IS: 3078 (Part 4) – 1985
DETERMINATION OF TOTAL ALKALINITY
1. SCOPE
1.1 This standard prescribes a method for the determination of total alkalinity of natural rubber
latex of Hevea brasiliensis, uncompounded and unvulcanized and subjected to some type of
concentration process other than heat concentration and which may contain preservatives.
latex of Hevea brasiliensis, uncompounded and unvulcanized and subjected to some type of
concentration process other than heat concentration and which may contain preservatives.
2. OUTLINE OF THE METHOD
2.1 Latex is titrated to pH 6.0 in the presence of a stabilizer, either electrometrically, or
alternatively with methyl red as visual indicator and its alkalinity calculated from the quantity of
acid which is required
alternatively with methyl red as visual indicator and its alkalinity calculated from the quantity of
acid which is required
3. APPARATUS
3.1 PH Meter-equipped with glass electrode and saturated calomel cell and capable of being
read to .02unit.
3.2 Chemical balance
3.3 Weighing bottle
3.4 Burette
read to .02unit.
3.2 Chemical balance
3.3 Weighing bottle
3.4 Burette
4. REAGENTS
4.1Emulsion stabilizer- 5 percent solution of a non-ionic stabilizer of the ethylene oxide
condensate type .Before use, the PH of the solution shall be adjusted to a value of 6.0±0.1.
4.2 Sulphuric acid or Hydrochloric acid- 0.1N
condensate type .Before use, the PH of the solution shall be adjusted to a value of 6.0±0.1.
4.2 Sulphuric acid or Hydrochloric acid- 0.1N
5. PROCEDURE
5.1 Take between 5gm and 10 gm of well mixed sample in a weighing bottle fitted with a
stopper. Weigh to the nearest .01g. To a 500ml squat beaker add 200 ml of water. Mix with
water 10 ml of stabilizer solution. Stir the water with a glass road to distribute the stabilizer.
Pour the latex in to the beaker from the weighing bottle, restopper the bottle and re weigh to
obtain the mass of latex added by difference. Stir to distribute the latex in the stabilizer
solution. Insert the electrodes of the standardized PH meter and, with continual stirring, add
from a burette the sulphuric acid or hydrochloric acid solution until the PH is reduced to a value
of 6.0±.05.Add the acid drop by drop on approaching the end point.
5.2 As an alternative to electrometric titration, use methyl red as visual indicator, taking the
end point as the colour change to pink.
stopper. Weigh to the nearest .01g. To a 500ml squat beaker add 200 ml of water. Mix with
water 10 ml of stabilizer solution. Stir the water with a glass road to distribute the stabilizer.
Pour the latex in to the beaker from the weighing bottle, restopper the bottle and re weigh to
obtain the mass of latex added by difference. Stir to distribute the latex in the stabilizer
solution. Insert the electrodes of the standardized PH meter and, with continual stirring, add
from a burette the sulphuric acid or hydrochloric acid solution until the PH is reduced to a value
of 6.0±.05.Add the acid drop by drop on approaching the end point.
5.2 As an alternative to electrometric titration, use methyl red as visual indicator, taking the
end point as the colour change to pink.
6. CALCULATION
6.0 Calculate the alkalinity of the latex as specified in 6.1 or 6.2 whichever is appropriate.
6.1 If the latex is preserved with ammonia, calculate its alkalinity as grams of ammonia per
100Kg of latex, as follows.
Alkalinity (as NH3) = 1.7×N×V
M
Where
N= normality of the acid used
V= volume in ml of acid used
m= mass in gm of the test portion
The result of the duplicate determinations shall not differ by more than .02 unit where the
actual alkalinity is above 0.5 unit, or shall not differ by more than .01 unit where the actual
alkalinity is 0.5 unit or less.
6.1 If the latex is preserved with ammonia, calculate its alkalinity as grams of ammonia per
100Kg of latex, as follows.
Alkalinity (as NH3) = 1.7×N×V
M
Where
N= normality of the acid used
V= volume in ml of acid used
m= mass in gm of the test portion
The result of the duplicate determinations shall not differ by more than .02 unit where the
actual alkalinity is above 0.5 unit, or shall not differ by more than .01 unit where the actual
alkalinity is 0.5 unit or less.
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