table 1  and Table 2 . 
 DARS 14 88:2018  
© ARSO 2018 — All rights reserved  3 6.2 Inspection  
 
From the bulk sa mples obtained from ISO 14820 -1, inspect the lot for the characteristics relating  to 
the packing and marking of the product.  
 
7 Com pliance  
 
The lot shall be deemed to comply with the standard  if after inspection and testing it complies with the  
require ments of this standard.  
 
8 Packaging and labelling  
 
8.1 Packaging  
 
The fertiliser shall be packed in clean, non -defective and strong containers.  The material for which the 
container i s made shall be such as to protect the contents from moisture and also not lead to easy 
rupture during handling, transportation and storage.  
 
8.2 Labelling  
 
8.2.1  Each container of the fertiliser shall bear a label in indelible marking in accordance with ISO 
7409, the Globally Harmonized System (GHS) and with the following particulars:  
 
a) name, address and physical location of the manufacturer/packer/importer;  
 
b) type of the product as potassium sulphate fertilizer ;  
 
c brand name  
 
d) the minimum potash c ontent, as K 2O, in percentage by mass;  
 
d) the net weight of the fertilizer in the package;  
 
e) handling instructions;  
 
f) storage instructions;  
 
g) manufacture and best before date ; 
 
h) batch/lot number;  
 
i) Country of origin.  
 
j) Instruction s for use  
 
8.2.2 Bulk containers  
 
Where the fertilizer  is distributed in bulk, the marking  information shall acco mpany the delivery notice 
to the purchaser.  
 
9 Certificate of analysis  
 
A certificate of analysis stating the mini mum percentage levels of plant nutrient e lements shall 
accompany every lot or consign ment of  the fertilizer.  
 
10 Material safety  
 
Each container must be accompanied by a Material Safety Data Sheet (MSDS) and Technical Data 
Sheet (TDS).  
 DARS 14 88:2018 
© ARSO 2018 — All rights reserved