DEAS 91 1:2018  
 
© EAS 2018                                                                                                               First Edition 201 8 
 
 
DRAFT EAST AFRICAN STANDARD  
Fertilizer ― Ammonium Sulphate (Sulphate of ammoni a) ― 
Specification  
EAST AFRICAN COMMUNITY     
 
 
  
 Foreword  
Development of the East African Standards has been necessitated by the need for harmonizing requirements 
governing quality o f products and services in the East African Community. It is envisaged that through 
harmonized standardization, trade barriers that are encountered when goods and services are exchanged 
within the Community will be removed.  
In order to achieve this object ive, the Community established an East African Standards Committee mandated 
to develop and issue East African Standards.   
The Committee is composed of representatives of the National Standards Bodies in Partner States, together 
with the representatives fro m the private sectors and consumer organizations. Draft East African Standards 
are circulated to stakeholders through the National Standards Bodies in the Partner States. The comments 
received are discussed and incorporated before finalization of standar ds, in accordance with the procedures 
of the Community.  
East African Standards are subject to review, to keep pace with technological advances. Users of the East 
African Standards are therefore expected to ensure that they always have the latest versions o f the standards 
they are implementing.   
© EAC  2018 – All rights reserved  Fertilizer ― Ammonium Sulphate  (Sulphate of ammoni a) ― 
Specification  
1 Scope  
This Draft East African standard specifies  requirements, methods of sampling and test for ammonium 
sulphate fertilizer.  
2 Normative referen ces 
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.  
ISO 8157 , Fertilizers and Soil Conditioners – Vocabulary  
DEAS 913, Fertilizers – Methods of sampling   
ISO 17318 , Fertilizers and soil conditioners -- Determination of arsenic, cadmium, chromium, lead and 
mercury contents . 
ISO 8397 , Solid fertilizers and so il conditioners – Test sieving   
ISO 5314 , Fertilizers – Determination of ammoniacal nitrogen content – Titrimetric method after distillation  
ISO 10084 , Solid fertilizers – Determination of mineral Acid -soluble Sulphate – Gravimetric Method  
3 Terms  and Definitions  
For the purpose of this standard, terms and definitions given in ISO 8157  shall apply.  
4. Requirements  
4.1 Physical  
Fertilizer shall be in the form of a free -flowing granules or crystals, free from foreign matter and impurities. The 
colour of the fertilizer shall be uniform. When tested by ISO 8397 , not less than 90 percent by weight of the 
material shall be of particles in the size range of 1 mm to 4 mm for crystal s and 2mm to 5mm for granules.  
4.2 Chemical  
The Sulphate of Ammonia fertilizer shal l comply with the requirements given in Table 1.  
Table 1 ― Requirements for ammonium sulphate fertilizer  
Characteristic  Requirement  Method of Test  
Ammoniacal nitrogen (as N) % by mass, min . 20 ISO 5314  
Free acidity (as H2SO4) % by mass, max . 0.03 Annex B  
Sulphur (as S) % by mass, min . 23 ISO 10084  
  
  5 Heavy m etal contaminants  
Heavy metal contaminants in the fertilizers shall conform to the limits given in Table 2 when tested with the 
method specified therein.  
Table 2 – Requirements for heavy metal contaminants  
Heavy metal  Requirement  Method of test  
Arsenic , mg/kg, max . 20 
ISO 17318  Cadmium , mg/kg, max.  7 
Mercury , mg/kg, max . 0.1 
Lead , mg/kg, max.  30 
Chromium , mg/kg, max.  500 
6 Sampling  
Sampling of fertilizer shall be carr ied out in accordance with  DEAS 913.  
7 Packaging and labelling  
7.1 Packaging  
The fertilizer shall be packaged in materials that are clean and non -defective that protect s the product from 
physical, chemical and moisture contamination and withstand multiple stages of handling (transportation and 
storage).  
7.2 Labelling  
Each package  shall be indelibly labeled in English and/or any other language with the following information:  
a) name of the fertilizer i.e. "ammonium sulphate fertilizer;  
b) name and address of the manufacturer and importer;  
c) nutrient contents;  
d) net content by mass in kg;  
e) handlin g instructions – including the words “Use No hooks”;  
f) production date and expiry date;  
g) country of  origin ; 
h) batch number ; and  
i) storage conditions .  
© EAC  2018 – All rights reserved  Annex A  
(normative)  
 
Determination of moisture content  
A.1 Oven dry method  
A.1.1  General  
The method does not appl y to fertilizers that yield volatile substances other than water at drying temperature.  
A.1.2  Procedure  
A.1.2.1  Weigh accurately 2 g of the prepared sample in a pre -weighed, clean and dry weighing bottle or 
petridish.  
A.1.2.2  Heat in an oven for about 5 ho urs at 105 + 20C to constant weight. Cool in a desiccator and 
weigh. For urea, heat at 70 + 50C for 5 hours to constant weight.  
A.1.3  Calculation  
Moisture per cent by weight (%) = 
ABCB

100 where,  
A is the w eight in gram of the empty bottle ; 
B is the we ight of the bottle plus the material in gram, before drying ; 
C is the  weight of the bottle plus the material in gram, after drying . 
A.2 Vacuum desiccator method  
A.2.1  General  
The method is applicable to Ammonium Chloride, Calcium Ammonium Nitrate  (CAN), Di -Ammonium 
Phosphate (DAP) and all types of complex and mixtures of NPK fertilizers.  
A.2.2 Procedure  
Weigh accurately in duplicate 5g of prepared sample in a weighed shallow porcelain dish. Put the sample in a 
desiccator over concentrated sulphuri c acid, close and introduce vacuum for about 10 minutes, then stop the 
vacuum pump and leave the sample for 24 hours, then release vacuum, remove the sample from the 
desiccator and weigh.  
A.2.3 Calculation  
Moisture per cent by weight = 
) () (
100
1 23 2
W WW W

  
where,  
W1 is the w eight in gram of empty porcelain dish ;  
  W2 is the w eight in gram of porcelain dish with sample before putting the sample for 24 hours in the 
desiccator ; 
W3 is the w eight in gram of porcelain dish with sample after putting the sample fo r 24 hours in the 
desiccator . 
A.3 Karl Fischer method  
A.3.1  General  
This method is applicable to fertilizers like CAN, Urea and urea based complexes. This method is not suitable 
for phosphate rock based fertilizers and fertilizers containing monocalcium ph osphate, calcium sulphate, alkali 
carbonates as well as aldehydes and ketone groups.  
A.3.2  Apparatus  
Karl Fischer titrator  
A.3.3  Reagents  
A.3.3.1  Karl Fischer reagent  (KF) – Karl Fischer solution (pyridine free) (single solution)  
A.3.3.2  Di-sodium tartarat e dihydrate (Na 2C4O62H2O) analytical grade  
A.3.3.3  Methanol -KF grade/spectroscopy grade containing less than 0.05 % water  
A.3.4  Procedure  
A.3.4.1  Standardization of KF reagent  
A.3.4.1,1  Set up the instrument as per manufacturer’s manual.  
A.3.4.1.2  Add me thanol to the titration vessel until the electrodes are dipped and titrate with Karl -Fischer 
reagent to a pre -set end point persists for 30 seconds.  
A.3.4.1.3  Add 100mg of the disodium tartarate dehydrate to the titration vessel carefully and titrate with Karl 
Fischer reagent to a pre -set end point (the pre -set end point should persist for 30 seconds). Note the volume 
of KF reagent used as V 1 ml. 
A.3.4.2  Determination of moisture of sample  
A.3.4.2  Weigh accurately 1 g of the prepared sample and transfer to the titration vessel carefully and stir 
until dispersed.  
A.3.4.2  Titrate with KF reagent to the same pre -set end point as above and note the volume of KF 
reagent used as V 2 ml. 
A.3.5  Calculation  
Factor (F)(mgH 2O/1 ml of KF reagent ) = 
1added dihy drate tartarate sodiumofmg 0.1566
V  
Moisture per cent by weight = 
0001 (gram) sampleof Weight100 2
VF   
© EAC  2018 – All rights reserved  Annex B  
(normative)  
 
Determination of free acidity  
B.1 Part 1 : Determination of free acidity as H 2SO 4 
B.1.1  Reagent  
B.1.1.1  Standard sodium hydroxide solution – 0.02 N  
B.1.1.2  Methyl red -methylene blu e mixed indicator solution – prepared by mixing equal volumes of 0.2% 
solution in rectified spirit of methyl red and 0.1  % solution in rectified spirit of methylene blue.  
B.1.2  Procedure  
B.1.2.1  Dissolve 20  g of the sample in about 50  ml of cold neutral w ater.  
B.1.2.2  Filter and make up the volume to about 200  ml. The filtering media shall be neutral and shall not 
contain any alkaline material which would neutralize the free acidity.  
B.1.2.3  Titrate the solution with standard NaOH solution using one or tw o drops of methyl red -methylene 
blue mixed indicator and a microburette.  
B.1.3  Calculation  
Free sulphuric acid (as H 2SO 4) % by mass  = 
WVN 4.904  
where. 
N is the n ormality of standard NaOH solution ; 
V is the v olume in milliliter ( ml) of standar d NaOH solution ; 
W is the w eight in gram (g) of sample taken for the test . 
B.2 Part 2:  Determination of free acidity as HNO 3 
B.2.1  Reagent  
B.2.1.1  Standard sodium hydroxide solution – 0.02 N  
B.2.1.2  Methyl red -methylene blue indicator solution – prepared b y mixing equal volumes of 0.2  % methyl 
red solution in alcohol and 0.1  % methyl blue solution in alcohol  
B.2.2  Procedure  
B.2.2.1  Dissolve 10  g of the sample in 100  ml of neutral water at room temperature in a beaker or conical 
flask.  
B.2.2.2  Filter and ad d 2-3 drops of indicator solution   
  B.2.2.3  Titrate the solution with standard NaOH solution until the colour changes from violet to green  
B.2.3  Calculation  
Free Nitric acid (as H)(HNO 3) % by mass  = 
WVN 4.904  
where;  
N is the n ormality of stand ard NaOH solution ; 
V is the v olume in milliliter ( ml) of standard NaOH solution ; 
W is the w eight in gram (g) of sample taken for the test . 
B.3 Part 3: Determination of free acidity as P 2O5 
B.3.1  Reagents  
B.3.1.1  Acetone  
B.3.1.2  Standard sodium hydroxide s olution – 0.1 N  
B.3.1.3  Bromo cresol green indicator solution – Dissolve 0.1  g bromocresol green in 100mL of rectified 
spirit  
B.3.2  Procedure  
B.3.2.1  Weigh accurately about 2.5  g of the prepared sample in a 250mL Erlenmeyer flask  
B.3.2.2  Add 100  ml neutral acetone. Shake for one hour.  
B.3.2.3  Filter rapidly through whatman filter paper No.1 in to 250  ml Erlenmeyer flask. Wash four times 
with 10mL portion of acetone  
B.3.2.4  Evaporate acetone as far as possible  
B.3.2.5  Add about 50  ml water and drops o f bromocresol green indicator  
B.3.2.6  Titrate with standard NaOH solution, until the colour changes from yellow to blue  
B.3.3  Calculation  
Free phosphoric acid (as P 2O5) % by mass  = 
WVN1.7  
where;  
N is the n ormality of standard NaOH solution ; 
V is the v olume in milliliter (mL) of standard NaOH solution ; 
W is the m ass in gram (g) of sample taken for the test .