Food grade calcium phosphate is an important fine phosphate products, can be widely used in food, biological composite materials, antibacterial materials, high-grade handicrafts, synthetic plastic, toothpaste, pharmaceuticals, and other fields. Global food grade calcium phosphate in the annual consumption of more than 650 thousand tons, and annual growth rate of 5% to 3%, while the quality of calcium phosphate requirements are also getting higher and higher.

Lianyungang Shuren Kechuang Food Additive Co., Ltd. in 1998 to enter the food additives industry, more than 20 years of industry experience, in support of the provincial science and Technology Department, Lianyungang Shuren Kechuang Food Additive Co., Ltd. in 1998 started food grade calcium phosphate production technology research and development. Development of food grade calcium phosphate products, sold worldwide.

Experimental principle

Phosphoric acid, calcium phosphate, chemical formula Ca3 (PO4) 2. White crystal or amorphous powder, soluble in acid, insoluble in water and alcohol. Hydrochloric acid can be dissolved phosphate calcium phosphate, added to the quantitative Bi3+ salt, Bi3+ and PO43- to generate BiPO4 precipitation, filtration removal. The PK stability (BiEDTA =27.94, alpha H (y) |PH=1.0=18.01, and PK stability (CaEDTA) =10.69, so at pH = 1, can be individually titrated Bi3 +, calculated PO43 -. In addition Ksp (Bi (OH) 3) =4.0 * 10-31, so it can be in the PH = 12 case of single Ca2+ titration.

Some calculation

1 Bi3+ titration of PH:

The highest acidity: lgaY (H) =lgKBiY--8=27.94-8=19.94 that is pH low =0.7

Minimum acidity: 10-10 * [OH-]=

PH high =14-pOH=14-9.56=4.4

Hence Bi3+ is accurate titration pH range: 0.7 ~ 4.4

Optimal conditional access

2 Ca2+ titration of PH:

The highest acidity: lgaY (H) =lgKCaY2 - -8=10.69-8=2.69, that is, pH high =7.6

Minimum acidity: [OH-]= 0.016

PH low =14-pOH=14-1.80=12.2

Hence Ca2+ is accurate titration pH range: 7.6 ~ 12.2

But the Ca2+ in the PH = 12 by titration

3 bismuth phosphate precipitation conditions

4 reagent dosage

Experimental procedure

1 EDTA calibration

Accurately known as the benchmark CaCO3 0.5g, hydrochloric acid dissolved in the 250mL capacity of the bottle. 3.7g is about EDTA-2Na, 500mL water solution. Take 25.00mL calcium standard solution, adding proper amount of malachite green, with 20% NaOH adjusted to colorless, excessive a few drops, a small amount of precipitate, adding a small amount of calcium indicator, titrated with EDTA solution to the red change to blue as an end.

2 Bi3+ standard solution

Weighing about 4.8g Bi (NO3) 3 - 5H2O, with a small amount of nitric acid, regulating PH = 1-2 diluted with water.

3 sample treatment

Accurately take 1.77gCa (NO3) 2 - 4H2O dissolved in water, 1.90gNa3PO4 - 12H2O. With a small amount of 1:1 nitric acid to dissolve after dilution, mixing, regulating pH = 1-2, adding 2 standard Bi (NO3) 3 (including the amount of washing part), precipitate, standing, filtering, washing, filtrate transferred into 250 ml volumetric flask, constant volume.

3 Determination of PO43- content

Remove the test 25.00mL in a conical flask, add a small amount of xylenol orange, with EDTA standard solution for titration till the solution from purple to red variable light yellow is for determination of Bi3 + end can be calculated PO43 - content.

4 Determination of Ca2+ content

Remove the test 25.00mL in a conical flask, adding proper amount of malachite green, with 20% NaOH adjusted to colorless, when there is a lot of precipitation was generated, remove the filter filtrate join a small amount of calcium indicator, titrated with EDTA to the solution from red to become blue is the end point can be calculated Ca content.