ISO 685-2020 pdf free.Analysis of soaps — Determination of totalalkali content and total fatty matter content.
total alkali:sum of the alkali bases combined as soap with fatty and rosin acids, as well as those corresponding tofree alkali metal hydroxides or carbonates and to any silicates present which will be titrated under thetest conditions
Note 1 to entry:The results are expressed as a percentage mass fraction of either sodium hydroxide(NaOH)or ofpotassium hydroxide (KOH), according to whether sodium or potassium soaps are concerned.
total fatty matter:water-insoluble fatty material obtained by decomposing the soap with a mineral acid under theconditions specified
Note 1 to entry:This term includes unsaponifiable matter, glycerides and any rosin acids contained in the soap,in addition to the fatty acids.
Decomposition of the soap by a known volume of standard volumetric mineral acid solution, extractionand separation of the liberated fatty matter with light petroleum and determination of the total alkalicontent by titration of the excess of acid contained in the aqueous phase with a standard volumetricsodium hydroxide solution.After evaporation of the light petroleum from the extract, dissolution ofthe residue in ethanol and neutralization of the fatty acids with a standard volumetric potassiumhydroxide solution.Evaporation of the ethanol and weighing of the soap formed to determine the totalfatty matter content.
Dissolve the test portion (8.2) in about 100 ml of hot water.
Pour the solution into one of the separating funnels (6.2) or into the extraction cylinder (6.3) andwash the beaker with small quantities of water, adding the washings to the separating funnel or to theextraction cylinder.
Add a few drops of the methyl orange solution (5.7) and then, from a burette, add, while vigorouslyshaking the separating funnel or the extraction cylinder, an accurately measured known volume of thesulphuric acid solution (5.4)until there is an excess of about 10 ml.Cool the contents of the separatingfunnel or of the extraction cylinder to about 25 C and add 100 ml of the light petroleum(5.2). Insertthe stopper and gently invert the separating funnel or the extraction cylinder, while maintaining a holdon the stopper: Open the stopcock of the separating funnel or the stopper of the extraction cylindergradually to release any pressure, then close, gently shake and again release the pressure.Repeat theshaking until the water phase is clearly separated from the organic phase (if the two-phase layer is notobvious, the emulsification can be broken by adding ethanol that does not exceed the volume of thewater phase), and then allow to stand.ISO 685 pdf download.