ISO 685-1975 pdf free.Analysis of soaps — Determination of total alkali contentand total fatty matter content.
This lInternational Standardspecifies a methodforthe simultaneous determination of the total alkali1)contentand the total fatty matter content of soaps,excluding compounded products.
This method for the determination of tolal alkali is notapplicabie to coloured soaps if the colour interferes withthe methyl orange end-point.
For the purposesofthis International Standard, thefollowing definitions apply :
total alkali : The sum of the alkali bases combined as soapwith fatty and rosin acids, as welt as those corresponding tofree alkali metal hydroxides or carbonates and to anysilicates present which will be titrated under the testconditions.
The results are expressed as a percentage by mass of eithersodium hydroxide (NaOH)or of potassium hydroxide( KOH)，according to whether sodium or potassium soapsare concerned.
total fatty matter : The water-insoluble fatty materialobtained by decomposing the soap with a mineral acidunder the conditions specified. Thisterm includesunsaponifiable matter,glycerides and any rosin acidscontained in the soap,in addition to the fatty acids.
4PRINCIPLE
Decomposition of the soap by a known volume of standardvolumetric mineral acid solution，extraction and separationof the liberated fatty matter with light petroleum and determination of the total alkali content by titration of theexcess of acid contained in the aqueous phase with astandard volumetric sodium hydroxide solution. Afterevaporation of the light petroleum from the extract,dissolution of the residue in ethanol and neutralization ofthe fattyacids with a standard volumetric potassiumhydroxide solution. Evaporation of the ethanol andweighing of the soap formed to determine the total fattymatter content.During the analysis，use onlyreagents of recognizedanalytical reagent grade and only distilled water or water ofequivalent purity.
Dissolve the test portion (8.1) in about 100 ml of hotwater.
Pour the solution into one of the separating funnels (6.2)orinto the extraction cylinder (6.3) and wash the beaker withsmall quantities of water,adding the washings to theseparating funnel or to the extraction cylinder.
Add a few drops of the methyl orange solution (5.7) andthen. from a burette，add，while vigorously shaking theseparating funnel or the extraction cylinder, an accuratelymeasured known volume ofthe sulphuricacid orhydrochloric acid solution (5.4) until there is an excess ofabout 5 ml.Cool the contents of the separating funnel or ofthe extraction cylinder to about 25°c and add 100 ml ofthe light petroleum (5.2). Insert the stopper and gentlyinvert the separating funnel or the extraction cylinder,whilst maintaining a hold on the stopper. Open the stop-cock of the separating funnel or the stopper of theextraction cylinder gradually to release any pressure，thenclose，gently shake and again release the pressure.Repeatthe shaking until the aqueous layer has become clear,andthen allow to stand.
a) ln the case of use of separating funnels Run off the aqueous layer into a second separatingfunnel (6.2)and extract with 50 ml of the . lightpetroleum (5.2). Repeat the process, collect the aqueouslayer in a conical flask and combine the three lightpetroleum extracts in the first separating funnel.
b) ln the case of use of an extraction cylinder Using a siphon，draw off the light petroleum layer ascompletely as possible into a separating funnel (6.2).ISO 685 pdf download.