PUBLIC REVIEW DRAFT DRAFT UGANDA STANDARD  
  DUS DEAS 904 
First  Edition  
2018-mm-dd 
 
 Reference number  
DUS DEAS 904: 2018 
© UNBS 201 8 
  
Fertilizer — Phosphate rock powder — Specification  
 PUBLIC REVIEW DRAFTDUS DEAS 904:2018 
ii                © UNBS  2018 - All rights reserved 
 Compliance with this standard does not, of itself confer immunity from legal obligations  
A Uganda Standard does not purport to include all necessary provisions of a contract. Users are 
responsible for its correct application  
© UNBS 2018 
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 PUBLIC REVIEW DRAFTDUS DEAS 904:2018 
© UNBS  2018 - All rights reserved                iii National foreword 
Uganda National Bureau of Standards (UNBS) is a parastatal under the Ministry of Trade, Industry and 
Cooperatives established under Cap 327, of the Laws of Uganda, as amended.  UNBS is mandated to co-
ordinate the elaboration of standards and is  
(a) a member of International Organisation for Standardisation (ISO) and  
(b) a contact point for the WHO/FAO Codex Alimentarius Commission on Food Standards, and  
(c) the National Enquiry Point on TBT Agreement of the World Trade Organisation (WTO). 
The work of preparing Uganda Standards is carried out through Technical Committees. A Technical 
Committee is established to deliberate on standards in a given field or area and consists of representatives of 
consumers, traders, academicians, manufacturers, government and other stakeholders. 
Draft Uganda Standards adopted by the Technical Committee are widely circulated to stakeholders and the 
general public for comments. The committee reviews the comments before recommending the draft standards 
for approval and declaration as Uganda Standards by the National Standards Council.  
This Draft Uganda Standard, DUS DEAS 904: 2018 , Fertilizer — Phosphate rock powder — Specification,  is 
identical with and has been reproduced from a Draft East African Standard, DEAS 904:2018 , Fertilizer — 
Phosphate rock powder — Specification,  and is being proposed for adoption as a Uganda Standard. 
This standard was developed by the Food and agriculture  Standards Te chnical Committee (UNBS/TC 2). 
Wherever the words, “ East African Standard" appear, they should be replaced by "Uganda Standard." 
 
  PUBLIC REVIEW DRAFT DEAS 904:2018  
 
© EAS 2018                                                                                                               First Edition 2 018 
 
 
DRAFT EAST AFRICAN STANDARD  
Fertilizer  — Phosphate rock powder — Specification  
EAST AFRICAN COMMUNITY  PUBLIC REVIEW DRAFTDEAS 904:2018  
© EAC 2018 – All rights reserved  Foreword  
Development of the East African Standards has been necessitated by the need for 
harmonizing requirements governing quality of products and serv ices 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 objective, 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 from the private secto rs 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 standards, in accordance wit h 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 of the standards they are implementing .  PUBLIC REVIEW DRAFTDEAS 904:2018  
  Fertilizer  — Phosphate rock powder  — Specification  
1 Scope  
This Draft East African Standard specifies  requirements, methods of sampling and test for 
phosphate rock fertilizers in powder form of biogenic sedimentary origin.  
2 Normative R eferences  
The following referenced standards are indispensa ble for the application of this  standard. For 
dated references, only the edition cited applies. For undated references, the latest edition of 
the referenced standard (in cluding any amendments) appl ies: 
ISO 8157 , Fertilizer – Terminology and Vocabullary  
DEAS 913, Fertilizer  – Methods of sampling  
ISO 17318 , Fertilizers and soil conditioners -- Determination of arsenic, cadmium, chromium, 
lead and mercury contents  
ISO 8397 , Solid fertilizers and soil c onditioners – Test sieving  
3 Terms and definitions  
For the purpose of this East African  standard, the following terms and definition shall apply 
together with those given in ISO 8157 ; 
3.1 
biogenic sedimentation  
biogenic sedimentation – is the deposition by  settling of a suspended material which may be 
either constituents, or secretions of plants or animals produced by life processes.  
4 Requirements  
4.1 General requirements  
4.1.1  Physical  
The fertilizer material shall consist of phosphate rock from natural deposits in the form of free -
flowing powder. The colour of the phosphate rock powder fertilizer shall be uniform.  
4.1.2  Particle size  
The particle size shall be such that at least 90 % of the fertilizer materials pass through 0.15 
mm sieve and not more th an 10 % of the remaining material shall pass through 0.25 mm 
sieve. The fertilizer sample shall be determined by the method given in ISO 8397 . 
4.1 Specific requirements  
Phosphate rock powder fertilizer shall comply with the requirements prescribed in Table 1. PUBLIC REVIEW DRAFTDEAS 904:2018  
© EAC 2018 – All rights reserved  Table 1 Requirements for Phosphate rock powder  
Characteristic  Requirement  Method of test  
 
Total phosphates, (as P 2O5), % by 
mass, min  28.0 Annex A (I)  
Citric acid soluble phosphorus (as 
P2O5) % by mass, min. 9 Annex A (II)  
Calcium content (as CaO) %  by mass, 
min. 35 Annex B  
Moisture, percent by mass, max.  5 Annex C  
 
5 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 m etal contaminants  
Heavy metal  Requirement  Method of test  
Arsenic , mg/kg, max . 20 
ISO 17318  Cadmium , mg/kg  P2O5, max.  60 
Mercury , mg/kg, max . 0.1 
Lead , mg/kg, max.  30 
Chromium , mg/kg, max.  500 
 
5.2 The radioactive elements found in the fertilizer  materials shall not exceed the limit set  
by the respective country.  
6 Sampling  
Sampling of Phosphate R ock Powder fertilizer shall be carried out as prescribed in DEAS 913  
7 Packaging, and labelling  
7.1 Packaging  
The fertilizer shall be packaged in materia ls 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. common name and brand name ; 
b) name and address of the manufacturer/packer ; PUBLIC REVIEW DRAFTDEAS 904:2018  
  c) net content by mass, in kilogram (kg) or tonnes (weight or mass) ; 
d) nutrient content, i.e. total phospho rus (% P 2O5) by mass;  
e) country of origin ; 
f) handling  instructions, including the words such as “use no hooks” ; 
g) production date ; 
h) batch number ; and  
i) storage conditions . PUBLIC REVIEW DRAFTDEAS 904:2018  
© EAC 2018 – All rights reserved  Annex A  
(normative)  
 
Determination of total phosphorus  
A.1 Reagents  
For the purpose of this E ast African Standard, only analytical grade reagents and distilled 
water given below shall be used : 
a) Concentrated hydrochloric acid ; 
b) Concentrated nitric acid ; 
c) Magnesium nitrate solution ; 
d) Citric molybdic acid reagent ; 
e) Quinoline solution ; and  
f) Quimociac reagen t. 
NOTE  All the reagents above can be prepared as described below;  
A. Magnesium nitrate solution – Dissolve 950 g of P -free Mg (NO 3)2.6H2O in water and  
dilute to 1 L.  
B. Citric molybdic acid reagent  – Dissolve 54 g of 100% molybdic anhydride (MoO 3) and  12 
g NaO H with stirring in 400 mL hot water and cool. Dissolve 60 g citric acid in mixture of 
140 mL HCl and 300 mL water and cool. Gradually add molybdic solution to citric acid 
solution while stirring. Cool, filter and dilute to 1 L (solution may be green or blu e colour, 
depending on exposure to light). If necessary, add 0.5 % KBrO 3 solution drop by drop 
until green colour becomes pale. Store in dark polyethylene bottle.  
C. Quinoline solution – Dissolve 50 mL synthetic quinoline while stirring in mixture of 60 mL  
HCl and 300 mL water. Cool, dilute to 1 L and filter. Store in polyethylene bottle.  
D. Quimociac reagent – Dissolve 70 g of sodium molybdate dihydrate in 150 mL water.  
Dissolve 60 g citric acid in mixture of 85 mL HNO 3 and 150 mL water and cool.  
Gradually add  sodium molybdate solution to citric acid -nitric acid mixture while stirring ( A). 
Dissolve 5 mL synthetic quinoline in mixture of 35 mL HNO 3 and 100 mL water ( B). 
Gradually add this solution ( B) to solution ( A), mix and let it stand for 24 h. Filter, add 2 80 
mL acetone, dilute to 1 L with water and mix well. Store in polyethylene bottle.  
A.2 Procedure  
For cases where preparation of reagents should be needed; the following procedures should 
be followed:  
Weigh 1 g of sample, treat with 15 -30 mL concentrated  hydrochloric acid and 3 -10 mL 
concentrated nitric acid and digest till brown fumes cease, then dilute to 200 mL. Pipette into 
500 mL Erlenmeyer flask, aliquot containing not more than 25 mg P 2O5, dilute to 
approximately 100 mL with water. Proceed with one  of the following methods:  
A. Add 30 mL citric molybdic acid reagent and boil gently for 3 minutes (solution must be  
precipitate free at this stage). Remove from heat and swirl carefully. Immediately add from 
burette 10 mL quinoline solution with continuou s swirling (add first 3 -4 mL drop wise and 
remainder in steady stream) or  
B. Add 50 mL quimociac reagent, cover with watch glass, place on hot plate in well -ventilated  
hood and boil for one minute.  
After treatment with either A or B, cool to room temperatu re; swirl carefully 3 -4 times during PUBLIC REVIEW DRAFTDEAS 904:2018  
  cooling. Filter into crucible with glass fibre filter paper or sintered glass crucible grade 4 (30 
mL capacity), previously dried at 250 oC and weighed and washed five times with 25 mL of 
water. Dry crucible and content s for 30 minutes at 250 oC. Cool in a desiccator to a constant 
weight and weigh.  
A.3 Calculation  
0.03207 x (A – B) x F x 100  
Total phosphorus (as P 2O5) % by mass =  
W 
 
where,  
A = Weight of sample precipitates in gram;   
B = Weight of sample precipitates in  gram for 
blank;  
W = Weight of sample;   
F = Dilution factor.  
 
 
II. Determination of citric acid soluble phosphorus content  
 
a) REAGENTS  
For the purpose of this East African  Standard, only analytical grade reagents and distilled 
water shall be used.  
a) Standard phosphate solution – Dilute 50 mL of stock phosphate solution to 250 mL with 
water (1 mL of this solution is equivalent to 0.2 mg P 2O5).  
b) Vanado -molybdate reagent – Dissolve separately 20 g of ammonium molybdate and 1 g of 
ammonium vanadate in hot water. C ool, mix and acidify with 140 mL concentrated nitric acid 
and dilute to 1 L.  
 
b) STANDARDIZATION OF INSTRUMENT  
 
Measure from a burette, into a series of 100 -mL volumetric flasks, 25.0 mL, 26.0 mL, 27.0 mL, 
28.0 mL, 29.0 mL, 30.0 mL, and 31.0 mL of the stand ard phosphate solution containing 5.0 
mg, 5.2 mg, 5.4 mg, 5.6 mg, 5.8 mg, 6.0 mg and 6.2 mg of P 2O5 respectively. Within five 
minutes for the entire series, add 25 mL of the vanadomolybdate reagent into each flask and 
dilute to 100 mL, ensuring that the te mperature of the reagent and dilution water is maintained 
at 27 + 2 oC. Mix and allow to stand for ten minutes.  
If a single beam spectrophotometer is used, set the spectrophotometer to a wavelength of 
420 nm, fill two 1 -cm cells with the standard solution containing 5.0 mg P 2O5 to which the 
vanadomolybdate reagent has been added as given above and check the absorbance of the 
cells. If there is a small difference, select the cell with the lower reading as the standard 
reference cell.  
Using the other cell (sa mple cell), determine the apparent absorbance at 27 + 2 oC (corrected 
for cell differences) of the other standard solutions containing 5.2 mg, 5.4 mg, 5.6 mg, 5.8 mg, 
6.0 mg and 6.2 mg of P 2O5 referred to the solution containing 5.0 mg P 2O5 as the standard . 
After each determination, empty and refill the cell containing the 5 -mg standard solution and 
readjust to zero absorbance to avoid errors that might arise from temperature changes. Plot a 
calibration graph of absorbance against concentration in mg P 2O5 per 100 mL of standard 
solution.  
NOTE – In the preparation of the standard phosphate solution, add to each flask, a volume of citric acid 
equal to the amount contained in the diluted sample solution mentioned in 5.1 (a) prior to the addition of 
the vanadomo lybdate reagent.  
 
c) DISSOLUTION OF SAMPLE  
Weigh 1 g of prepared sample into a 250 -mL conical flask, add 100 mL of freshly prepared 2 
per cent citric acid, stopper and shake for 30 minutes using a mechanical shaker (set a -
shaking speed of twice per second),  filter immediately.  
 
d) PROCEDURE  
A. Successively dilute a portion of the solution (volume V1 mL) prepared as in 5.1.2 , so that a 
final volume of about 25 mL contains between 5.5 mg P 2O5 and 6.2 mg P 2O5, taking care PUBLIC REVIEW DRAFTDEAS 904:2018  
© EAC 2018 – All rights reserved  that the dilution water is at 27 + 2oC.  
B. Transfer this solution to a 100 -mL volumetric flask, add 25 mL of the vanadomolybdate 
reagent (at a temperature of 27 + 2oC), dilute to the mark, mix and allow to stand for 10 
minutes. At the same time, transfer 25 mL of the standard phosphate solution (at 27  + 2oC) 
into a second 100 -mL volumetric flask. Add sufficient citric acid such that when the   
solution is made up to 100 mL, its concentration is equal to that of the diluted sample solution. 
Add 25 mL of vanadomolybdate reagent at 27 + 2oC, dilute to ma rk, mix and allow to stand 
for 10 minutes.  Measure the diff erence in absorbance at 27 + 2oC between the two solutions 
and estimate the P2O5 content of the sample solution using the calibration graph.  
 
e) CALCULATION  
Y     100       100 
Citric acid soluble P 2O5 content % by mass =      
1000 V1 M 
where,   
Y = graph reading, in mg/100 mL;   
V1 = volume (in mL) of sample solution diluted for test; 
M = mass (in gram) of the sample.   PUBLIC REVIEW DRAFT 
  Annex B  
(normative)  
 
Determination of calcium oxide  
B.1 Reagents  
For the purpos e of this East African Standard, only analytical grade reagents and distilled 
water shall be used . 
a) Concentrated hydrochloric acid.  
b) Concentrated nitric acid.  
c) Hydrofluoric acid – 40% 
d) Sodium carbonate – solid 
e) Dilute hydrochloric acid – 1:1 (v/v)  
f) Ammonium ch loride – solid 
g) Dilute acetic acid – 1:1 (v/v)  
h) Ammonium oxalate – solid 
i) Oxalic acid solution – 1g/L (m/v)  
j) Dilute sulphuric acid 1:4 (v/v)  
k) Standard potassium permanganate solution (0.1 N) – Dissolve3.2g of potassium 
permanganate in 1 litre of water. Let stan d in the dark overnight. Filter, without 
washing, through glass wool. Avoid contact with rubber or other organic material. 
Store in a dark -coloured glass -stoppered bottle. Standardized against standard 
sodium oxalate.  
B.2 Procedure  
For cases where prepara tion of reagents should be needed; the following procedures should 
be followed:  
B.2.1  Transfer 0.5g of sample that has been dried at 105 0C to a 400 -mL tall from beaker. 
Dissolve, by boiling gently with 20ml of concentrated hydrochloric acid and 10ml of 
concentrated nitric acid, until the volume is reduced to about 10ml. Covering the beaker by 
watch -glass throughout the process of dissolution, add 20ml of concentrated nitric acid and 
then evaporate to a small volume. Wash the lower surface of the watch -glass into beaker with 
hot water, filter and wash collecting the filtrate and washings in a 250ml measuring or 
volumetric flask. Preserve the filter and washings.  
B.2.2  Dry the residue and burn off the filter paper by ignition in a platinum crucible. Moisten 
the cooled residue with a few drops of a concentrated nitric acid and add about 10ml of 
hydrofluoric acid. Evaporate continuously just to dryness, ignite and fuse the residue with 
about 2 to 3 g of sodium carbonate. Extract the melt in about 25 -30ml of dilu te hydrochloric 
acid in a beaker, evaporate to dryness and bake. Extract the baked mass with about 10ml of 
concentrated hydrochloric acid, dilute, filter and wash collecting the filtrate and washings in PUBLIC REVIEW DRAFT 
© EAC 2018 – All rights reserved  the same volumetric flask where in the first filtrate  along with washings has been preserved 
under 5.1. Cool the combined filtrates and make up to the mark.  
B.2.3  Pipette out exactly 100ml from the solution in the volumetric flask under 5.2 into 
400ml -beaker. Add sufficient ammonium chloride (about 15ml) to hold magnesium in solution 
in presence of ammonium oxalate. Add 20ml of dilute acetic acid, heat to boiling point and 
add about 2g of ammonium oxalate whi le stirring. Boil and allow the precipitate to settle for 1 
to 2 hours, cool and filter the solution t hrough a close filter paper. Wash the precipitate with 
hot water until free from oxalate.  
B.2.4  Dissolve the precipitate on the filter in about 50ml of hot dilute hydrochloric acid. 
Wash the filter thoroughly with hot water until the filter is free from a cid and collect the 
washings also in the same beaker in which calcium was first precipitated. Reduce the bulk to 
about 100ml by evaporation and re -precipitate calcium as oxalate under 5.3  
B.2.5  Wash the precipitate of calcium oxalate into same beaker in wh ich precipitation was 
first carried out and treat the filter with about 25ml of warm (70 to 800C) dilute sulphuric acid 
for dissolving adhering precipitate of calcium oxalate. Wash the filter free from acid by means 
of hot water. Collect the washings also in the same beaker into which the precipitate was 
transferred. Add about 25ml more of dilute sulphuric acid and raise the temperature of 
contents to about 700C. When the precipitate has dissolved, titrate with standard potassium 
permanganate solution until  a permanent pale pink colour persists in solution.  
B.3 Calculation  
Calcium oxide % =
CFBA 100 (0.028)   
where,  
A is the  volume (in ml) of standard potassium permanganate solution ; 
B is the  normality of the standard potassium permanganate solution ; 
C is the m ass (in gram) of the sample represented by the aliquot taken ; 
F is the d ilution factor . PUBLIC REVIEW DRAFT 
  Annex C 
(normative)  
 
Determination of moisture content  
C.1 Oven dry method  
C.1.1  General  
The method does not apply to fertilizers that yield volatile substances  other than water at 
drying temperature.  
C.1.2 Procedure  
C.1.2.1  Weigh accurately 2 g of the prepared sample in a pre -weighed, clean and dry 
weighing bottle or petridish.  
C.1.2.2  Heat in an oven for about 5 hours at 1050C + 20C to constant weight. Cool in a 
desiccator and weigh. For urea, heat at 700C + 50C for  five hours to constant weight.  
C.1.3 Calculation  
Moisture per cent by weight (%) =  
ABCB

100  
where,  
A is the weight in gram of the empty bottle;  
B is the weight of the bottle plus the m aterial in gram, before drying;  
C is the weight of the bottle plus the material in gram, after drying . 
C.2 Vacuum desiccator method  
C.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.  
C.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 sulphuric 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.  
C.2.3 Calculation  
Moisture per cent by weight = 
) () (
100
1 23 2
W WW W

  PUBLIC REVIEW DRAFT 
© EAC 2018 – All rights reserved  where,  
W1 is the Weight in gram of empty porcelain dish ; 
W2 is the Weight in gram of porcelain dish with sample before putting the sample for 24 
hours in the desiccator ; 
W3 is the Weight in gram of porcelain dish with sample after putting the sample for 24 
hours in the desiccator . 
C.3 Karl Fischer method  
C.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 phosphate, calcium sulphate, alkali carbo nates as well as aldehydes and 
ketone groups.  
C.3.2 Apparatus  
Karl Fischer titrator  
C.3.3 Reagents  
C.3.3.1  Karl Fischer reagent(KF) – Karl Fischer solution (pyridine free) (single solution) . 
C.3.3.2  Di-sodium tartarate dihydrate (Na2C4O62H2O) analytical gr ade  
C.3.3.3  Methanol -KF grade/spectroscopy grade containing less than 0.05 % water . 
C.3.4 Procedure  
C.3.4.1  Standardization of KF reagent.  
C.3.4.1.1  Set up the instrument as per manufacturer’s manual.  
C.3.4.1.2  Add methanol to the titration vessel until t he electrodes are dipped and titrate with 
Karl-Fischer reagent to a pre -set end point persists for 30 seconds.  
C.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. 
C.3.4.2  Determination of moisture of sample  
C.3.4.2.1  Weigh accurately 1 g of the prepared sample and transfer to the titration vessel 
carefully and s tir until dispersed.  
C.3.4.2.2  Titrate with KF reagent to the same pre -set end point as above and note the 
volume of KF reagent used as V2 m l. 
C.3.5 Calculation  
Factor (F)(mgH 2O/1 ml of KF reagent ) = 
1added dihy drate tartarate sodiumofmg 0.1566
V  PUBLIC REVIEW DRAFT 
  Moisture per cent by weight = 
0001 (gram) sampleof Weight100 2
VF