**ppm: Parts per Million**

**Introduction:**
Parts per million (ppm) is a unit used to express the concentration of a substance in a solution or mixture. It is commonly used in various fields such as chemistry, environmental science, and engineering. The ppm value represents the number of parts of a particular component per one million parts of the whole mixture.

**Formula:**
The formula to calculate ppm is:

ppm = (mass of solute / mass of solution) x 10^6

Where:
- ppm is the concentration in parts per million.
- Mass of solute is the mass of the component being measured.
- Mass of solution is the total mass of the solution or mixture.

**Explanation:**
To understand the formula in detail, let's break it down into its components and explain each part.

1. **Mass of Solute:**
The mass of solute refers to the mass of the component that you want to measure the concentration of. For example, if you want to determine the concentration of a specific chemical in a solution, the mass of that chemical would be the mass of solute.

2. **Mass of Solution:**
The mass of solution is the total mass of the entire solution or mixture. It includes the mass of both the solute and the solvent. The solvent is the substance in which the solute is dissolved. In most cases, the solvent is present in a larger quantity compared to the solute.

3. **Multiplication by 10^6:**
The multiplication by 10^6 is necessary to convert the concentration into parts per million. One million is equivalent to 10^6. This step ensures that the concentration is expressed as a ratio of parts to a million parts.

4. **Final Calculation:**
By dividing the mass of solute by the mass of solution and multiplying it by 10^6, we obtain the concentration of the solute in parts per million. This value represents the number of parts of the solute present in one million parts of the solution or mixture.

**Example:**
Let's illustrate the formula with an example. Suppose we have a solution with a mass of 500 grams and it contains 2 grams of a specific substance. To find the concentration of this substance in ppm, we can use the formula:

ppm = (2 g / 500 g) x 10^6

ppm = 4,000 ppm

Therefore, the concentration of the substance in the solution is 4,000 parts per million.

The basic formula is weight (or number of defects) divided by volume multiplied by 1,000,000 – or w/v x 1,000,000. For example, if you have 100 defective products in 10,000 manufactured pieces, divide 100 by 10,000 to arrive at the result of 0.01 or 1 percent of the total. Then, multiply 0.01 by 1,000,000 to achieve the answer of 10,000defective parts per million parts produced.