How are chloride ions and potassium oxide in potassium chloride reagent? A practical manual with examples

Have you ever encountered this situation: get a bottle?Potassium chloride chemical reagent, the label says "content ≥ 99.5%", and the teacher asks you to report it.What exactly is the chloride ion?The customer asks youIs there 60 points for potassium oxide?? You toss and turn about the molecular weight, but you don't dare to write. Don't panic, we'll figure this out today - by the wayThe steps and methods of using potassium chloride reagent based on potassium oxideIt is also clear that no one will be afraid to ask in the future.

The first level: chloride ion content is actually a proportional problem

There is only one core formula:
Mass fraction of chloride ions = (35.45/74.55) × purity of potassium chloride

Example 1: You have a bottle of analytically pure chemistry with 99.5% KCl in your hand. Please calculate the theoretical percentage of chloride ions in it.

Solution:
35.45 ÷ 74.55 Technologies 0.4755 (this is the mass ratio of Clin pure KCl)
0.4755 × 99.5% ≈ 0.4731 → 47.31%

That is to say, if you weigh 1.0000g of this chemical reagent, there is about 0.4731g of chloride ions in it. If you want to make a chloride ion standard solution, such as a 1000mg/L Clsolution, how much KCl do you need to weigh?
Sample weight = (target concentration × volume × 74.55)/(35.45 × purity) = (1 × 1 × 74.55)/(35.45 × 0.995) Technologies 2.11g - Call this number bandwidth evaluation to 1L.

How to verify the actual measurement? Using the silver nitrate titration method (Mohr method), using potassium chromate as an indicator, the end point changes from yellow to brick red. The dripping volume directly applies the formula above to invert the purity, and the measured chloride ion can be calculated.

Level 2: Convert potassium oxide, remember the magic number "times 1.2"

Fertilizers and industry standards do not directly write "potassium", they must be converted intoPotassium oxide (K2O)This is because it is an internationally accepted expression of active ingredients.

The conversion logic has only two steps:

• The proportion of potassium in pure KCl = 39.10/74.55 Technologies 52.45%
• The coefficient of conversion of potassium to potassium oxide = (K 2O O molecular weight 94.20)/(2 K atomic weight 78.20) = 1.2046 Technologies 1.2

Therefore, a universal formula was born:
Potassium oxide (K 2O O) content = potassium chloride purity × 52.45% × 1.2 = potassium chloride purity × 62.94%

Example 2: An agricultural grade potassium chloride label is marked with KCl ≥ 95%, asking how much potassium oxide is at least?

Solution:
62.94% × 95% = 59.79% - That is the origin of the "60 potassium" often said.

Do the reverse. If the customer requires potassium oxide ≥ 60%, the purity of potassium chloride needs to be at least 60% ÷ 62.94% Technologies 95.3% When purchasing, take this number to the card supplier, no one will try to fool you

Practical exercise: from sample to report, a set of processes goes down

Suppose you want to measure the true potassium oxide content of a batch of potassium chloride samples (The steps and methods of using potassium chloride reagent based on potassium oxideUsually operated according to standard T/QAS 018-2020), the steps are as follows:

1. Accurate weighing: Weigh about 0.15g of sample (accurate to 0.0001g) and dissolve in 50mL of water.
2. Precipitation reaction: Add sodium tetraphenylborate solution to form a white precipitate of potassium tetraphenylborate.
3. Filter and wash: Filter with a constant weight glass sand core crucible until no chloride ions (checked with silver nitrate).
4. Drying and weighing: bake at 105 ° C to constant weight, and weigh the precipitation quality.
5. Calculate the potassium content: potassium mass = precipitation mass × (atomic weight of K/molecular weight of potassium tetraphenylborate), the molecular weight of potassium tetraphenylborate (KB (C H)) is 358.33, and the coefficient = 39.10/358. 33 Technologies 0.1091.
6. Convert potassium oxide: Multiply the mass of potassium by 1.2046 and divide by the mass of the sample to obtain the percentage of potassium oxide.

Example 3: Weigh the sample 0.1523g, get the precipitation quality 0.0865g, find the potassium oxide content.

Solution:
Potassium mass = 0.0865 × 0.1091 = 0.00944g
Mass of potassium oxide = 0.00944 × 1.2046 = 0.01137g
Potassium oxide content = 0.01137/0.1523 × 100% = 7.47% Wait, this number is obviously wrong, because the normal potassium chloride and potassium oxide should be around 60%. It means that the precipitation is not complete or the washing is lost - I encountered abnormal data in actual combatMust be retestedAnd check whether the pH is controlled at a weakly alkaline level (pH 8 to 9), which is the easiest point for the method to overturn.

The scientific grain officer said: If you can calculate it clearly, you must be worthy of it.

No matter how familiar the formula is, if the purity of sodium tetraphenylborate used is not enough and the pore size of the glass sand core crucible is not suitable, you will still get strange data. At this time, a reliable reagent platform is your "logistics confidence".Scientific Grain Officer- Scientific materials intelligence one-stop shopping platform, over 1 million kinds of fine chemicals, from benchmark potassium chloride to sodium tetraphenylborate, silver nitrate, potassium chromate indicator, one-stop supply. "Intelligent manufacturing is only standard, experiment is not too embarrassing", let you spend your energy on calculation and thinking, instead of headaches due to lack of reagents and poor purity.

Remember these two, go around the lab and not be afraid

• Chloride: direct set of 35.45/74 x purity, titration verification.
• Potassium oxide: purity × 62.94%, or the measured potassium is converted by multiplying 1.2.

Next time someone asks you how to calculate chloride ions and potassium oxide in potassium chlorideScientific Grain OfficerThrow him this manual - all the steps, formulas, example problems, no need to flip through the phone. After all, experiments can be rigorous, but the methods must be simple.