How to use a light meter to detect the total acid content of acetate

The acid in fruit wine is brought by raw materials, such as tartaric acid in grapes, malic acid in apples, citric acid in bayberry, etc.; There are also fermentation processes produced such as acetic acid, butyric acid, lactic acid, succinic acid, etc. If the acid content in apple cider vinegar is appropriate, the taste will be mellow, harmonious, and palatable. The opposite is bad.

At the same time, acid also has a certain effect on preventing the reproduction of miscellaneous bacteria. The indicators used in production to express the amount of fruit acids are total acids and volatile acids. The total acid, that is, the total content of substances that form an acidic reaction, has a lot to do with the flavor of apple cider vinegar (the general total acid content of apple cider vinegar is g - 8 g 100 ml).

Volatile acids refer to some acids that evaporate with water vapor, and are calculated as acetic acid in practice (volatile acids in apple cider vinegar should not be higher than 100 ml). It should be said that in the above range, the higher the total acid index of apple cider vinegar, the better!

Draw 5ml of sample, add 20ml of distilled water, drop into 2 drops of phenolphthalein to start titration of the number of sodium hydroxide consumed by the formula: x% (HAC) = C (Naoh) V (NaOH) M (HAC) 100 (1000 V d) where x% represents the percentage concentration of total acid in vinegar; C(NaOH) indicates the concentration of sodium hydroxide used for titration, mol l; V(NaOH) indicates the volume of sodium hydroxide solution consumed by titration.

ml；m(hac) denotes the molar mass of acetic acid, g mol; v indicates the volume of vinegar absorbed for titration, and indicates the density of vinegar, g ml

1. Draw the vinegar sample with a pipette, put it into a 250ml volumetric flask, and then dilute it to the scale with distilled water without CO2, shake it well for later use.

2. Use a pipette to draw the diluted vinegar sample into a 250ml Erlenmeyer flask, and add 2 3 drops of phenolphthalein indicator.

3. Titrate with NaOH standard solution until the solution is reddish and does not fade within 30s as the end point, and record the volume of NaOH standard solution consumed. Measure 3 times in parallel, and the relative average deviation of the results of each measurement is required to be no greater than , and the total acid amount of vinegar is calculated.

Formula: x%(HAC) = C(NaOH) V(NaOH) M(HAC) 100 (1000 V D).

x % indicates the percentage concentration of total acid in vinegar;

C(NaOH) indicates the concentration of sodium hydroxide used for titration in mol l;

V(NaOH) indicates the volume of sodium hydroxide solution consumed by titration. Unit: ml;

m(hac) represents the molar mass of acetic acid in g mol;

v represents the volume of vinegar absorbed for titration, unit: ml;

d indicates the density of vinegar in g ml.

The purpose of the determination of total acid in vinegar is to understand the general preparation and calibration method of alkali standard solution, to master the method of calibrating sodium hydroxide solution with potassium hydrogen phthalate, to learn the determination method of total acid in vinegar, and to learn the basic principle of strong alkali titration of weak acid.

The process is more complicated, and there is readily available information on the Internet for reference.

Aspirate 5 ml of sample

Add 20 ml of distilled water.

Begin titration with 2 drops of phenolphthalein.

The number of sodium hydroxide consumed formula: