This standard specifies the test method of total acid in liquor.
This standard is applicable to the determination of total acids in various aromatic liquors.
Principle 2
With phenolphthalein as indicator, the organic acid in the titration solution is neutralized with sodium hydroxide, and the reaction formula is as follows:
RCOOH + NaOH ── RCOONa + H2O
Three testing methods
3. 1 reagent
3. 1. 1. 1% phenolphthalein indicator: weigh phenolphthalein 1.0g, dissolve it in 60mL ethanol and dilute it to 100mL with water.
3. 1.2 0. 1mol/L sodium hydroxide standard solution.
A. Preparation
Mix sodium hydroxide into a saturated solution, pour it into a plastic bottle (or barrel), put it in a closed place until the solution is clear, and siphon it before use.
supernatant
Measure 5mL of saturated sodium hydroxide solution, inject it into 1 000mL of water without carbon dioxide, and shake well.
B. Calibration
Weigh 0.6g (calibrated to 0.0002g) of benchmark potassium hydrogen phthalate baked at 105 ~ 1 10℃ and dissolve it in 50mL.
Add 2 drops of phenolphthalein indicator solution to water without carbon dioxide, and titrate with newly prepared sodium hydroxide solution until the solution becomes weak.
Red is its destination. At the same time, do blank test.
C. calculation
The molar concentration (c) of sodium hydroxide standard solution is calculated according to the formula (1):
m
c =━━━━━━━━ 1
(V - V 1)× 0.204 2
Where: c-concentration of sodium hydroxide standard solution, mol/l;
M—— the quality of reference substance potassium hydrogen phthalate;
V—— the volume of sodium hydroxide solution consumed during titration, ml;
V 1—— the volume of sodium hydroxide solution consumed in blank test, ml;
0.2042-equivalent to 1.00mL sodium hydroxide standard solution [C (NaOH) = 1.000 mol/L].
Quality of potassium hydrogen phthalate.
3.2 test procedures
Suck 50.0 ml of wine sample into a 250 ml conical flask and add 2 drops of phenolphthalein indicator; With 0. 1 mol/L sodium hydroxide as the standard.
The end point of quasi-solution titration is reddish.
4 calculation
c×V×0.060 1
x =━━━━━━× 1 000 …………………( 2)
50.0
Where: X refers to the total acid content in the wine sample (calculated by acetic acid), g/L;
C—— concentration of sodium hydroxide standard solution, mol/l;
V—— the volume of sodium hydroxide standard solution consumed during determination, ml;
0.060 1—— equivalent to 1.00mL sodium hydroxide standard solution [C (NaOH) = 1.000 mol/L], expressed in grams.
Quality of acid;
50.0—— Sampling volume, milliliter (mL).
5 Allowable result difference
The difference between the two measured values of the same sample shall not exceed 0.006g/L, and two decimal places shall be reserved, and the results shall be reported.