Stock solutions
By the end of this lesson
- Identify a stock solution completely
- Keep each chemical concentration separate
- Use source guidance for stability and storage
Examples use a decimal point; a comma groups thousands.
See it
A stock solution contains a known concentration of a substance so that a smaller measured volume can be added to the final preparation. Stocks improve repeatability only when identity, concentration, solvent/diluent, storage, and version are clearly recorded.
Understand it
Identify a stock solution completely
Label stock identity and concentration unambiguously.
A stock is useful for repeatable dosing when its chemical identity and concentration are known.
Keep each chemical concentration separate
Keep stock concentration separate for each chemical.
Preparation medium and storage/stability context help determine whether a labeled stock is appropriate to use.
Use source guidance for stability and storage
Expiration or stability information should come from appropriate source/product guidance.
Amount added depends on concentration as well as volume; 1 mg/mL and 0.1 mg/mL are not equivalent stocks.
Worked example
Two bottles carry the same chemical name but one is labeled 1 mg/mL and the other 0.1 mg/mL. Equal draws would add different amounts. Check the actual stock label and its preparation record before calculating a draw.
Explain your decision before opening the worked reasoning below.
Show the worked reasoning
Stability and storage are chemical/product-specific; they should not be invented from a generic stock example.
A chemical name alone cannot support a stock-volume calculation; resolve the missing concentration first.
Never assume two stocks with similar labels have the same concentration.
Try it
Do equal draws from the example's two stocks add equal amounts?
Use the worked example above to explain your answer in your own words before taking the quiz.
Lesson quiz
Assessment version: 2026-10-15-v2. Previous reading-completion markers are retained. This revised quiz has its own result.
Apply it
Use the worked example to write a short decision record: what did you observe, which rule did you apply, and what would you check before acting?
Completion marks reading progress, not a quiz pass or professional certification.