TBS/CDC -2(5415) P3 
 
© TBS 2018 — All rights reserved                                                                             First edition 2018   
DRAFT TANZANIA STANDARD  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
TBS/CDC -2(5415) P3- Baby toilet  soap  – Specification  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
TANZANIA BUREAU OF STANDARDS  
  
 
 
    
 
 
  TBS/CDC -2(5415) P3 
© TBS 2018 — All rights reserved                                                                             First edition 2018
  Foreword  
 
This Draft Tanzania Standard was developed by the Soap and Detergents Technical Committee 
under supervision of the Chemical s Division al Standards Committee and it is in accordance with the 
procedures of the Bureau.  
 
This Draft Tanzania Standard is the first edition.  
 
In the preparation of this Draft Tanzania Standard assistance was drawn from IS 10523:1983 , 
Specification for baby toilet soaps ; published  by the Indian Bureau of Standards . 
 
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  
  TBS/CDC -2(5415) P3 
 
© TBS 2018 — All rights reserved                                                                             First edition 2018  Introduction  
 
Normally the general requirements for baby  toilet soap are  similar to those prescribed for toilet soap 
meant for adults. However,  on account of natural  difference between a baby's skin and an adult's  skin 
due regard to toxicity and dermatological consideration is given during the manufacture of baby  toilet 
soap. This is because the skin of  babies, being much thinner and less cornified than that of an adult is 
highly susceptible to irritation and resistance to bacterial attack is not fully developed in the very 
young ones. If superficial layers of the  epidermis are damaged by any means, for example, by the use 
of harsh  toiletries, various skin disorders ma y develop. It is however not practicable to prescribe all 
such factors. It is, therefore, emphasized that manufacturers of baby toilet soap shall take the 
responsibility to establish and ensure dermatological safety of the soap.  
 
In order to achieve dermat ological safety of baby toilet soap the choice and selection of appropriate 
quality and quantity of different raw materials is very important.  
 
In this specification, unlike normal toilet soap, the use of rosin  has not been allowed because on 
account of it s unsaturated nature, its soap  may lead to irritation of the skin. On similar consideration a 
higher  limit for total fatty matter  (78%), low limits for free caustic alkali and free  carbonated alkali and 
low limits for heavy metals, namely, nickel, copper a nd iron have been prescribed.  
 
                                                                                     TBS/CDC -2 (5415) P3  
© TBS 2018 — All rights reserved                                                                             First edition 2018    
Baby toilet soaps — Specification  
 
 
1 Scope  
 
This Draft Tanzania  Standard specifies  requirements and methods of sampling and test for baby toilet 
soap.  
 
2 Normative references  
 
The following referenced documents are indispensable for the application of this document. The latest 
edition of the referenced document (including any amendments) applies.  
 
 
TZS 1396 -4/ISO 456, Surface active agents — Analysis of soaps — Determination of free caustic alkali  
 
TZS 1396 -8.2/ISO 457 , Soaps — Determination of chloride content — Titrimetric method  
 
TZS 1396 -2/ISO 672 , Soaps — Determination of moisture and volatile matter content — Oven method  
 
TZS 1396 -3/ISO 673, Soaps — Determination of content of ethanol -insoluble matter  
 
TZS 1396 -12/ISO 684, Analysis of soaps — Determination of total free alkali  
TZS 1396 -6/ISO 685, Analysis of soaps — Determination of total alkali content and total fatty matter 
content  
 
TZS 35, Soaps – Sampling and test methods  
 
TZS 59/ISO 3696 Water for analytical laboratory use – Specification and test method  
 
TZS 638/EAS 377(Part 1 - 5) Cosmetics and cosmetic  products  
 
3 Terms and d efinitions  
 
For the purpose of this standard the definitions given in TZS 35 shall apply . 
 
4 Requirements  
 
4.1 General requirements  
 
Baby toilet soap shall be a high grade, thoroughly saponified, milled soap or homogenized soap or both, 
white or coloured, mildly perfumed or unperfumed, and compressed in firm smooth cakes. It shall possess 
good cleaning and lathering properties. It shall  be free from rancidity.  It shall be free from toxic ingredients.  
 
4.2 Baby soap shall have no objectionable odour, shall have good lathering and cleansing properties  
and shall be free from grit when tested in accordance  with Annex A.  
 
4.3 Baby soap may contain chelating agents, colouring matter, medicaments, mild perfume and  
antioxidants which shall be non -injurious in use with soap.  
 
4.4 Baby soap shall not contain any rosin. 
 DRAFT TANZANIA STANDARD   
 
© TBS 2018 — All rights reserved                                                                             First edition 2018  4.5 Ingredients  
 
Baby toilet soaps may contain the following:  Colouring matter, perfume, preservatives and super fatting 
agents.  All other in gredients  exce pt moisture shall be declared on the label.  All these materials shall be 
non-injurious to skin  and shall comply  with TZS 638/EAS 377( Part 1 - 5) 
 
4.6 In addition to the above requirements, baby soap shall also comply with the requirements given in  
Table 1, when tested according to the corresponding test methods.  
 
Table 1 — Requirements for baby toilet soap  
 
S. No.  Characteristic  Requirements  Method of test  
(1) (2) (3) (4) 
i)  Total fatty matter, percent by mass, min  78.0 TZS 35  
ii)  Moisture and volatile matter (at 105  °C), 
percent by mass , max  15.0 TZS 35  
iii)  Matter insoluble in alcohol , percent by mass, 
max  0.2  TZS 1396 -3/ISO 
673 
iv)  Matter insoluble in water, percent by mass , 
max  0.5 TZS 35  
v)  Free caustic alkali, as sodium hydroxide 
(NaOH), percent by mass, max 0.03 TZS 1396 -4/ISO 
456 
vi)  Chlorides, as  sodium chloride (NaCI), percent 
by mass, max 1.0 TZS 1396 -8.2/ISO 
457 
vii)  Free carbonated alkali, percent by mass, max  0.5 TZS 1396 -12/ISO 
684 
viii)  Free f rom grit  To pass the test  Annex A 
ix)  Nickel content  Not detected  Annex B 
x)  Iron content, mg/kg , Max  10 Annex C 
xi)  Copper (as Cu) contents, mg/kg , max  3 Annex D 
xii)  Free f rom rosin  To pass the test  Annexes E and F  
Note:  
Calculation of results  
 
Baby toilet soap is liable to lose moisture on keeping. The results of analysis in respect of other 
characteristics shall be recalculated in relation to the minimum specified total fatty matter by means of the 
equations:  
 
matterfatty  total Actualmatterfatty  total specified Minimum result  Actual result ed Recalculat  
 
 
Where the minimum specified total fatty matter = 78.0 %.  
 
 
 
 
                                                                                     TBS/CDC -2 (5415) P3  
© TBS 2018 — All rights reserved                                                                             First edition 2018    
 
 
5 Packing and labelling  
 
5.1 Packing  
 
The material shall be packed as agreed between the  purchaser and the supplier.  
 
5.2 Labelling  
 
5.2.1  The packages shall be securely closed, legibly and indelibly labelled in Kiswahili and /or English, 
and any other language as agreed between the manufacturer and supplier with the following information:  
 
 
a) name of the product ; 
 
b) manufacturer's name and address and/or his recognized trade -mark, if any;  
 
c) net mass when packed;  
 
 
d) batch No. or Lot No. in code or otherwise;  
 
e) manufacture and expiry dates.  
 
 
f) The words ‘baby soap’  
 
g) Country of origin  
 
 
6 Sampling  
 
6.1 For this purpose, sampling and preparation of test samples  shall be as prescribed in TZS 35  
 
6.3 Criteria for conformity  
 
For each of the characteristics which has been determined on the samples the mean (
x ) and the range 
(R) of the test results shall be calculated as follows:  
 
results test of Numberresults test the of sum The   )x( Mean
 
 
results test the of values minimum the and maximum the between difference The  (R) Range 
 
 
The lot/batch  shall be deemed as conforming to the requirements given in Table 1  express ed as  (
x - 
0.6R) is greater than or equal to minimum value given in Table 1, and (
x  + 0.6 R) is less than or equal the 
maximum value given in Table 1.  
 
7 Tests  
 
7.1 Tests shall be conducted in accordance with the standards listed in Clause 2  and A nnexes  A, B, C 
and D.  
 
7.2 Quality of reagents  
 
Unless specified otherwise, pure chemicals and distilled water (TZS 59)  shall be employed in the tests.  
 
NOTE  'Pure chemicals' shall mean chemicals that do not contain impurities which affect the results of analysis.   
 
© TBS 2018 — All rights reserved                                                                             First edition 2018                                                                                        TBS/CDC -2 (5415) P3  
© TBS 2018 — All rights reserved                                                                             First edition 2018   Annex A  
(normative)  
 
Test for “free from grit ” 
 
 
A.1 Outline of the method  
 
Soap is rubbed with water between the hands for a specified  time and examined for its gritty or rough feel, 
if any.  
 
A.2 Procedure  
 
A.2.1 Hold a bar of soap in running tap water and rub between both  hands for about 3 min. No gritty or 
rough feel should be perceived  while rubbing the soap surface. Examine the surface of the bar which  shall 
not be rough and shall feel smooth when the fingers are moved  across the surface.  
A.2.2 Set the bar on and let it dry for 24 h at  room  temperature and examine its surface. The soap shall 
be taken to have passed the test if there is no  gritty or rough feel on the surface.  
   
 
© TBS 2018 — All rights reserved                                                                             First edition 2018  Annex B 
(normative)  
 
Determination of nickel  
 
 
B.0 Outline of the method  
 
The method is based on the isolation of metal from the soap and  reaction between nickel in the oxidized 
form with dimethyl glyoxime  forming a red colour.  
 
B.1 Reagents  
 
B.1.1 Sodium hydroxide — AR grade.  
 
B.1.2 Concentrated hydrochloric acid — Conforming to  relevant standard . 
 
B.1.3 Dimethyl glyoxime solution — 0.1 percent ( v/v) in 95 percent ethyl alcohol.  
 
B.1.4 Saturated bromine water 
 
B.1.5 Liquor ammonia — Relative density 0.9.  
 
B.2 Procedure  
 
B.2.1 Isolation of metals from soap 
 
Weigh 50 g of soap in a  beaker and dissolve in hot water. Add to this soap solution 40 mL of concentrated 
hydrochloric acid, stir and keep on steam bath until fatty  acid layer separates. Add 20 g of paraffin wax, stir 
at intervals and  allow it to settle until phases are clear. Co ol to room temperature.  
 
B.2.1.1  Remove wax cake with rod, rinse with water and add rinsing  to aqueous phase. Evaporate, 
aqueous phase to about 60 mL by gentle  boiling. Add 100 mL of water and filter through paper washed  
previously with hydrochloric acid. Evaporate filtrate and washings to  about 60 mL. Cool and transfer to 
volumetric flask. Make up the  volume to 100 mL. Take aliquot portions for metal estimation.  
 
B.2.2 Determination of nickel content  
 
Take 50 mL aliquot of the  aqueous solution from the tes t solution in a 250  mL beaker. Evaporate  the 
solution to about 15 mL by heating. Transfer the solution to a 50  mL glass stoppered volumetric flask using 
a small quantity of water for  rinsing the solution from the beaker into the volumetric flask. Add to the flask 3 
mL of saturated bromine water and allow to stand for one minute.  Add liquor ammonia dropwise until 
excess bromine is destroyed as  indicated by the disappearance of brown colour. Then add 5 mL of liquor  
ammonia in excess. If a precipitation occu rs, filter the solution and wash  the precipitate with distilled water; 
combine the filtrate and the  washings and concentrate to a volume of a few millilitres and transfer  to a 50  
mL volumetric flask. Add 10 mL of dimethyl  glyoxime solution,  followed by 15 -20 mL of 95 percent ethyl 
alcohol. Mix thoroughly and  make up the volume and again mix thoroughly. Allow the solution to  stand for 5 
minutes to permit full development of colour. The sample  shall be considered to have passed the test if no 
pink colour deve lops.  
                                                                                      TBS/CDC -2 (5415) P3  
© TBS 2018 — All rights reserved                                                                             First edition 2018   Annex C 
(normative)  
 
Determination of iron  
 
C.0 Outline of the method  
 
The method is based on the isolation of metal from the soap by  dissolving in hot water. The aqueous 
extract is treated with citric acid  to sequester aluminium and then thioglycolic acid in ammoniacal  solution 
is added and colour measured spectrophotometrically.  
 
C.1 Apparatus  
 
C.1.1  Spectrophotometer  
 
C.2 Reagents  
 
C.2.1  Liquor Ammonia  — Relative density 0.9.  
 
C.2.2  Sulfuric acid — 50 percent (v/v). 
 
C.2.3  Citric acid (aqueous solution)  — 50 percent ( v/v). 
 
C.2.4  Thioglycolic acid (aqueous solution)  
 
C.2.5  Standard iron solution  — Containing 10 µg of iron per mL prepared from ferric ammonium 
sulphate [Fe 2(SO 4)3.(NH 4)2SO 4.12H 2O] in acid solution.  
 
C.2.6  Methyl red indicator  — 0.1 percent aqueous solution.  
C.2.7 concentrated hydrochloric acid  
C.2.8 paraffin wax   
 
C.3 Procedure  
 
C.3.1  Isolation of metals from soap 
 
Weigh 50 g of the soap  sample in a beaker and dissolve it with hot water. To this soap solution  add 40 mL 
of concentrated hydrochloric acid with constant stirring and  keep the beaker on steam bath until fatty acid 
layer separates. Add  20 g of paraffin wax to this solution while hot. Stir the solution at  intervals and allow it 
to settle until phases are clear.  Cool the mass to  room temperature. Remove the wax cake with rod, rinse 
with water  and add the rinsing  to aqueous phase. Evaporate the aqueous phase  to above 60 mL by gentle 
boiling. Add 100 mL of water and filter  through paper washed previously with hydrochloric acid. Evaporate  
the filtrate and washings to about 60 mL. Cool and transfer the  solution to a volumetric flask and make up 
the volume to 100 mL. Take  aliquot portion of the solution for metal estimation.  
 
C.3.2  Determination of iron 
 
Take 5 mL aliquot of the aqueous  solution from the test solution in a 25  mL volumetric flask. To this add  4 
mL citric acid solution and 0.02 mL methyl red indicator and liquor  ammonia till the colour of the solution 
turns yellow. Then add 3 mL liquor ammonia in exc ess. Cool the solution and add 3 mL thioglycolic  acid. 
Make up the volume to 25 mL and mix the solution thoroughly.  Filter the solution through acid washed and 
dried filter paper. Measure  absorbance of the clear solution at 540 nm in the spectrophotometer  using 
water as reference. Prepare a calibration curve with standard  iron solution and determine the iron content 
of the soap sample from it.  
 
   
 
© TBS 2018 — All rights reserved                                                                             First edition 2018  Annex D 
(normative)  
 
Determination of copper  
 
 
D.0 Outline of the method  
 
The method is based on the isolation of metal from the soap and  to make a copper complex using zinc 
dibenzyl dithiocarbamate in  carbon tetrachloride solution and measure the colour of the solution  
spectrophotometrically.  
 
D.1 Apparatus  
 
D.1.1  Spectrophotometer  
 
D.2 Reagent s 
 
D.2.1  Zinc dibenzyl dithiocarbamate solution  — 0.05 percent in  (v/v) in carbon tetrachloride.  
 
D.2.2  Standard copper solution  — Containing 1 pg of copper per  mL (prepared from a stock solution of 
100 times the concentration).  
concentrated hydrochloric acid  
paraffin wa x 
sulphuric acid  
 
D.3 Procedure  
 
D.3.1  Isolation of metal from soap 
 
Weigh 50 g of soap sample in  a beaker and dissolve it with hot water. To this soap solution add  40 mL of 
concentrated hydrochloric acid with constant stirring and  keep the beaker on steam  bath until fatty acid 
layer separates. Add  20 g of paraffin wax to this solution while hot. Stir the solution at  intervals and allow it 
to settle until phases are clear. Cool the mass to  room temperature. Remove the wax cake with rod, rinse 
with water  and add the rinsing  to aqueous phase. Evaporate the aqueous phase  to about 60 mL by gentle 
boiling. Add 100 mL of water and filter  through filter paper washed previously with hydrochloric acid.  
Evaporate the filtrate and washings to about 60 mL. Cool and tran sfer the solution to a volumetric flask and 
made up the volume to 100 mL. Take aliquot portion of the solution for metal estimation.  
 
D.3.2  Determination of copper  
 
Take 20 mL aliquot of the aqueous solution and to it add 10 mL of zinc dibenzyl  dithiocarbamate solution 
followed by 25 mL sulphuric acid in a separating funnel. Shake the solution for one minute and allow it to 
settle. Run the lower carbon tetrachloride layer in to a 25 mL volumetric flask. Wash the aqueous layer with 
carbon tetrach loride and transfer through glass wool  to volumetric flask. Make up the volume and mix well. 
Measure absorption of the clear solution at 435 nm in the spectrophotometer. Prepare a calibration curve 
with standard copper solution and determine the copper con tent of the soap sample from the curve.  
 
NOTE  The standard solution shall also be extracted with carbon tetrachloride before estimation of colour.  
                                                                                      TBS/CDC -2 (5415) P3  
© TBS 2018 — All rights reserved                                                                             First edition 2018   Annex E 
(normative)  
 
Identification of  rosin content of fatty mater in soaps  
 
E.1 Scope  
 
This Annex  specifies the Halphen -Grimaldi and Liebermann -Storch method for the identification of rosin in 
fatty matter.  
 
E.2 Reagents  
 
NOTE  Use only analytical grade reagents and distilled water.  
 
E.2.1 Acetic anhydride.  
 
E.2.2 Sulphuric acid, density 1 .53 g/ mL (Cautiously add 97 mL of sulphuric acid “density  1.84 g/ mL” to 
100 mL of water ). 
 
E.2.3 Solution A. Dissolve 10 g of phenol in 27 mL of chloroform.  
 
E.2.4 Solution B. Dissolve 10 mL of bromine in 40 mL of chloroform.  
 
E.3 Procedure  
 
E.3.1 Halphen -Grimaldi method  
 
E.3.1.1 Place one or two drops of the fatty matter, reserved from the determination of fatty matter  (ISO 
685), in a porcelain basin and add approximately 2 mL of the solution A to dissolve it. Wet  the walls of the 
basin by tilting and turning it and let it stand for a few seconds so that the walls of  the basin are covered 
with a very thin film of the solution.  
 
E.3.1.2 Hold the neck of the flask containing the solution B in such a position that the bromine  vapour 
diffuses into the porcelain dish a nd comes into contact with the walls. In the presence of  rosin a blueish -
grey to purple colour develops immediately.  
 
E.3.1.3 Carry out a comparison test with a sample of fatty matter to which 2 % ( m/m) of rosin has  been 
added.  
 
NOTE  Should the colour reac tion in A.3.1.2 be masked by other colours, conduct a second qualitative test, using the Liebermann -
Storch method.  
 
E.3.2 Liebermann -Storch method  
 
E.3.2.1 Place 1 g - 2 g of the fatty matter in a test tube, add 5 mL - 10 mL of the acetic anhydride,  and heat 
the mixture in a boiling water bath for approximately 3 min. Cool to room temperature and  pour 1 mL - 2 
mL of the solution into a white porcelain basin.  
 
E.3.2.2 Allow one or two drops of the sulphuric acid to run down the side of the basin. If rosin is present, a 
violet colour immediately develops where the acid is in contact with the solution. This  colour then turns 
brown on standing.  
 
E.3.2.3 Carry out a comparison test with a sample of fatty matter to which 2 % ( m/m) of rosin has  been 
added.  
 
   
 
© TBS 2018 — All rights reserved                                                                             First edition 2018  Annex F 
(normative)  
 
Determination of rosin content of fatty mater in soaps  
 
F.1 Scope  
 
This Annex  specifies a method for the determination of the rosin content of fatty matter in soaps.  
 
NOTE 1  Before proceeding with the quantitative determination of rosin, first establish its presence by a qualitative test (see Annex  
E). 
 
NOTE 2  The following method is not accurate for rosin concentrations below a mass fraction of 5 %.  
 
F.2 Reagents  
 
NOTE  Use on ly analytical grade reagents and distilled water.  
 
F.2.1 Diethyl ether  (Free from peroxides ) 
 
. 
 
F.2.2 Sodium chloride  
 
F.2.3 Anhydrous  Sodium sulfate  
 
 
 
F.2.4 Hydrochloric acid solution  
 
Dilute one volume of concentrated hydrochloric acid (density 1 .16 g/ mL) with two volumes of  distilled 
water.  
 
F.2.5 Sodium hydroxide solution  
 
10 % mass fraction aqueous solution.  
 
F.2.6 Naphthalene -2-sulfonic acid solution  
 
Dissolve 40 g of naphthalene -2-sulfonic acid in 1 L of absolute methanol.  
 
F.2.7 Sodium chloride solution, saturated  
 
Shake an excess of sodium chloride with water at ambient temperature until no more dissolves.  Keep the 
solution over solid sodium chloride.  
 
F.2.8 Sodium chloride solution, 10 %  
 
Dissolve 10 g of sodium chloride in 100 mL of water.  
 
F.2.9 Standard ethanolic potassium hydroxide solution, 0 .2 N 
 
F.2.9.1 Preparation  
 
Purify 95 % (by volume fraction) ethanol by boiling 1 .5 L of it over 20 g of potassium hydroxide for  1 h 
under reflux. Distil, discarding the first 50 mL of the distillate and stopping the distillation when  
approximately 1 .3 L have been distilled. Dissolve 12 g of potassium hydroxide in 1 L of the purified  ethanol, 
allow the solution to stand for approximately one week, and then decant the clear  supernatan t liquid from 
any potassium carbonate that has precipitated.  
                                                                                     TBS/CDC -2 (5415) P3  
© TBS 2018 — All rights reserved                                                                             First edition 2018   F.2.9.2 Standardization  
 
Accurately weigh out approximately 1 g of potassium hydrogen phthalate (previously dried at  110 °C ± 5 °C 
for 3 h) into a 250 mL Erlenmeyer flask. Add approximately 100 mL of carbon  dioxide -free distilled water 
and three drops to five drops of the phenolphthalein indicator, and swirl  gently until the solid has dissolved. 
Titrate the solution with the standard ethanolic potassium  hydroxide solution, until a permanent pink colour 
is formed.  
 
F.2.9.3 Calculation  
 
Normality of the standard ethanolic potassium hydroxide solution ( N): 
 
B. AN8974
 
 
where  
 
A is the mass of the potassium hydrogen phthalate, in grams;  
 
B is the volume of the standard ethanolic potassium hydroxide solution used for the  titration, 
in millilitres.  
 
F.2.10 Methyl orange indicator  
 
Dissolve 0 .2 g of methyl orange in 100 mL of carbon dioxide -free water.  
 
F.2.11 Phenolphthalein indicator  
 
Dissolve 0 .5 g of phenolphthalein in 100 mL of freshly boiled, 95 % (by volume fraction) ethanol.  
 
F.3 Procedure  
 
F.3.1 Preparation of fatty matter  
 
F.3.1.1 Carbolic soaps  
 
F.3.1.1.1  Weigh out accurately into a 600 mL beaker such quantity of the test sample as contains  
approximately 40 g of fatty matter and dissolve it in approximately 400 mL of hot water, to which  40 mL of 
the sodium hydroxide solution has been added.  
 
F.3.1.1.2  Salt out the soap by adding sufficient sodium chloride to the hot solution to saturate it (at ambient 
temperature) with sodium chloride. Filter the soap quantitatively, and allow it to drain.  
 
F.3.1.1.3  Dissolve the drained soap in approximately 400 mL of hot water, and repeat the salting out  and 
filtering procedure.  
 
F.3.1.1.4  Wash the soap th oroughly with the saturated sodium chloride solution, and proceed in  
accordance with F.3.1.2.2 to F.3.1.2.7.  
 
F.3.1.1.5 Reserve the combined filtrates and washings for the determination of carbolic acids.  
 
F.3.1.2 Other soaps  
 
F.3.1.2.1  Weigh accurately in to a 600 mL beaker such quantity of the test sample as contains  
approximately 40 g of fatty matter.  
 
F.3.1.2.2  Dissolve the soap in approximately 400 mL of hot distilled water, cool the solution, and  slowly add 
an excess of the hydrochloric acid solution. Cover the beaker with a watch -glass and  heat the contents 
until the fatty matter separates into a clear layer, but do not allow the temperature  to exceed 60 °C.  
  
 
© TBS 2018 — All rights reserved                                                                             First edition 2018  F.3.1.2.3  In the cases of liquid and gel soaps, acidify the soap as it is.  
 
F.3.1.2.4  Cool to approximately 25 °C and transfer the contents of the beaker to a separating funnel.  Rinse 
the watch -glass and the beaker with portions of the diethyl ether totalling 100 mL and add  them to the 
separating funnel. Shake the mixture in the separating funnel v igorously for 1 min, and  let it stand until the 
two phases have separated.  
 
F.3.1.2.5  Draw off and discard the aqueous layer and wash the ether extract with 50 mL portions of  the 
sodium chloride solution until the last washing is neutral to the methyl oran ge indicator.  
 
F.3.1.2.6  Filter the washed ether extract into a 250 mL beaker through a filter paper containing  
approximately 5 g of anhydrous sodium sulfate, and wash the separating funnel and the filter with  small 
portions of the diethyl ether.  
 
F.3.1.2.7  Evaporate the ether extract plus washings on a warm water bath. When the residue is just  dry, 
heat it rapidly to 130 °C and immediately place the beaker in a desiccator to cool.  
 
NOTE  F.3.1.2.2 to F.3.1.2.7 should be completed in the shortest possible period of time, so as to prevent oxidation of the fatty 
acids.  
 
F.3.2 Determination of rosin content  
 
F.3.2.1 Weigh accurately into a 150 mL flask with a ground -glass joint approximately 2 g of the  prepared 
fatty matter ( F.3.1.2.7) and reserve the  rest in the case of soap powders for the fatty matter  titre 
determination.  
 
F.3.2.2 Add exactly 25 mL of the naphthalene -2-sulfonic acid solution to the flask and two or three  glass 
beads, and boil under reflux for 30 min.  
 
F.3.2.3 Carry out a blank test at the same time, using exactly 25 mL of the naphthalene -2-sulfonic  acid 
solution only.  
 
F.3.2.4 Cool the contents of both flasks (sample and blank) to ambient temperature, add 0 .5 mL of the 
phenolphthalein indicator to each flask, a nd immediately titrate to the end point with the  standard ethanolic 
potassium hydroxide solution.  
 
F.4 Calculation  
 
Rosin content of fatty matter, as a mass fraction percentage ( R): 
 
01634.C. N)BA(R 
 
 
where  
A is the volume of the standard ethanolic potassium hydroxide solution used for the titration  
of the sample solution, in millilitres;  
 
B is the volume of the standard ethanolic potassium hydroxide solution used for the titration  
of the blank solution, in millilitres;  
 
N is the normality of the sta ndard ethanolic potassium hydroxide solution;  
 
C is the mass of the fatty matter taken, in grams.  
 
                                                                                      TBS/CDC -2 (5415) P3  
© TBS 2018 — All rights reserved                                                                             First edition 2018