TBS/CDC -2(5796) P3 
  
  
DRAFT TANZANIA STANDARD  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Mosquito repellent soap  – Specification  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
TANZANIA BUREAU OF STANDARDS  
  
 
  
© TBS  2020                                                                                                                            First Edition 20 20  
 Foreword  
 
This Draft Tanzania Standard is being  developed by the Soap and Detergents Technical Committee under 
supervision of the Chemicals Divisional Standards Committee and it is in accordance with the procedures of 
the Bureau.  
This is the first edition of the draft Tanzania standard for mosquito rep ellent soap. In reporting the results of 
analysis of a test if the final value is to be rounded off, it shall be done in accordance with TZS 4 Rounding off 
numerical values  
 
   
2 
  TBS/CDC -2(5796) P3 
 
Mosquito repellent soap  – Specification  
1 Scope  
1.1 This Draft Tanzania Standard specifies requirements, sampling and test methods for mosquito repellent 
soap for body cleaning and protection from mosquito bite s.  
1.2 This standard applies to mosquito repellent soap s containing N, N-diethyl -3-methylbenzamide  (DEET ) as 
the active ingredient supplied in the form of bars/cakes and produced from vegetable or animal oils or fats, 
fatty acids, or from a blend of all or part of these materials, with or without the addition of rosins or non-soapy 
surfactants . 
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 
docu ment (including any amendments) applies.  
TZS 638 (All parts)/ EAS 377 (all parts) , Cosmetics and cosmetics  
TZS 2102/ EAS 794, Determination of the microbial inhibition of cosmetic soap bars and liquid hand and body 
washes — Test method  
TZS 1780/ EAS 814, Determination of biodegradability of surfactants — Test method  
TZS 1396 -4/ISO 456, Surface active agents — Analysis of soaps — Determination of free caustic alkali  
TZS 1396 -6/ISO 685, Analysis of soap — Determination of alkali content and total fat ty matter content  
ISO 4315, Surface active agents -- Determination of alkalinity -- Titrimetric method  
ISO 862, Surface active agents — Vocabulary  
3 Terms and d efinitions  
For the purposes of this standard  the following  terms and definition s shall apply.  
3.1 Mosquito repellent soap  
product  in the form of a bar s or cake s containing mosquito repellent  agent (s) and soap of  fatty acids and /or 
synthetic surface active agents  
3.2 All terms and definitions given in ISO 862   
4 Requirements  
4.1 General  requirements  
4.1.1 The product  shall: 
a) be in the form of cakes or bars ; DRAFT TANZANIA STANDARD  TBS/CDC 2 (5796) P1  
 b) not be injurious to health when used in a manner and purpose meant for their use or under 
reasonably foreseen conditions ; 
c) not have an unpleasant odour ; 
d) be firm and smooth in texture ; and  
e) not contain any ingredients in amounts that are harmful to the human body and environment . 
4.2.2 The colour of the cake or bar shall generally be uniform . For the case of genuinely mottled products , 
the colour may not be uniform.  
4.2.3 Synthet ic surface active agent s, may be used and when used shall not be more than 4% by mass 
when tested in accordance with Annex D.  
4.2.4 All the ingre dients used in the  mosquito repellent soap  shall comply with the requirements of all parts 
of TZS 638  
4.3  Spec ific requirements  
Mosquito repellent soap  shall conform to the specific requirements given in Table 1 w hen tested in 
accordance with the methods prescribed therein.  
Table 1 — specific  requirements  
SL. No  Characteristic  Requirement  Test method  
i)  Total fatty matter, % by mass, min . 50 TZS 1396 -6 
ii)  Lather, mL, min . 200 Annex A  
iii)  Mush (loss in mass due mushing on a wet 
surface) , g/30 cm2, max .. 10 Annex B  
iv)  Freedom from grittiness  To pass the test  Annex C  
v)  Total alkalinity (as NaOH) % by mass, max . 1.0 TZS 1396 -6 
ISO 4315  
vi)  Free caustic alkali (as NaOH), % by mass, 
max. 0.05 TZS 1396 -4 
vii)  Rosins, as % of total fatty matter , max  2 Annex F  
viii)  Biodegradability  test To pass the test  EAS 814  
ix)  Mosquito repellent agents  (DEET - N, N -
diethyl -3-methylbenzamide, ) 10% – 30% Annex H 
 
5 Packaging and labelling  
5.1 Packaging  
Mosquito repellent soap  shall be wrapped as  to protect them from damage,  excessive loss or gain of moisture  
and to conserve the mosquito repellent agent co ntained.  
5.2  Labelling  
Each package shall be  legibly and indelibly labelled  with the information from  (a) to (i)  either in Englis h and/or  
Kiswahili or combination . Other language s may be added  as agreed between the manufacture r and supplier .  
a) name of the product as  ‘mosquito repellent soap ;  
4 
 b)  manufacturer’s name and physical address;  
NOTE  The name, physical address of the distributor/supplier and trade mark may be added as required.  
c) net content ; 
d) active ingredient s/mosquito repellent agent contained  with its level ; 
e) batch number or code number;  
f) date of manufacture and best before date;  and 
g) country of origin . 
h)  Precaution: not to be used to children under 12 years   
i)  Storage condition  
6 Sampl ing 
Sampling shall be done in accordance with Annex G.  
 
 
 TBS/CDC 2 (5796) P1  
 Annex A  
(normative)  
 
Test for lather volume  
A.1 General  
Strict attention shall be paid to all details of the procedure in order to ensure concordant results. Particular 
care should be taken to inve rt the cylinder exactly as described.  
A.2 Outline of the method  
A suspension of the material in standard hard water is taken in a graduated cylinder and given 12 inversions 
under prescribed conditions. The volume of the foam formed is observed after keepin g the cylinder for 5 min.  
A.3 Reagents  
A.3.1 Calcium chloride  CaCl 2.2H 2O, AR 
A.3.2 Magnesium sulphate  MgSO 4.7H 2O, AR 
A.3.3 Distilled water  
A.4 Apparatus  
A.4.1 Graduated cylinder  — Glass stoppered with graduation from 0 mL- 250 m L, with 2 -mL divisions. 
Overall height about 35 cm and the height of the graduated portion about 20 cm.  
A.4.2 100m L glass beaker  
A.4.3 Thermometer  of range 0 ºC– 110ºC 
A.5 Preparation of standard hard water  
Dissolve 0.220 g of calcium chloride  dehydrate  and 0.246 g of magnesium sulphate heptahydrate in distilled 
water. Dilute to 5 L with distilled water.  
NOTE  This standard hard water has a hardness of approximately 50 mg/kg calculated as calcium carbona te. 
A.6 Sample preparation  
Cut away the outer edges of mosquito repellent soap  using a knife.  
Using a stand up type of grater, grate up to 10 g – 15 g of the mosquito repellent soap  into small chips.  
A.7 Procedure  
A.7.1  Weigh 1 g of the grated chips accura tely in a 100 mL glass beaker. Add 10 m L of the standard hard 
water. Cover the beaker with a watch glass and allow to stand for 30 min. The operation is carried out to 
disperse the mosquito repellent soap .  
6 
 A.7.2  Stir the contents of the beaker with a glass rod a nd transfer the slurry to a 250 -mL graduated cylinder 
ensuring that not more than 2 m L foam is produced. Repeat the transfer of the residue left in the beaker with 
further portions of 20 m L of standard hard water ensuring that all the matter in the be aker is transferred to the 
cylinder.  
A.7.3 Adjust the contents in the cylinder to 100 m L by adding sufficient standard hard water. Bring the 
contents of the cylinder to 30 ºC. Stir the contents of the cylinder with a glass rod or thermometer to ensure a 
uniform suspension.  
A.7.4 As soon as the temperature of the co ntents of the cylinder reach 30 ºC, stopper the cylinder and give 
it 12 complete inversions, each inversion comprising movements in a vertical plane, upside down and vice 
versa. After the 12 inversions, let the cylinder stand for 5 min. Take the following readi ngs as shown in Figure 
A.1: 
a) foam plus water ( V1 mL). 
b) water only ( V2mL). 
 
Figure A.1 — Measurement of foam  
A.8 Calculation  
Lather volume = V1 - V2 
where  
TBS/CDC 2 (5796) P1  
  V1  Volume, in millilitres of foam + water;  
V2  Volume, in millilitresl of water only.   
8 
 Annex B 
(normative)  
Evaluation of the mushing properties of a mosquito repellent soap  
B.1 Principle  
A test piece of defined size is cut from the sample bar to remove harder outer layers. The test piece is 
preconditioned by giving 18 x 180 degree twists under running water at 25 °C or in a bowl of water at 25 °C. 
The bar is left for six hours on a piece o f fabric that has been wetted and drained of excess water.  During the 
six hours the soap/ cloth are covered to prevent drying.  At the end of the test period mush is removed from 
the test piece face in contact with the cloth. Weight loss from the test pie ce is expressed as mush per 30 cm2 
of original surface area in contact with the cloth.  
B.2 Equipment  
B.2.1  For sample preparation  
B.2.1.1  Coarse kitchen cheese grater  
B.2.1.2  Sharp thin blade knife or carpenters’  plane  
B.2.1.3  Callipers or ruler to ensure  the sample dimensions  
B.2.2   Other equipment/materials for the test  
B.2.2.1  Plastic or non -corrodible trays which are suitable sized for the test piece. Plastic soap dishes 7  cm x 
11 cm x 2 cm are quite suitable.  
B.2.2. 3 Cotton cloth pieces cut and folded to fit as a triple layer inside the trays. Normal, flat weave, cotton 
sheeting as used for bed sheets will be quite suitable.  
B.3  Bar preparation  
B.3.1 Three (3) individual bars of a type should be tested. A test piece is cut from each bar. The tes t piece 
should if possible,  have a working face (to be applied to the fabric) of (6 cm ±1 cm) x (4 cm ±1 cm).  
B.3.2  All bars in a set must be cut to have the same face size. If the smallest of the range of bars to be 
tested at a given time is too small to allow a working face within these limits, then all bars should be cut to the 
maximum size possible from the smallest bar.  
B.3.3  The longest axis of the test piece (6 cm ±1 cm) should be from a direction parallel to the longest axis 
of the original bar samp le. 
B.3.4  The working face should be a fresh surface from the interior of the bar sample. The face opposite the 
working face should be identified by making a small hole with a sharp object. This enables the working face to 
be identified after the precondit ioning step.  
B.3.5  To cut the bar it is convenient to first trim it to the approximate size using a coarse kitchen cheese 
grater and then to make the final adjustments to a smooth surface with a sharp thin -bladed knife or 
carpenters’  plane. If a plane is used, it is better to move the bar over the plane blade.  TBS/CDC 2 (5796) P1  
 B.4  Test procedure  
B.4.1 The tray plus triple thickness of cloth is filled with demineralised water. The tray is then held vertically 
to drain the water from the cloth. The ver tical position is maintained until water ceases to run from the dish in a 
continuous stream i.e. starts to drip.  
B.4.2 The area of the working face of the test piece is measured ( A). 
B.4.3 The working face of the bar is placed onto the damp fabric and then  the tray plus soap are covered 
e.g. with a sealed plastic bag, to prevent water loss.  
B.4.4 The covered test piece and holder are maintained at 25 oC for 6 h.  
B.4.5 The mushed bar test piece is remove d from the tray and is weighed (W1). 
B.4.6 Mush is removed from the working face of the bar test piece by scraping with the edge of a blunt 
sided spatula or plastic ruler.  
B.4.7 The test piece is reweighed ( W2) and the amount of mush removed is calculated as in B.5.  The mush 
is expressed as grams per 30cm2 of original test piece surface area.  
NOTE  The procedure for weighing the bar and removing the mush will take some minutes. During that time the 
remaining bars will continue to form mush. While this time is not critical for a set of three test pie ces from a given product, 
if more than one product is under test it is advised to stagger the start of the test for the second product. This will give 
adequate time to complete work on the first set before the 6 -hour storage time of the subsequent set is c ompleted.  
B.5 Calculation  
The mush of mosquito repellent soap  shall be expressed as follows : 
Weight of mush , W (grams)= W1 – W2 
Surface area of bar , A (square centimetres ) = (width x breadth)  
Mush =
AW30  grams per 30 cm2 
B.6 Criteria for conformity  
B.6.1  The test is done with three (3) separate samples of each product type, and the mean value fro m 
three samples is quoted ( X). The range of values ( R) is quoted as the difference between the highest and 
lowest values obtained for  a given product type.  
B.6.2  The sample lot of products shall be declared as conforming to the requirements for this standard if  
X + 0.6  x R is less than the maximum value given in Table 1.  
  
10 
 Annex C 
(normative)  
Determination of grittiness in a mosquito repellent soap  
C.1 Procedure  
C.1.1  Hold the mosquito repellent soap  under a smooth stream of running water at a temperature of 30 oC 
and gently rub the two sides of the bar on the palm of one hand for one minute ea ch side.  
C.1.2  Immerse the soap in a bowl containing 5 l of water at 30 oC and gently rub two opposite bar faces 
with the palm of one hand for 30 s (15 s  per bar face). Remove the bar from the water and continue to gently 
rub the two opposite bar faces for  a further 30 s (15 s  per face).  
C.1.3 Allow the used bar to dry in the open for 4 h and examine the surface.  A set of three  samples will be 
tested for each product.  
NOTE 1   Hands will become hydrated and insensitive with prolonged immersion in water. Test ers should wait 15 min 
between testing every three  sets of products ( nine grit tests) . 
NOTE 2   If using a bowl rather than running water use fresh water after testing every set of three  samples.  
C.2 Criteria for conformity  
The performance criteria are:  
a) during manipulation under running water , the mosquito repellent soap  shall not have a visibly rough 
surface and shall feel smooth to the touch ; and 
b) no gritty particles shall be observed on the surface of the dried bar 4 h after the washing test.  TBS/CDC 2 (5796) P1  
 Annex D  
(normative)  
 
Determination of active detergent content  
D.1 Outline of the method  
When equivalent amounts of cationic and anionic detergents are present in a two -phase mixture of water and 
chloroform, methylene blue will colour the two phases to the same de gree. Sodium alkyl benzene sulphonate 
and sodium lauryl sulphate or any other detergent can be titrated with a standard solution of cetyltrimethyl 
ammonium bromide.  
D.2 Reagents  
Weigh 1.5  g ± 0.001 g of cetyltrimethylammonium  ammonium bromide into a 250 -mL beaker. Add 100 mL of 
distilled water and stir until dissolved. Transfer quantitatively to a one-litre volumetric flask and make to 
volume. Mix thoroughly and standardize against solution B (see D.2.1). 
D.2.1 Anionic solution (Solution B)  
Weigh accurately such amount of standard alkyl sulphate of known combined SO 3 or active content so as to 
give exactly 0.320 g of combined SO 3into a 250 -mL beaker. Dissolve in 100 mL- 200 mL of warm water. 
Transfer quantitatively to one-litre volumetric flask and make to volume with water at roo m temperature. Mix 
thoroughly. This is the primary standard against which solution A, is standardized. Solution B is 0.004 N. 
D.2.2 Methylene blue indicator  
Dissolve 0.1 g of methylene blue in 100 mL of water. Transfer 30 mL of this solution to a one-litre flask. Add 
500 mL of water, 6.8 mL of concentrated sulphuric acid, 50 g of (NaH 2PO 4.H2O) sodium dihydrogen 
phosphate monohydrate and shake until dissolution is complete. Dilute to the mark.  
D.2.3 Chloro form  
Analytical reagent grade . 
D.3 Procedure  
D.3.1 Weigh accurately a sample of sufficient size to give approximately 0.320 g of combined SO 3 into a 
250-mL beaker. Sample size is crucial (see Note). Use 700 mL- 800 mL of warm water to transfer 
quantitative ly to a one-litre volumetric flask. Warm on steam bath and shake gently until the sample is 
dissolved and solution is clear. Cool, dilute to the mark and mix thoroughly.  
NOTE  The titration value V should be as near as to 10 mL as possible, say between 8 mL and 12 mL but never 
outside 5 mL and 15 mL. 
D.3.2 Pipette 10.0 mL of the sample solution into a 100 -mL glass stoppered cylinder (25 mmx 300 mm). 
Add 25.0  mL ± 0.5 mL of methylene blue solution and 10 mL ± 0.5 mL of chloroform (see Note). Titrate with 
solution A to the correct end point, shaking the cylinder carefully after such addition to avoid emulsion and 
maintaining temperature within prescribed limits of 20 C - 30 C by immersion in water bath, if necessary. As 
the end point is approached, the rate of transfer of colour increases and solution A shall be added dropwise 
with vigoro us shaking after each addition. If the approximate titration is known, 80 % of the required titrating 
solution should be added before shaking since this avoids emulsion forma tion. Application of vacuum to the 
titration cylinder may help to break some emulsions, if formed. The end point is reached when both layers 
have same colour intensity. The end point is very sharp and 0.05 mL will cause a distinct change in colour 
distribu tion at or near the equivalence point.   
12 
 NOTE  The titration value V should be as near to 10 mL as possible, say between 8 mL and 12 mL but never outside 
5 mL and 15 mL. 
D.3.3 Pipette 10.0 mL of the sample solution into a 100 -mL glass stoppered cylinder (25 m m x 300 mm). 
Add 25.0 mL ± 0.5 mL of chloroform (see Note). Titrate with solution A to the correct end point, shaking the 
cylinder carefully after such addition to avoid emulsion and maintaining temperature within prescribed limits of 
20ºC - 30ºC by immers ion in water bath if necessary. As the end point is approached, the rate of transfer of 
colour increases and solution A shall be added dropwise with vigorous shaking after each addition. If the 
approximate titration is known, 80 % of the required titrating  solution should be added before shaking since 
this avoids emulsion formation.  
Application of vacuum to the titration cylinder may help to break some emulsions, if formed. The end point is 
reached when both layers have same colour intensity. The end point is very sharp and 0.05 mL will cause a 
distinct change in colour distribution at or near equivalence point.  
NOTE  The volume of methylene blue solution and chloroform may be changed if found advantageous provided the 
same volumes are used in standardizing s olutions A and B.  
D.3.4 Calculation  
D.3.4.1  The percent combined SO 3 shall be expressed as follows:  
% combined SO 3  =   
where,  
V volume, in millilitres, of solution A used in the titration;  
N normality of solution A; and  
M mass, in grams, of the sample in the aliquot.  
D.3.4.2  The percent active detergent content shall be expressed as follows:  
Percent active detergent content = percent combined SO 3 x Mol ecular  weight of active detergent.  
NOTE  The molecular weight of active detergent should be suppl ied by the manufacturer on request.  
D.4 Alternative method  for determination of active detergent content  
(To be used only if the first method (Clause D.1) fails to work on the product).  
D.4.1 Field of application  
This method is applicable to the analysis of alkylbenzene sulphonates, alkyl sulphonate, sulphates and 
hydroxy -sulphates, alkylphenol and fatty alcohol ethoxysulphates and dialkyl sulphosuccinates and to the 
determination of active materials containing one  hydrophilic group per molecule.  
D.4.2 Principle  
Determination of anionic -active matter in a medium consisting of an aqueous and chloroform phase, by 
volumetric titration with a standard cationic -active solution (benzethonium chloride), in the presence of an 
indicator which consists of a mixture of a cationic dye (dimidium bromide) and an anionic dye (acid blue 1).  
D.4.3 Reagents  
D.4.3.1  The water used shall be of distilled quality.  
MNV 8.0 x   x TBS/CDC 2 (5796) P1  
 D.4.3.2  Chloroform , (specific  gravity = 1.48, distilling between 59.5ºC and 61.5ºC).  
D.4.3.3  Sulphuric acid , 2.5 M solution.  
D.4.3.4  Sulphuric acid , 0.5 M solution.  
D.4.3.5  Sodium hydroxide , 1.0 M standard volumetric solution.  
D.4.3.6  Sodium lauryl sulphate (sodium dodecyl sulphate)  (CH 3(CH 2)11OSO 3Na), 0.004 M standard 
volumetric solution. Check the purity of the sodium lauryl sulphate and simultaneously prepare the standard 
solution.  
D.4.3.6.1  Determination  of purity of  sodium lauryl sulphate — Weigh , 5 g ± 0.2 g of the product into a  250-
mL round bottom flask with ground glass neck. Add exactly 25 mL of the sulphuric acid solution ( D.4.3.4) and 
reflux into a water condenser.  
During the first 5 min - 10 min, the solution will thicken and tend to foam strongly; control this by removing the 
source of heat and swirling the contents of the flask.  
In order to avoid excessive foaming, instead of refluxing the solution may be left on a boiling water bath for 60 
min. 
After a further 10 min the solution clarifies and foaming ceases. Reflux for f urther 90 min. Remove the source 
of heat, cool the flask and carefully rinse the condenser with 30 mL of ethanol followed by water.  
Add a few drops of the phenolphthalein solution ( D.4.3.8) and titrate the solution with the sodium hydroxide 
solution ( D.4.3.5). 
Carry out a blank test by titrating 25 mL of the sulphuric acid solution ( D.4.3.4) with the sodium hydroxide 
solution ( D.4.3.5).  
The purity of the sodium lauryl sulphate, expressed as a percentage,  
 
where,  
V0 is the volume, in millilitres, of sodium hydroxide solution used for the blank test;  
V1 is the  volume, in millilitres, of sodium hydroxide solution used for the sample;  
M1 is the  mass, in grams, of the sodium lauryl sulphate to be checked; and  
M0 is the  exact molarity of t he sodium hydroxide solution.  
D.4.3.6.2  Weigh 0.004 M sodium lauryl sulphate standard volumetric solutions. Weigh, to the nearest 1 mg 
between 1.14 g and 1.16 g of sodium lauryl sulphate and dissolve in 200 mL of water. Transfer to a ground 
glass stoppered  1-L one -mark volumetric flask and dilute to the mark with water.  
Calculate the molarity, M 1, of the solution by means of the solution by means of the formula:  
 
where,  
m2 = mass in grams of sodium lauryl sulphate.  
D.4.3.7  Benzethonium chloride 0.004 M standard volumetric solution  
1O O 1   ) ( 28.84
MM VV−=  
100 x 288.4(%)  x   2
1purity m   M= 
14 
 Weigh, to the nearest 1 mg, between 1.75 g and 1.85 g benzethonium chloride and dissolve in water. Transfer 
to a ground glass -stoppered 1 -L one -mark volumetric flask and dilute to the mark with water.  
NOTE  In order to prepare a 0.004 M solution, dry the benzethonium chloride at 105 °C, weigh 1.792 g, to the nearest 
1 mg, dissolve in water and dilute to 1 L.  
D.4.3.8  Phenolphthalein, ethanolic soluti on containing 10 g/L. Dissolve 1 g of phenolphthalein in 100 mL 
of 95 % (v/v) ethanol.  
D.4.3.9  Mixed  indicator  
D.4.3.9.1  Stock solution  
Weigh 0.5 g ± 0.005 g dimidium bromide into a 50 -mL beaker, and 0.025 g ± 0.005 g of acid blue 1 into a 
second 50 -mL beaker.  
Add between 20 mL and 30 mL of hot 10 %. (v/v) ethanol to each beaker. Stir until dissolved and transfer the 
solutions to a 250 -mL one mark volumetric flask. Rinse the beakers into the volumetric flask w ith ethanol and 
dilute to the mark with 10 % (v/v) ethanol.  
D.4.3.9.2  Mixed  acid indicator solution  
Take 20 mL of the stock solution prepared above, put it in a 500 -mL one -mark volumetric flask. Add 200 mL of 
water, and 20 mL of 2.5 M sulphuric acid ( D.4.3.3) mix and dilute to the mark with water. Store away from 
direct sunlight.  
D.4.4 Apparatus  
Ordinary Laboratory apparatus, and  
a) bottles, 200 -mL, glass stoppered, or measuring cylinders, glass stoppered KNY cross check.  
b) burettes, 25 -mL and 50 -mL. 
c) one-mark volumetric flask, 1 -L capacity glass stoppered.  
d) one-mark pipette, 25 -mL. 
D.4.5 Procedure  
D.4.5.1   Standardization  of benzethonium chloride solution  
By means of the pipette transfer 25 mL of the 0.004 M sodium lauryl sulphate solution to a bottle or measuri ng 
cylinder, add 10 mL of water, 15 mL of the chloroform and 10 mL of the mixed indicator solution.  
Titrate with the 0.004 M benzethonium chloride solution. Stopper the bottle or measuring cylinder after each 
addition and shake well. The lower layer will b e coloured pink. Continue the titration with repeated vigorous 
shaking. As the end point approaches, the emulsions formed during shaking tend to break easily continue the 
titration drop by drop. Shaking after each addition of titrant, until the end point i s reached. This is at the 
moment when the pink colour is completely discharged from the chloroform layer, which becomes a faint 
greyish blue.  
The molarity, M, of the benzethonium chloride solution is given by the formula:  
 
where,  
2125 x   VM   M=TBS/CDC 2 (5796) P1  
 M1 is the molarity of the sodium lauryl sulphate solution; and  
V2 is the Volume, in, millilit res of benzethonium chloride added.  
D.4.5.2  Determination  
Weigh to the nearest 1 mg a sample of 30 g; dissolve the test portion in water. Add a few drops of the 
phenolphtha lein solution and neutralize to a faint pink colour with the sodium hydroxide solution or sulphuric 
acid solution as required.  
Transfer to one-litre volumetric flask and dilute to the mark with water. Mix thoroughly and, by means of the 
pipette transfer 25  mL of this solution to a bottle or measuring cylinder, add 10 mL of water,  and 15 mL of 
chloroform. Titrate with the benzethonium chloride solution as described in D.4.5.1.  
D.4.6 Expression of results  
The content as a percentage by mass, of anionic -active  matter  
 
=4V3M 
The amount of active matter, expressed in milli -equivalents per gram,  
 
where,  
M0 is the mass, in grams, of the test portion;  
M is the relative molar mass of anionic -active matter;  
M1 is the  molarity of the benzethonium  chloride solution;  
V3 is the  volume, in millilitres, of benzethonium chloride solution used for the titration of a 25 -mL aliquot 
of anionic -active matter solution.  
 
 
oo 3
 x 000  1 x 25100x  x 000  1  x  x  
MM M V=
o1 3 x  x 40
MM V=TBS/CDC -2(5413) P1  
 Annex F 
(normative)  
 
Determination of rosins  
F.1 General  
F.1.1  Colophonium (commercial rosins) only shall be considered as a rosin for the purpose of this 
standard. The mean equivalent weight of the rosin acid is taken as 346.  
F.1.2  The method described in this test gives resu lts approximately one per cent higher than the amount or 
rosin actually present. Consequently, the percentage of rosin acids actually present is one less than the 
percentage or rosin acids found experimentally and hence minus one in the formula.  
F.2 Reagen ts 
F.2.1  Dilute Sulphuric Acid — 30 %(w/v) obtained by cautiously adding 16 mL of sulphuric acid, specific 
gravity 1.84 to 70 mL of water.  
F.2.2.  Beta-naphthalene Sulphuric Acid Solution — C10H7SO 3H) — Obtained by dissolving 40 g of the 
chemical in one lit re of chemically pure, absolute methyl alcohol.  
F.2.3 Standard Alcoholic Potassium Hydroxide Solution — Approximately 0.2 N in 95 % (v/v) ethyl alcohol 
or in rectified spirit, accurately standardized. Since alcohol is volatile, frequent restandardization i s necessary.  
F.2.4 Phenolphthalein Indicator — Obtained by dissolving 1 g in 100 mL of 95 %(v/v) ethyl alcohol.  
F.3 Procedure  
F.3.1 Dissolve 10 g - 50 g of the sample in about 500 mL of hot water. Add 10 mL - 50 mL of the dilute 
sulphuric acid to split the  bar, keep in steam -bath until the fatty matter separates as a clear layer and siphon 
off the lower aqueous acid layer. Add 300 mL of hot water, boil gently for a few minutes and siphon off the 
aqueous layer.  Repeat the washing with hot water several time s until the wash liquor is free of mineral acids.  
Complete the acidification and washing in as a short 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 t wo 
thickness of filter paper and dry at 105 ºC ± 2 ºC for 45 min - 50 min.  
F.3.2  Weigh accurately 2 g of the mixture of fatty and rosin acids into an esterification flask and add 25 mL 
of beta -naphthalene sulphonic  acid solution.  Boil gently under a reflux condenser for 30 min, adding a few 
glass beads to ensure smooth boiling.  Cool the contents of the flask and titrate immediately with standard 
alcoholic potassium hydroxide solution, using 0.5 mL of phenolphthale in indicator.  The end point is reached 
when the pink colour persists for 30 s.  
F.3.3 Conduct simultaneously a blank determination with 25 mL of the etherifying agent alone.  
F.4 Calculation  
F.4.1  Rosin acids in fatty matter shall be expressed as follows : 
a) Rosin in fatty acids, percent by mass, uncorrected =  
where  
S is the volume in mL of standard alcoholic potassium hydroxide solution required for the material,  
B is the  volume in mL of standard alcoholic potassium hydroxide solution required for the  blank,  
()
MNBS−6.34TBS/CDC -2(5795) P1 
2 
 N is the normality of alcoholic potassium hydroxide, and 
M is the mass in g of the material taken for the test.  
The method described above gives results approximately one percent higher than the actual amount of rosin 
present.  As a result, the actual percentage of rosin acids present is one less than the percentage of rosin 
acids found experimentally.  
b) Rosin in fatty acids, percent by mass, corrected = Rosin in fatty acids, percent by mass, uncorrected – 
1.0. 
NOTE 1 — The mean equivalent mass of the rosin acids is taken as 346.  
NOTE 2 — When the quantity of rosin, expressed as percent by mass, is less than 5 in the bars, the results by this 
method are not so accurate as with bars containing higher rosin content. This method is also liable to give erroneous 
results with certain types of carbolic soaps containing high boiling tar acids and with other germicidal soaps, for example, 
soaps containing hexachlorophene.  
F.4.2 In all cases where the rosin content is found to be less than 5 percent, the actual presence or 
absence of rosin should be checked qualitatively by the Li ebermann -Storch test,  
 
F.4.2.1  Reagents  
 
a) Acetic a nhydride — pure.  
 
b) Dilute sul phuric acid — relative density 1 .53.  
 
F.4.2.2  Procedure  
 
Transfer 1 mL - 2 mL of the sample of fatty acids to a test -tube, treat with 5 mL - 10 mL of acetic anhydride 
and warm on a steam -bath. After cooling, pour 1 mL - 2 mL into a white porcelain dish and allow a drop or two 
of sulphuric acid to run down the side of the vessel. If rosin is present, a fugitive violet colouration changing to 
a brownish tinge is immediately produced at the margin of contact of the reagents. Che ck the test with a 
sample of fatty acids to which a small amount of rosin has been added.  
 
 TBS/CDC -2(5413) P1  
 Annex G 
(normative)  
 
Sampling  
G.1 Procedure  
G.1.1 In a single consignment, all packages (cartons) containing mosquito repellent soap s drawn from the 
same batch of production shall constitute a lot. For ascertaining the conformity of the lot to the requirements of 
this standard, tests shall be carried out on each lot separately. The number of packages to be selected for 
drawing the sample shall be in accordance with Table G.1. 
Table G.1 — Scale of sampling  
Number of packages (cartons) in 
the lot  
N Number of packages (cartons) to be 
selected  
n Number  of  samples  
4 to 15  3 3 
16 to 40  4 4 
41 to 65  5 2 
66 to 110  7 2 
111 and above  10 1 
 
G.1.2 The packages shall be selected at random, using tables of random numbers. If these are not 
available, the following procedure shall be applied:  
G.1.3 Starting from any package, count all the packages in one order as 1, 2, 3.... N, selecting every k 
thpack age, where k is the integral part of Nn.  
G.1.4 From each package thus selected, draw at random an equal number of cakes so as to obtain a total 
mass of at least 2 kg.  
G.2 Preparation of test samples  
G.2.1 Composite sample  
Weigh each cake separately (in cluding any material that may have adhered to the wrapper), and calculate the 
average mass. Cut each of the remaining cakes into eight parts by means of three cuts at right angles to each 
other through the middle. Grate finely the whole of two diagonally o pposite eighths of each specimen. Mix the 
gratings and place in a clean, dry, airtight glass container.  
G.2.2 Samples for testing  
Immediately after preparation of composite sample ( C.2.1), take at one time all test samples required for the 
tests in 4.2. W eigh out the test sample required for determination of free alkali or acid content, and use it 
immediately.  
 
 
 TBS/CDC -2(5795) P1 
4 
 Annex H 
(normative)  
Determination of DEET content  
 
H.1 General  
 
The sample is dissolved in carbon disulfide and the difference in absorbance at 14.18 μm and at 14.48 μm is 
determined. The quantity of meta -isomer is obtained from this value by means of a calibration curve prepared 
by the use of a reference standard.  
 
H.2 Apparatus  
H.2.1 Double -beam infrared spectrophotometer. Perkin -Elmer model 21 or equivalent.  
H.2.2 Two equivalent infrared absorption cells, with sodium chloride windows and a path length of 
approximately 0.4 mm.  
 
H.3 Preparation of calibration curve  
H.3.1 Weigh (to the nearest 0.1 mg) into four volumetric flasks sufficient amounts of the reference DEET 
standard of known purity to give concentrations of approximately 20, 40, 60 and 80 g/L when dissolved in 
carbon di sulfide.  
 
H.3.2 Fill the reference cell with carbon disulfide and the sample cell with each of the standard solutions in 
turn, and record the spectra. The spectrum may be scanned rapidly, except for the region 12 – 15 μm, where 
a normal speed should be us ed. Carry out a blank measurement with carbon disulfide to correct for any 
inequality in the paired cells and to determine whether a cell correction is required.  
 
H.3.3 Measure the absorbance at 14.18 μm and at 14.48 μm and calculate the difference betwee n these 
values, ΔA, for each of the solutions. Plot the values of ΔA against the concentration (g/L) of the meta -isomer.  
 
H.3.4 If a cell correction is required, the value of ΔA is determined from the formula:  
ΔA = [A 14.18 – A14.48]  ref. - [A14.48] blank  
 
Where , ref. = determination with reference standard  
blank = determination on CS 2 blank  
 
H.4 Procedure  
Weigh (to the nearest 0.1 mg)  about 0.5 g of the sample, transfer quantitatively to a 10 mL volumetric flask, 
and make up to the mark with carbon disulphide . Measure the infrared absorption at 14.18 μm and 14.48 μm 
using the same conditions as described in clause  H.3. Determine the con centration of meta -isomer by 
comparing this value with the calibration curve. A standard sample should be run each day to check the 
calibration of the instrument.  
 
H.5 Calculation  
DEET content (g/kg) =  𝐶1 × 𝑃
𝐶2 
 
where,  
C1 = concentration (g/L) of standard DEET found from calibration curve  
C2 = concentration (g/L) of sample taken  
P = purity (g/kg) of the reference standard