SZNS 006:2011  
 
ICS 71.100.40                  Edition 1  
            
 
 
 
 
 
 
ESWATINI NATIONAL STANDARD  
 
 
Specification for liquid soap  
 
 
 
 
 
 
 
 
 SZNS 006:2011  
Edition 1  
ii           © SWASA 2011  – All rights reserved  
 
Published by: Eswatini Standards Authority  
Marble Construction Building, Plot 247 11th Street King Mswa ti III Avenue West  
P. O. Box 1399, Matsapha, Kingdom of Eswatini  
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Website: www.swasa.co.sz  
E-mail: info@swasa.co.sz   
©Eswatini Standards Authority 2012  
 
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SZNS 006:2011  
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© SWASA 2011  – All rights reserved   iii 
Table of changes  
Clause Changed  Date  Change  
   
 
NATIONAL FOREWORD  
This Eswatini National Standard was prepared by Technical committee SWASA/TC 13 Clothing and 
apparel  in accordance with procedures of the Eswatini Standards Authority, in compliance with 
Annex 3 of the WTO/TBT Agreement.    
During the preparation of this standard assistance was derived from the following documents: 
Kenyan standards KS 03-803: PART 1:1988, Specification for liquid soaps, Part 1: Toilet soap, 
KS 03-803: PART 2:1988, Specification  for liquid soaps, Part 2: Liquid floor soap, KS 09- 
42:1977,  Methods  of analysis  for  soaps  published  by the  Kenya  Bureau  of Standards,  South  
African  standards  SANS 238:2008, Liquid toilet soap, SANS 20825:1993,  Environmentally  
acceptable hand dishwashing  and light duty detergent (liquid) published by the South African 
Bureau of Standards. 
 
 
 
 
 
 
 
 
 
 SZNS 006:2011  
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iv           © SWASA 2011  – All rights reserved  Contents                    Page  
1   Scope ................................ ................................ ................................ ................................ .................  1 
2  Definitions ................................ ................................ ................................ ................................ ..........  1 
3  Application ................................ ................................ ................................ ................................ .........  1 
4   Types of liquid  soap ................................ ................................ ................................ .........................  1 
5.  Requirements ................................ ................................ ................................ ................................ .... 2 
5.1  General Requirements ................................ ................................ ................................ .................  2 
5.2 Chemical  requirements................................ ................................ ................................ ................  2 
6 Packaging and marking ................................ ................................ ................................ ......................  3 
6.1  Packaging ................................ ................................ ................................ ................................ .... 3 
6.2  Marking ................................ ................................ ................................ ................................ ....... 3 
7  Sampling and testing ................................ ................................ ................................ .........................  3 
8  Quality of reagents ................................ ................................ ................................ .............................  4 
9  Standard hard water ................................ ................................ ................................ ...........................  4 
10  Test methods ................................ ................................ ................................ ................................ ..... 4 
10.1   Germicidal activity determination ................................ ................................ ........................  4 
10.2      Stability test................................ ................................ ................................ ...........................  4 
10.3      Determination of total fatty matter ................................ ................................ .......................  5 
10.4     Determination of free alkali and free acid ................................ ................................ ...........  6 
10.5      Determination of number of fatty acids  ................................ ................................ .................  7 
10.6      Determination of rosin  ................................ ................................ ................................ ...........  7 
10.7      Determination of matter insoluble in water ................................ ................................ .........  9 
    10.8        Determination of matter insoluble in alcohol………………………………………………9  
10.9      Determination of chlorides ................................ ................................ ................................ . 10 
10.10       Determination of unsaponified and saponifiable matter ................................ .................  11 
10.11   Determination of borax ................................ ................................ ................................ ....... 13 
10.12    Determination of sulphates ................................ ................................ ................................ . 14 
10.13    Determination of moisture and volatile matter ................................ ................................ .. 15 
Bibliography  ................................ ................................ ................................ ................................ ....... 18 SZNS 006:2011  
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  SZNS 006:2011  
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© SWASA 2011  – All rights reserved   1 Specification for liquid soap 
1   Scope 
This standa rd specifies the requirements and test methods for liquid soap for gene ral cleaning,  but 
not for personal hygiene. 
2   Definitions 
2.1 
Unsaponifiable  matter 
Substances,  such as the  higher  aliphatic  alcohols,  sterols, colouring materials and hydrocarbons, 
which may be present  in soap and which are not capable  of being saponified by caustic alkali but 
are soluble in ordinary fat solvents.  
2.2 
Unsaponified matter                                                        
 
The neutral fat (unsapon ified neutral glycerides)  present  in soap 
2.3 
Ambient room temperature 
The temperature of the surroundi ng air sometimes referred to as room temperature. 
Note: room  temperature is taken to be roughly 21  – 23 ºC; the standard room  temperature is 22 ºC. 
3 Application  
3.1 This standa rd applies  to liquid  soap prepared from suitable  oils completely  sapon ified. 
3.2 The liquid soap to this specification is intended for gene ral cleaning, particularly , the 
cleaning of hard surfaces such as floors, painted  surfaces, lacqu ered surfaces,  and the surfaces of 
equipment. 
3.3 Type 1 soap  (with antimicrobial agents) is intended  for cleaning  surfaces where the destruction 
of micro-organisms is important. 
4   Types of liquid  soap 
Two types  of liquid soap shall  be covered as follows:  
a) TYPE 1 – With antimicrobial agent;  
b) TYPE 2 – Without  antimicrobial agent.  
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5 Requirements  
5.1 General  Requirements 
5.1.1    The soap shall be a stable homogeneous  liquid 
5.1.2    The soap shall be free from objectionable  odou r, both as received and in solution in hot 
water. 
5.1.3    The soap shall contain  no foreign matter. 
5.1.4    The  soap  shall  not  be  irritating  to  the  skin  and  shall  not  contain  ingredients  in 
quantities  that are harmful or toxic to humans. 
5.1.5    The soap shall  have good lathering and clean ing properties and shall  give a clear 
solution  when diluted with water having  a hardness of up to 200 p pm as calcium carbona te. The 
hardness of the water shall  be prepared in acc ordance  with the requirements of clause 8 of this 
standard. 
5.1.6    The   soap   shall   not   damage   the   surface   cleaned   when   properly   used   as 
recommended  by the manufacturer. 
5.1.7    There shall be no visible  change  in the product  when tested in accordance with clause 9.2 
of this standard. 
5.1.8    The product  shall be stable and shall not lose effectiveness  or otherwise  deteriorate  
and shall  meet  the  requirements  of  this  specification  when  retained  in  its  o riginal  unopen ed 
container at ambient  temperatures for a period of one year from date of manufacture. 
5.1.9    The soap shall not leave  any residual taste on washed objects. 
5.2 Chemical  requirements 
5.2.1    Germicidal Activities 
Type 1 soap (with antimicrobial  agent) at a diluti on of 1:80 shall give a positive  100 per cent 
kill, at a confidence  level of 95 per cent (59 out of 60 replicate s),  against  staphylococcus 
aureus, salmone lla  chloraesuis  and pseudo monas  aeruginosa  when tested  in accordance with 
clause  9.1 of this standard. 
5.2.2  The liquid  soap shall  also conform to the chemical requirements given  in Table 1. 
 
 
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© SWASA 2011  – All rights reserved   3 Table 1 Chemical requirements for liquid soap 
 
 Characteristics Requirement Test method 
min. max. 
(i) Total fatty acid,  per cent by mass 22 - Clause  9.3 
(ii) Free alkali as Na2O and free acid,   
% by 
 mass - 0.1 Clause  9.4 
(iii) Free fatty acid, % by mass - 0.1 Clause  9.5 
(iv) Rosin, % by mass - 0.1 Clause  9.6 
(v) pH of 5 % solution  8 10 pH meter-glass elec trode 
(vi) Matter insoluble  in alcohol, - 1.2 Clause  9.7 
(vii) Matter insoluble  in water - 0.2 Clause  9.8 
(viii) Chlorides, calculated as KCl - 0.7 Clause  9.9 
(ix) Sulphates  Trace Clause 9.12 
(x) Unsaponi fied plus unsaponi fiable matter  1.4 Clause 9.10 
(xi) Total water conten t, 
% by mass  70 Clause 9.13 
 
 
 
6 Packa ging and marking 
6.1 Packaging  
The liquid  soap shall be packed in contain ers that are strong enough  to withstand  normal 
usage  and transportation  and will prevent  leakage, drying out and contamination  of the 
product . The container  shall NOT be formulated  or manufactured with  inks,  dyes, pigments 
or any other  additives  that contain  lead, cadmium, mercury or hexavalent  chromium (or any 
combination of these). The individ ual or combined concen tration of contaminates present in 
materials of the container  shall not exceed 250 mg/L. 
 SZNS 006:2011  
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4   © SWASA 2011  – All rights reserved  6.2 Marking  
6.2.1    All information marked on the label  shall be marked in a manner that is conspicuous, 
legible and indelible. 
6.2.2  Each container  shall  be marked with the follo wing particulars:  
a) Name of product  e.g. liquid soap with germicide; 
b) Intended  uses – Marking shall include  type of surfaces to be cleaned  by the product  
without  damaging the surface being cleaned, e.g. ‘for use on concrete painted  and 
unpainted  floor and wall surfaces’ and shall  also include storage conditions  that must be 
avoided;               
 
c) A precautiona ry notice,  which shall  inclu de: 
i. Types of floor and wall surfaces which must not be cleaned  using the 
product; 
ii. ‘ The product  is not for personal  uses’  
d)  Name and address of manufacturer and trade mark;  
e) Batch or code  number; 
f) Net volume or weight  of conten ts in metric units; 
g) Directions for use. 
6.2.3    The container shall  not be marked with the words “Non-toxic”, “Non-poisonous ” or 
similar phrases that might suggest  that the product is sui table for consumption  or harmLess if 
swallowed. 
7 Sampling and testing 
To test for the compliance of this standa rd, samples shall  be drawn from the markets, point of 
manufacture or anywhere else and tested as per this specification. 
8 Quality of reagents 
Unless  otherwise specified, chemicals used shall  be of recogni zed analytical reagent  quality. 
Distilled water or deionized  water shall  be used. 
9 S t a n d a r d  hard water 
Dissolve  3520g  of chemically pure calcium chloride (CaCl2.2H2O) and 3947g of chemically 
pure  magnesium  sulfate  (MgSO4.7H2O)  in distilled  water  and  dilute  to 20L  with  distill ed  SZNS 006:2011  
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© SWASA 2011  – All rights reserved   5 
water. 
NOTE 1: This standard hard water has a  hardness of approximately 200mg/L calculated as calcium 
carbonate. 
10 Te s t methods 
10.1  Germicidal activity determination 
10.1.1 Apparatus  
a) Broth 
b) stainless  steel rings 
10.1.2 Reagents  
Test    culture   prepared   from   staphylococ cus    aureus,   Escherichia    coli, salmonella  
chloraesuis  or pseudomonas  aeruginosa 
10.1.3 Procedure  
Add 5% organic serum with 200 ppm hard water and add it to a test culture in a broth. Place 
clean,  polished  stainl ess steel rings in the broth for 15 minutes at room temperature. The 
contaminated  stainless  steel  rings  are  then  dried  at  37  ±  1  ˚C  for  40  minutes.  The 
contaminated rings  are placed in test tubes that have 10 ± 2 mL of the diluted product  
prepared with 200 ppm hard water. After 10 minutes the rings are placed  in a neutralisation 
media. After a 48 hour incubati on period, each tube is examined for growth. 
10.2     Stability test 
10.2.1 Procedure  
Fill a stoppe red 100 mL cylinder  with a uniform sample of the soap and leave undist urbed for 
72 hours at 30 ± 5 ˚C. Examine the sample for any visible  change.  
10.3     Determination of total fatty matter 
10.3.1 Reagents  
a) Methyl orange indica tor – Dissolve  0.1g in 100 mL of water 
b) Ethyl Ether- Pure 
c) Sodium  Chloride Solution  – Saturated 
d) Acetone  
e) Sulphu ric Acid – 4 D solution  SZNS 006:2011  
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10.3.2   Procedure 
Weigh 50 ± 0.01g  of the sample and dissolve  in 500 mL of hot water until completely dissolved 
(The  presence  of  synthetic  detergents  shall  be  suspec ted  if  clean  separation  and  clear  
ethereal layers are not obtained  during the initial  ether  extraction). Transfer  the solution  into a 
separator. Wash down the vessel containing  the soap solution  with small quantities  of hot water 
and add the washings to the separator. Add a few drops of the methyl orange  indicator and from a 
burette add slowly a quantity of the sulphuric acid sufficien t to turn the colour pink. Add an 
excess of 5 mL of the acid.  Allow the solution to cool to room temperature. Add 100mL of ethyl 
eithe r, invert the separating funnel  while maintain ing the hold on the stopper, open t h e s t o p -core 
g r a d u a l l y , to release  a n y  pr e s s u r e  t h e n  c l o s e .  Gently s h a k e  t h e separator and 
again release the pressure. 
Transfer the aqueous  layer in another  separator and extract this solution with about  50mL of 
ethyl  ether. Separate the aqueous  layer from the ether layer and transfer the latter to the first 
separator containing the first ether layer. Repeat  the extraction an additional time. Wash the ether  
extracts with portions of about 50 mL of distilled water  until washings are neutral to methyl 
orange.  
Filter  the  ether  extracts  in  the  first  separator  through  a  dry  filter  paper  covered  with 
anhydrous sodium sulphate into a weighed  flask. Wash out the first separator and the filter with 
ethyl ether  and transfer the washin gs to the ether solution.  Distil off slowly the ether solution  
on a steam bath and to the residue add 5 mL of acetone. Warm the flask on the steam-bath 
for about one minute, remove it from the bath and then, while shaking the flask slowly at an 
angle of about  45˚ direct a current of dry air into its mouth for about one minute, thereby removing 
the bulk of acetone. Place the flask  in an oven  at a temperature of 90± 2˚ C for 10 minute s. 
Remove it from the oven  and blow with air as before for 15 seconds,  allow to cool in  the 
desiccator and reweigh.  Repeat the process of drying until  the difference  between two consecu tive 
weighi ngs is less than 0.005  g. 
NOTE 2: if the soap contains appreciable amounts of substances insoluble in water, the soap shall be extracted 
with 95 per cent  (v/v) ethanol before proceeding with this procedure. 
10.3.3 Calculation  
Total fatty matter, per cent by weight   =      A 
                × 100 
                                W 
Where, 
A = weight in g of the fatty matter, and  SZNS 006:2011  
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© SWASA 2011  – All rights reserved   7 
W = weight  in g of the material taken for the test. 
10.4 Determination of free alkali and free acid 
10.4.1 Reagents 
a) Pheno lphthalein Indicator  – prepared by dissolving  5 g of the indica tor in 500 mL ethanol , 
add 500 mL of distilled water with constant stirring. Filter if a precipit ate forms. 
b) Ethyl Alcohol  – Freshly boiled  and neutral to phen olphthalein, 95 per cent (v/v). 
10.4.2 Procedure 
Weigh 2 ± 0.01g to 10 ± 0.01g of the sample and digest  with 200 mL of freshly boiled ethyl 
alcohol  in a covered vessel on a steam-bath until the soap is dissolved.   Filter   into   a   filter   
flask   through   a   counte rpoised   filter   paper   neutral   to phenol phthalein, or  through a weighed  
Gooch or sintered crucible  of porocity 3 with suction, protecting  the solution from carbon dioxide  
and other  acid fumes during the ope ration by cove ring with a watch glass.  Wash the residue  on 
the filter several times with hot neutral ethyl  alcohol to remove all the alcohol soluble  matter. 
Heat the filtrate in alcohol  to boil and add 0.5 mL of 1% solution of phen olphthalein. Titrate with 
standard acid or alkali solution. 
Note 3: in the analysis of soaps known to contain little or no alkaline salts, it is unnecessary to filter the 
hot alcoho lic soap solution as described above. However the filtration should be carried out in all cases where 
alkaline salts such as silicates, phosphates, borates and similar salts are present, since these are known t affect 
the free alkali determination. Free alkali values in soap or surfactant mixtures containing borax are unreliable 
due to solubility of borax in hot alcohol. In this case see the test method for determination of borax, to 
determine the percentage of borax present, titrate an equivalent amount of borax with the standa rd acid, and 
subtract this  titer from the one obtained above  before calculating alkalinity as NaOH or KOH. 
10.4.3 Calculation 
Free alkali or acid per cent   =  V × M × F 
                                                          W 
Where, 
V = volume of acid or alkali solution  in millilitres 
M = molarity of acid or alkali solutio n; 
W = sample weight  in grams; and 
F = 4.7 for potassium oxide (K2O), 28.3 for oleic  acid, 3.1 for sodium oxide  (Na2O) with 4 
volumes of water. 
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10.5 Determination of number of fatty acids  
10.5.1 Reagents  
a) Sulphu ric acid – prepared by slowly mixing  1 volume of concentrated sulphuric acid 
b) Phenolphthalein  Indica tor 
c) Ethyl alcohol  (95%) – neutral 
10.5.2  Procedure 
Dissolve 50g  of the sample in 500mL hot water.  (If soaps to be tested contain  alcohol,  the 
alcohol  should be completely removed by evapo ration from the soap solutio n). Add 200mL of 
sulphuric acid,  heat gently until the fatty collects in a clear layer. Siphon  off the aqueous acid 
layer, add 300mL of hot water, boil gently for a few minutes, and siphon  off the aqueous  acid  
layer .  Repeat  the  washing  of  the  acids  in  this  manner  until  the  final washing  is neutral to 
methyl orange  indica tor (usual ly 3 to 6 washings). Complete this acidi fication and washing in a 
very short period of time, and keep the beaker cove red to prevent  oxidation of the acids.  After 
the last washing,  remove the last traces of water from the beaker with a pipette, filter the fatty 
acids  through one or two thicknesses of filter pape r, and dry at a temperature of 105 ˚C for 45 
to 60 min or heat rapidly to 130 ˚C and allow to cool.  
In a 250 mL Erlenmeyer flask dissolve  2g of the fatty acids,  accurately weighed  in 20 to 30 mL 
neutral ethyl alcohol (95%) near boiling point. Titrate with standard alkali, using phenol phthalein 
10.5.3    Calculation 
Calculate  the acid number of the fatty acid, expressed as milligrams of KOH per gram of fatty 
acid,  as follows 
Acid number = (AM × 56.1)/B 
Where, 
A = millilitres of KOH solution  required for titration  of the sample; 
M = Molarity of the KOH solution ; and 
B = grams of the sample used.  
10.6 Determination of rosin  
10.6.1 Principle  
Colophon ium (commercial rosins)  shall  only be conside red as rosin for the purpose of this 
standard. The mean equivalent  weight of the rosin acids is taken as 346. 
The method  described in this test gives results  approximately one per cent higher  than the  SZNS 006:2011  
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© SWASA 2011  – All rights reserved   9 
amount of rosin  actually  present .  Consequen tly, t h e percentage  of rosin  acids  actually  
present  is one less than the percentage  of rosin acids found  expe rimentally and hence  the minus 
one in the formula. 
10.6.2    Reagents 
a) Dilute  sulphu ric  acid  –  30  per  cent  (w/v)  obtained  by  cautious ly  adding  16 mL  of 
sulphu ric acid to 70 mL of water. 
b) Beta-napht halene  Sulphonic  Acid Solution  – (C10H7SO3H)  – obtained  by dissolving 
c) 40 g of the chemical in one litre of chemically pure, absolute  methyl alcohol. 
d) Standa rd Alcoho lic Potassium Hydroxide Solution  – Approximately 0.2 M in 95 per cent 
(v/v) ethyl alcohol,  accurately  standa rdized. Since alcohol  is volatil e, freque nt re 
standardization  is necessary. 
e) Phenolphthalein  Indica tor 
10.6.3    Procedure 
Weigh  50 ± 0.01g  of  the  sample  and  dissolve  in  500 mL  of  hot  water  until  complete ly 
dissolved.  Add 100 mL of the dilute  sulphuric acid to split the soap,  keep in steam-bath until the 
fatty matter separates in a clear layer. Siphon  off the lower aqueous  acid layer. Add 300 mL of 
hot water, boil gently for a few minutes, and siphon  off the aqueo us layer. Repeat the washing  
with hot water several times until the wash is free of mineral acids (or until the last washing  are 
neutral to methyl orange  indica tor). Complete the acidification and washing  in as short a period 
as possible,  keeping  the beaker covered to prevent  oxidation of the acids. Remove the last traces 
of water from the fatty acids through  one or two thickness of filter paper  and dry at 105 ± 2 ˚C 
for 45 minutes to 50 minutes, or heat rapidly  to 130 ˚C and allow to cool.  
Weigh accurately 2g of the mixture of fatty and rosin acids  into a esterification  flask and add 25 
mL of beta-naphthalene euphonic  acid solution. Boil gently under  a reflux condenser for 30 
minute s, adding  a few glass beads to ensure smooth boiling. Cool the conte nts of the flask and 
titrate immediate ly with standard alcoholic potassi um hydroxide  solution, using  0.5 mL of 
phenolphthalein indicator . The end point is reached  when the pink colour  persists for 30 
second s. Conduct  simultaneously a blank  determination with 25 mL of the esterifying agent  alone.  
10.6.4  Calculation 
The rosins  conte nt, per cent of total fats by weight = 34.6 (V1 – V2) M - 1 
   
                         W SZNS 006:2011  
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10   © SWASA 2011  – All rights reserved  
 
Where, 
V1   =  volume  in  mL  of  standa rd  alcoholic  potassium  hydroxide  solution  required  for  the 
material, 
V2 = volume in mL of standard alcoholic potassium hydroxide required for the blank,  
M = Molarity of alcoholic  potassium hydroxide,  
W = weight  in g of the material taken for the test (sample), and  the factor 34.6 applies  to 
colophoni um (commercial rosin ) since  the mean equiva lent weight  of the rosin is taken as 346. 
10.7 Determination of matter insoluble in water 
10.7.1    Principle 
The sample is extracted with ethanol,  filtered and the residue  extracted with hot water. 
10.7.2    Procedure 
Weigh 2 to 10 ± 0.01g  of the sample and digest with 200 mL of freshly  boiled ethyl alcohol in a 
cove red vessel  on a steam-bath until  the soap is completely dissolved .  Filter through  a filter 
paper  previous ly dried at 103 ± 2 ˚C for three hours and cool. Weigh the matter insolub le in 
water. 
10.7.3    Calculation 
Matter insolu ble in water per cent by weight =   100 (W2 – W1) 
    W 
Where, 
W1 = weight in g of the filter paper  
W2 = weight in g of the filter paper and the residue, 
W = weight of the material taken for the test  
 
10.8 Determination of matter insoluble in alcohol  
10.8.1  Reagents 
a) Phenolphthalein  Indica tor 
b) Ethyl alcohol  – freshly  boiled and neutral to phenolphthalein  
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© SWASA 2011  – All rights reserved   11 
10.8.2    Procedure 
Weigh accurately 2 to 10 ± 0.01 g of the sample and digest  with 200 mL of freshly boiled  ethyl 
alcohol  in a cove red vessel  on a steam-bath until the soap is completely dissolved.  Filter into a 
filter flask through a counterpoised filter  paper neutral to phenolpht halein , or through a  Gooch  
or sintered crucible of porocity 3 previously  dried at 103 ± 2 ˚C for three hours and cool. Weigh 
the matter insoluble in water. 
10.8.3    Calculation 
Matter insolu ble in water per cent by weight =      100 (w2 – w1) 
W 
Where, 
w2 = weight in g of the filter paper and the residue, 
w1 = weight in g of the filter paper, 
W = weight in g of the material taken for the test. 
10.9 Determination of chlorides 
10.9.1  Principle 
This  method  is  applicable  to  all  soaps  and  soap  products,  includi ng  those  containing 
synthetic  detergents.  Fatty acids  from an aqueous solution of soap are precipitated by the 
addition of calcium  nitrate  solution .  The  precipitate  is washed  free  of chlorides  and  the 
chlorides  in  the  washings  and  filtrates  estimated  by  titration  with  standard  silver  nitrate 
solution,  using  potassium chromate as indicator. 
10.9.2 Reagents  
a) Calcium  Nitrate Solution  – Neutral, chloride-free and containing 20 per cent (w/v) of 
calci um nitrate crystals [Ca (NO3)2.4H2O)] 
b) Dilute Nitric Acid – approximately 1 M 
c) Potassium  Chromate  Indicator – prepared by dissolving  5g of potassium chromate   
(K2CrCO4) in 100 mL of water. 
d)  Standa rd Silver Nitrate Solution – Approximately  0.1 M 
e) Methyl Orange  Indicat or – 0.04 per cent (w/v) solution.  
10.9.3    Procedure 
Weigh 10g ± 0.01g of the sample and disso lve in hot distilled water  in a 250 mL tall form SZNS 006:2011  
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12   © SWASA 2011  – All rights reserved  
beaker, add 20 mL of the calci um nitrate soluti on, mix thoroughl y, cool and filter into a 
one- mark 250 mL volumetric  f l a s k .  Wash the filter  free from  chlorides  u s i n g  
distilled  w a t er  allowing the washing to run into the flask. Shake the flask and the contents  
and dilute  to the mark. 
Take 100 mL of the solut ion, neutralize to the methyl orange  indicator  with dilute  nitric acid 
and titrate with silver  nitrate solution using  potassium chromate solution as the indicato r. 
Carry out a blank determination using  the same qualities  of the reagents but omitting the 
sample 
10.9.4    Calculation 
Chlorides (as sodium chloride), per cent by weight = 14.6  (V1 – V2) M 
  W 
Where, 
V1 = volume in mL of standard silver  nitrate solution required for the material, 
V2 = volume in mL of standard silver  nitrate solution required for the blank, 
M = Molarity of the standard silver  nitrate solution,  
W = weight in g of the material taken for the test. 
10.10     Determination of unsaponified and saponifiable matter 
10.10 .1 Principle  
The soap sample is disso lved in 50 per cent alcohol and extracted with petroleum ether. The ether  
extract  is  washed  free  from  soap  and  the  residue  obtained  after  evap orating  the solvent  is 
weighed.  This will contain  unsapon ified and unsaponi fiable  matter. To make a correction  for any 
fatty acids which may have  been  formed due to the hydrolysis of soap, the residue is dissolved in 
alcohol and titrated with  stand ard alkali  and acidity, calculated  as oleic  acid,  subtracted from the 
weight  of the residue. 
10.10 .2 Reagents  
a) Sodium  Bicarbona te – solid 
b) Ethyl Alcohol – 95 per cent, by volume 
c) Ethyl Alcohol – or redistilled  and diluted  with water to give 50 per cent, by vol ume, 
solution. 
d) Ethyl Alcohol – redistilled and diluted with water to give 10 per cent, by volume, solution.  SZNS 006:2011  
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© SWASA 2011  – All rights reserved   13 
e) Sodium  Hydroxide  Solution  – approximately 0.1 M. 
f) Standa rd Sodium  Hydroxide Solution  – 0.02 M. 
g) Petroleum  Ether – the solvent  shall  be of pentane type, with non-volatile evapo ration    
residue  of not more than 0.001 per cent (w/v). It shall have a distilling range  of between 
40˚C and 60˚C and s bromine number of less than one. 
10.10 .3 Apparatus  
a) Beaker  – 250 mL. 
b) Separating funnels  – 250 mL and 500 mL. 
c) Round  bottomed flasks  – 100mL and 250 mL. 
d) Microburette – 2 mL 
e) Pipette – 10 mL. 
f) Oven,  capable  of being controlled at 103 ± 2˚C. 
10.10 .4 Procedure  
Weigh  5  ±  0.2  g  of  the  sample;  place  it  in  a  250 mL  Erlenmeyer   flask  contain ing 
approximately 0.1 g of sodium  bicarbonate  and dissolve in 100 mL of 50 % ethyl alcohol.  
Warm and shake to effect solution, keeping  the temperature below  60 ˚C. Transfer or filter any 
un-dissolved  residue to a Gooch  crucible with a glass  wool pad or to a funnel using  a glass  
wool pad deposited on a perforated porcelain disc. Wash three times with hot 50 % ethyl  
alcoho l. Wash with small amounts of the petroleum ether to remove any traces of unsaponi fied and 
unsaponifiable  matter. Transfer the entire filtrate and washings  to a 500mL separating funnel , 
washing  with about 50 mL of 50 % ethyl alcohol  followed by two 10 mL portions  of 
petroleum ether. 
Add 50 mL of petroleum ether  and shake thoroughly and vigorously for one minute and allow 
settling  until both the layers are clear. If any emulsion occurs  break it with 10 g sodium 
sulphate.  The upper layer should  be about  40 mL, draw off completely the lower aqueous layer 
into anoth er separating funnel  of 500 mL capacity, using  a slender glass siphon. 
Repeat  the extraction at least six times, using 50 mL of petroleum ether each time. Wash the 
combined petroleum ether extracts first with a mixture of 15 mL of sodium hydroxide  solution of 
0.1 M and 15 mL of 95 % ethyl alcohol  and then at least thrice with 25 mL portions  of 10% 
ethyl  alcohol, shaking  vigorously each time until the wash water does not show  any pink 
colour  to phenolp hthalein.  Transfer the petroleum ether extract to a beaker and evapo rate the 
petroleum ether on a steam-bath with the help of a current of air. SZNS 006:2011  
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14   © SWASA 2011  – All rights reserved  
Test the residue for solubility by treating with 50 mL of petroleum ether at room temperature. 
Filter  the  insoluble  residue,  if  any,  and  collect  the  filtrate  washings  into  stared  flask. 
Evaporate and dry in the same manner on a steam-bath and finally, in air-oven  at 100˚C to 101 
˚C for 30 minutes. Weigh and return to the oven, reweighing at 15 minutes  intervals until 
constant weight  is reached. Take up the residue in 50 mL of 95% ethyl alcohol,  neutralise to 
phenol phthalein indica tor and titrate to the same colour  as that of the original neutral alcohol with 
0.02 M standard sodium hydroxide solution.  
Make a blank  test on the petroleum ether by evapo rating 250 mL of the ether with about 0.25 g of 
the stearin or some other hard fat previously brought  to constant weight  by heating and drying as 
in the actual determination. The blank  shou ld not exceed a few milligrams. Deduct the  value  for  
the  blank  on  petroleum   ether  from  the  weight  before  calculating   the unsaponi fied and 
unsaponifiable matter. 
10.10 .5 Calculation  
Calculate  the fatty acids as oleic acid (C18H34O2) equivalent of the 0.02 M standa rd sodium 
hydroxide  solution  used  in  the  titration  dedu ct  this  from  the  weight  of  the  residue  and 
express as percentage of the weight of the material taken for the test. 
Weight of the fatty acids  in the extract, as oleic acid = 0.282 × V × M 
Where, 
V = volume in mL of 0.02 M standa rd sodium hydroxide solution,  and 
M = Molarity of 0.02 M standard sodium hydroxide  solution.  
 
 
Unsaponified and unsaponifiable matter, per cent by weight = 100  (A-B) 
           W 
Where, 
A = weight  in g of the residue,  
B = weight  in g of the fatty acids,  and 
W = weight in g of the material taken for test. 
10.11   Determination of borax 
10.11 .1 Apparatus   SZNS 006:2011  
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© SWASA 2011  – All rights reserved   15 
a) Platinum Evaporating  Dish 
b) Round -bottomed Flask 
c) Water-cooled Reflux Condenser 
10.11 .2 Reagents  
a) Fusion  mixture – prepared by mixing  200g  of sodium carbonate with 15 g 0f powdered    
silica. 
b) Ethyl alcohol  – 95 % (v/v) 
c) Dilute Hydrochlo ric Acid – 1:1 (v/v). 
d) Calcium  Carbonate  – Solid, powder. 
e) Standa rd Sulphu ric Acid – approximately 1M. 
f) Methyl Orange  indicat or – Dissolve  0.1 g in 100 mL of water. 
g) Standa rd Sodium  Hydroxide Solution – Approximately 0.1 M, carbon dioxide free. 
h) Glyce rine – Neutral reagent. 
i) Phenolphtha lein Indica tor 
10.11 .3 Procedure  
Weigh 10±0.02g of the sample into a platinum evaporating  dish and add 2.15 g of fusion 
mixture and 15 mL of ethyl alcohol.   
Mix the contents with a glass rod and after washing  the rod with a little ethyl alcohol; 
evaporate the mixture to dryness on a water bath.  
Char the mixture thorough ly and ignite to fusion  over a burner.  
Cool, extract the residue  with boiling water into a round -bottom flask and acidify with 20 mL of 
dilute hydrochloric acid. An excess of the acid is neces sary if any phosphates are to be 
hydrolyzed.  Boil under reflux   for 2 hours, add a moderate excess of calcium carbonate and 
continue  boiling vigorously  for 20 minutes. Add a further small amount of calci um carbonate  
if the   precipitate is gelatinou s.  
Filter and wash  se ver al  t i me s  with  small  quantities  of water .   
Transfer  the  filtrate  and washings  into  a  round -bottom  flask,  and  neutralise  with  standa rd  
sulph uric  acid  in  the presence  of methyl orange indicato r. To the neutral solution , add 0.1 mL of 
standa rd sulphu ric acid, boil for 5 minutes more , cool the solution and neutralise it with 
standard solution of sodium  hydroxide .   SZNS 006:2011  
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16   © SWASA 2011  – All rights reserved  
Add  50  mL  of  glycerine  to  the  solution  and  titrate  it  with standard solution  of sodium 
hydroxide  in the presence of phenolphthalein  indicato r. After the end point  is reached, add 
anoth er 10 mL of glycerine and continue  the titration  until the pink colour  disappea rs again. 
Repeat  this until the addition of glycerine causes  no further change at the end point.  
10.11 .4 Calculation  
Borax (as Na2B4O710H2O) per cent by mass   =  9.536 V × M 
                                                                                                  W 
Where, 
V = volume in mL of standard sodium hydroxide  solution  required for the titration, 
M = Molarity of standa rd sodium hydroxide solution,  
W = mass in g of the material taken for the test. 
10.12  Determination of sulphates 
10.12 .1 Principle 
All organic  matter in the soap is thorough ly charred, the residue  digested with hydrochloric acid 
and extracted with hot water. The solution is filtered and the sulph ate determined in the filtrate 
gravimetrically as barium sulph ate. 
10.12 .2 Reagents 
a) Hydrochloric  acid – conce ntrated 
b) Barium Chloride Solution – 10 % (w/v), dissolve  100g of barium chloride (BaCl2.2H2O) 
in water and dilute  to 1 L. 
10.12 .3 Procedure 
Ignite and char the residue left after the removal of alcohol  solub le matter (see appendix  G) but 
for highest accuracy  result s, ignite  10 ± o.1g of the sample.  Digest  the ash from the ignition  
with 100 mL of water; add hydrochlo ric acid until neutral to methyl orange.  Add 10 mL excess 
HCL, filter and rinse residue thorough ly. 
Collect  the filtrates and the washings  after removal of any residue  if present, and make up to 
approximately 200 mL. Bring to boil the solution  and add 20 mL of BaCl2 solution  drop by 
drop using  a pipette.  Boil for two minutes  to coagulate the precipita te and allow to stand overnight  
and cool for 4 hour. Filter through a Gooch  crucible  or a sintered glass crucible, wash 
thorough ly with hot distilled  water and heat at 105˚C to 110˚C to constant weight 
NOTE 4: the addition of 5 mL of a saturated solution of picric acid after adding  10 mL of HCL accelerates the  SZNS 006:2011  
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© SWASA 2011  – All rights reserved   17 
precipitation of barium sulphate and reduces the standing  time from 4 hours to about 30 minutes. 
NOTE 5: excess of barium chlori de is necessary to reduce the solubility of barium sulpha te. Precipitation in 
hot solution by the ad dition of barium chloride in a slow steam, with stirring, minimizes mechanical occlution 
of barium chloride  and gives a course precipitate, which is less soluble in acids. 
10.12 .4 Calculation 
Sulphate s, as Na2SO4, per cent by mass =      60.86 A  
               ______  
W 
Where, 
A = mass in g of barium sulphate, and 
W = mass in g of the material taken for the test. 
 
10.13   Determination of moisture and volatile matter 
10.13 .1 Principle  
Two methods are employed;  
a) The oven method gives the moisture  and volatile content determined b y drying the material 
in an air-oven at a specified temperature. 
b) The  Distillation  method  –  this  method  gives  the  moisture  content  determined  by 
measuring the volume of water distilled over when boiled  under  reflux xylene - C6H4 
(CH3)2 , or toluene  – C6H5 (CH3) 
10.13 .2 Oven  method 
The oven  method is gene rally applicable  to all soaps, but for the following classes  of soaps, the 
distillation  method is to be preferred: 
a) Soaps containing  appreciable  amount of sodium silicate;  
b) Soaps obtained  from linseed oil and other oxidi zing oils which absorb oxygen and are    
likely  to  gain  weight  towards  the  end  of  the  test  if  the  oven  method  is  used. 
Nevertheless, if the oven method is used, the drying should be carried out either in an 
inert atmosphere or in a vacu um. 
c) Soaps contain ing an appreciable  amount of glycerol, especially those manufactures by 
the cod process or by thy semi-boiled  process, which usually give high results by the 
oven  method; and SZNS 006:2011  
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18   © SWASA 2011  – All rights reserved  
d) Soaps containing  sodium  hydrogen  carbonates,  perfume, ammonia, alcohol, carbolic acid 
and persalts. In ca se of dispu te, the moistu re content shall  be determined by distil lation  
method. 
10.13 .2.1 Apparatus 
a) Air – oven  
b) Petridish 
c) Weighing Balance  
d) Desiccator 
10.13 .2.2 Procedure 
Weigh 5±0.01g  of the soap in a petri dish of about  6 cm to 8 cm in diameter and about  2 cm to 4 
cm in depth and dry to constant weight in an air-oven  at a temperature of 105±2˚C. Cool in a 
desiccato rs and weigh.  Constant weight shall  be conside red to have been  attained  when successive 
heating  for one-hour periods  cooling  and weighing shows  a difference of not more than 0.1 % 
in the net loss in weight. 
10.13.2.3 Calculation  
Moisture and volatile  matter conte nt, % by weight = w 
              ___ 
               W 
            
Where, 
w = loss in weight in g of the soap upon  drying. 
W = weight in g of soap taken for the test. 
10.13 .3 Distillation  method 
10.13.3.1 Apparatus 
The appa ratus consis ts of a glass  flask heated by suitable  means and provided  with a reflux 
condenser  discha rging into a trap and connect ed to a flask. The connections between  the trap 
and the condens er and flask should  be interchangeab le ground -glass joints . The trap serves to 
collect  and measure the condensed  water and to return the solvent  to the flask. 
a)  Flask – a short-necked flask, of capacity  500 mL to 1000  mL made of hard resistan ce glass.  
b)  Condenser  – a water-cooled reflux-type glass  condenser  with an inner  tube diameter of 16 
mm to 17 mm and the inner  diameter of the jacket as 23 mm to 25 mm chosen according to  SZNS 006:2011  
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© SWASA 2011  – All rights reserved   19 
the expected amount of moisture content.  
c)   Receiver  – also known as the trap, provided with ground -glass  joint. The gradua tion scales 
on the receiver  shall  be numbered clearly with permanent lines of uniform thickness.  The  
capacity  corresponding  to  any  graduation  mark  is  defined  as  the volume of water at a 
temperature of 20˚C. 
d)  Heat source – the source of heat may be either  an oil-bath or electric heater provided with a 
sliding rheostat or other means of heat control. The temperature of the bath should  not be 
very much higher than the boiling point  of xylene or toluene  whichever solvent  is used. 
e)  Coppe r wire – long enough  to extend through the condenser with one end twisted into a 
spiral. The diameter of the spiral should  be such that it fits snugly  within the graduated  
portion of the receiver  and may be moved up and down. 
10.13 .3.2 Reagents 
a) Sodium Acetate – anhydrous 
b) Potassium dichromate -sulphu ric  acid cleaning  solution  – general grade 
c) Xylene  or Toluene  – saturate the xylene or toluene  by shaking with a small quantity of 
water and distil. Use the distillate  for the determination of moisture. 
10.13 .3.3 Procedure 
Clean the entire  apparatus  w i t h  potassium  d i c h r o m a t e -sulphu ric   acid cleaning  
s o l u t i o n . Rinse thoroughly with water and dry completely before use. Weigh accurately to 
0.01g; 10g to 50g of the sample,  place the material  in the 500 mL distillation  flask,  add, to 
the test portion, 100 mL to 300 mL of xylene or toluene and swirl to mix. Add a few porcelain 
pieces  to regulate  boiling  and  approximately  10  g  of  anhydrous  fused  sodium  acetate  to  
prevent violent  frothing.  Assemble the appa ratus and fill the receiver  with the solvent by pouring it 
through the conde nser until  it begins to overflow into the distillation flask .  
Insert a loose cotton plug in the top of the condenser to prevent condensation of atmosphe ric 
moisture  within the tube.  To ensure that the refluxing is under control, wrap the flask and the 
tube leading to the receiver with aluminum foil. Heat the flask so that so that the distillation  rate is 
about  200 mL drops per minute. When the greater part of the water has distilled over, increase the 
rate to about 200 mL drops per minute and continue  the distillation  until no more water is 
collected.  Purge the reflux condenser  occasiona lly during the distillation  wit 5 mL portions  of  
xylene  or  toluene  to  wash  down  any  moisture  adhe ring  to  the  walls  of  the condense r.  
Move  the  spiral  copper  wire  up  and  down  in  the  condenser  and  receiv er occasionally to 
help the water separate from the xylene or toluene,  thus causing  the water to settle at the bottom SZNS 006:2011  
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20   © SWASA 2011  – All rights reserved  of the receive r. Reflux until water-level  in the receiver  remains consta nt for 30 minute s; then 
shut off the source of heat. Allow to stand  for at least 15 minutes until the xylene or toluene  
layer is clear  with no emulsified zone; then read the volume of water at 20 ˚C. 
10.13 .3.4 Calculation 
The percentage, by mass of water and volatile matter in the soap is 
Moisture % = V × D × 100  
                                M 
Where, 
V = volume of water in millili tres at 20 ºC, 
D = density  of water at 20 ºC, 
M = the mass in g of the test portion 
10.13 .4 Test  reports 
The test report should  give the method used,  test conditions  and all details  required for complete 
ident ification of the sample. 
NOTE 6   Either procedure can be used, but b oth can be applied  when one serves as a data validation tool of the 
other. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
  SZNS 006:2011  
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© SWASA 2011  – All rights reserved   21 Bibliography 
 
 
KS 03-803: PART 1:1988,  Specifi cation for liquid soaps,  Part 1: Toilet soap 
KS 03-803: PART 2:1988,  Specifi cation for liquid soaps,  Part 2: Liquid  floor soap  
KS 09-42:197 7, Methods  of analysis for soaps  
SANS 238:2008,  Liquid  toilet soap  
SANS 20825 :1993, Environmentally acceptable  hand dishwashing  and light duty detergent 
(liquid) 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 SZNS 006:2011  
Edition 1  
22   © SWASA 2011  – All rights reserved   
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
ICS 71.100.40            
Price  based  on 21 pages .