Compound fertilizer potassium chloride composition analysis.

Preparation of fully water soluble fertilizer potassium chloride sample solution

Weigh about 3g of the sample (containing about 400mg of potassium oxide), accurate to 0.0001g, place it in a 250ml Erlenmeyer flask, add about 150ml of water, heat and boil for 30 minutes, cool, quantitatively transfer to a 250ml measuring flask, and dilute to the mark with water , mix well, dry filter, discard the first 50ml filtrate.

Water soluble fertilizer potassium chloride test solution pretreatment

Take 25.0ml of the above filtrate, place it in a 200ml beaker, add 20ml of EDTA solution, add 2 to 3 drops of phenolphthalein solution, add sodium hydroxide solution dropwise until red appears, add 1ml to the excess, slowly heat and boil in a good fume hood 15 minutes, then let it cool to room temperature. If the red color disappears, use sodium hydroxide to adjust it to red color.

Precipitation and filtration of fully water soluble potassium chloride fertilizer solution

Under constant stirring, add sodium tetraphenylborate solution dropwise to the sample solution. The amount added is 1 mg of potassium oxide plus 0.5 ml of sodium tetraphenylborate solution, with an excess of about 7 ml. Continue stirring for 1 minute and let it stand for more than 15 minutes. Use the pouring filtration method to filter the precipitate and dry it at 120°C to a No. 4 glass crucible filter with constant weight. Wash the precipitate 5 to 7 times with sodium tetraphenylborate washing solution, using about 5 ml each time, and then wash it 2 times with water. Each dosage is 5ml.

Potassium chloride solution drying

Place the crucible containing the precipitate in a drying oven at 120±5°C, dry for 1.5 hours, then place it in a desiccator to cool and weigh.

How to calculate potassium chloride composition of water soluble npk fertilizer- step by step guide

The first step of calculating the KCL composition of fully water soluble compound fertilizer is using this equation: The potassium content is expressed as the mass fraction of potassium oxide X4 (K2O)%, calculated according to formula:

• X4=(m2-m1)*131.4/M0

In the formula:

1. m2——The mass of the precipitate obtained from the test solution, unit (g)
2. m1——The mass of the precipitate obtained during the blank test, unit is (g)
3. 0.1314——Coefficient for converting the mass of potassium tetraphenylborate into the mass of potassium oxide
4. m0——The mass of the sample, unit is (g)

Take the arithmetic mean of the parallel measurement results as the measurement result. 

Standard deviation: The absolute difference between parallel measurement results shall not be greater than 0.30%.

5 Precautions during the determination of KCL content in water-soluble fertilizers

1. The amount of sodium hydroxide solution added when processing the test solution should be strictly controlled. The main way to remove the interference of ammonium is to add excess sodium hydroxide solution to generate ammonium hydroxide and then heat it to drive out ammonium. If the amount of sodium hydroxide solution added is not enough, the interference in the test solution will be eliminated. If the ammonium ions are not completely removed, a positive deviation will occur.
2. During the treatment of the test solution, the heating temperature should not be too high, and the boiling time should be controlled at 15 minutes as specified. Otherwise, the test solution will be concentrated, the sodium ion concentration will increase, and a positive deviation will occur.
3. The number and dosage of sedimentation washes must be strictly followed, otherwise the results will be low.
4. Precipitation drying temperature. The drying temperature of potassium tetraphenylborate precipitate should not exceed 130℃, and the precipitate will gradually decompose if it is higher than 130℃. Also pay attention to the accuracy of the drying oven temperature.
5. Disposal of used crucibles. The crucible containing potassium tetraphenylborate precipitate should first be soaked in dilute hydrochloric acid, then rinsed and filtered with water. The precipitate may still remain, and a small amount of acetone should be used for further flushing.

Compound fertilizer free water measurement experiment

In a pre-dried and constant-weight weighing bottle, weigh 2g of the sample, weigh accurately to 0.0001g, place it at 50°C ± 2°C, and use a dryer to adjust the vacuum degree to 6.4×104Pa ~ 7.1×104Pa in an electric constant-temperature vacuum. Dry in the drying box for 2h±10min, take it out, cool to room temperature in the desiccator, and weigh.

Compound fertilizer free water measurement calculation formula

The content of free water is calculated as mass fraction X5 (free water) (%), calculated according to formula:

• X5=(m-m1)/m*100

In the formula:

1. m——Mass of sample before drying, unit is grams, (g)
2. m1——Mass of sample after drying, unit is grams, (g)

Take the arithmetic mean of the parallel measurement results as the measurement result.
Standard deviation: The absolute difference of parallel measurement results should be ≤0.20%.

What are the precautions during the process?

1. The samples weighed into the weighing bottle should be evenly covered.
2. Temperature and vacuum should be strictly controlled.

Conclusion: composition analysis of fully water-soluble potassium compound fertilizer

Potassium is an element that is very important to plants and can help plant leaves grow fuller. In this article, we introduce how to turn granular compound fertilizer into a solution, and then use the solution to test whether the ingredients of the compound fertilizer meet the standards. At the same time, we also introduced how to test how much free water is contained in compound fertilizers. In our next article, we will introduce more knowledge about compound fertilizers.