Dangerous Chemical Spill at Lucas Heights

This is a headline from the Sydney Morning Herald, Friday 1^st March 2019, "Three hospitalised after chemical spill at Lucas Heights nuclear facility" and an excerpt from the newspaper story is below:

"Two men in their 30s, and a woman, 26, were injured when a cap came off a pipe at the Australian Nuclear Science and Technology Organisation facility at Lucas Heights, spilling about 250 millilitres of sodium hydroxide, also known as caustic soda, onto their arms and faces.

 Sodium hydroxide, also known as caustic soda, is corrosive to the skin and eyes and can cause severe burns."

This "sodium hydroxide" or "caustic soda" sounds like really dangerous stuff doesn't it?  I mean to say, it must be if just 250 mL (a quarter of a litre, a bit less than half a pint)  causes 3 people in an up-to-date, modern, nuclear-medicine manufacturing building, to be hospitalized!

 Well, sodium hydroxide is a caustic substance, that is, corrosive to skin, and it is dangerous if handled incorrectly, however, it is also readily available to non-scientists! You will probably find sodium hydroxide in your own home.

Sodium hydroxide is commonly found in household cleaning products that are used to unblock drains. One such product is Mr Muscle Drano  The directions for use including the following:

WEAR EYE PROTECTION AND PROTECTIVE GLOVES WHEN MIXING OR USING. AVOID CONTACT WITH EYES AND SKIN. DO NOT MIX WITH HOT WATER. 

Keep hands and face away from drains and wash hands after use. Ensure adequate ventilation.
• Do NOT mix with other cleaning products or acids as it may give off a dangerous gas
• Open carefully, do not squeeze the bottle, avoid splashing and clean up spills at once.
• Never use a plunger during or after use, as there may be some Mr Muscle® Drano® in the pipe if the blockage did not completely clear.
• Do NOT use in spas, dishwashers, washing machines, rubbish disposals, toilets or any pipes leading to these outlets. Will not remove roots, leaves or non-organic matter. Always refer to product label for full directions.

You will find sodium hydroxide pellets ("crystals") are also readily available, the website of one such product even suggests you use it to make your own soap ...

METHOD 

1. READ THE DANGEROUS GOODS INFORMATION BELOW BEFORE BEGINNING THIS RECIPE. 

2. Pour cold water into the plastic jar. 

3. Measure Glitz Caustic Soda (into a dry plastic cup).

 4. Slowly and carefully add the Glitz Caustic Soda to the cold water, stirring continuously with a plastic rod. (Wear plastic gloves and goggles; test gloves for holes first.) Do not breath the vapor or lean over the container or have children nearby. The mixture will get very hot.  

5. Allow the solution to cool down to a warm temperature (approx 40oC) in a safe place. 

 6. Melt the Coconut Oil (Copha) at a low heat in a stainless steel saucepan. Add the Canola Oil and Olive Oil to the melted Coconut Oil. Mix well 

7. Allow the oil mixture to cool down to a warm temperature (approx 40oC)

 8. Slowly and carefully, pour the Caustic Soda solution into the stainless steel saucepan containing the oil mixture. Mix thoroughly for at least 30 minutes or until it looks like thick pudding. 

9. If desired, select one fragrance from the optional fragrances. Add the fragrance to the soap mixture and mix for a further 30 minutes.  

10. Pour the finished soap into the tupperware container and allow 24hrs of setting. 

11. Cut the set soap into bars and leave it to cure for at least 6 weeks before use

But honestly, making your own soap at home might sound like fun, but unless you fully understand what you are doing then you should NOT use your soap to wash yourself or you might be the one that is rushed to hospital!

Suggested further reading:
Properties of Acids and Bases 
Definitions of Acids and Bases 
Strength of Bases
Heat of Solution
Neutralisation Reactions 
Heat of Neutralisation
Safety in the Lab 
Soaps and Saponification

Suggested Study Questions:

1. Sodium hydroxide is a caustic substance. What GHS (Globally Harmonised System) pictogram would you find on a container of sodium hydroxide.
2. Sodium hydroxide is a caustic substance. What personal protective equipment (PPE) should you use when handling sodium hydroxide?
3. Write a set of instructions, including all required safety precautions, for dissolving 1 g of sodium hydroxide in 1 L of water.
4. Consider the instructions for using Mr Muscle Drano. Why do you think it advises you to NOT use the product in dishwashers, washing machines and toilets?
5. Consider the instructions for using Mr Muscle Drano. Why do you think it advises you to use ONLY in well ventilated areas?
6. Consider the instructions for making soap. Should you use a plastic drinking cup from the kitchen to measure out the caustic soda? Explain your answer.
7. Why do the soap-making instructions tell you to add the caustic acid to the water AND NOT tell you to add the water to the caustic soda? Do you think it matters which you do this step? Explain your answer.
8. The soap-making instructions tell you to use a stainless steel saucepan. Do you think it would matter if you used an aluminium saucepan or a glass saucepan? Explain your answer.
9. Do you think it is advisable to use a saucepan from the kitchen to make soap? Explain your answer.
10. Imagine you were at the Lucas Heights facility when 3 of your co-workers were injured in this chemical spill. What would you do first to help them?

What is the pH of a Strong Base After You Dilute It?

The problem with strong bases like sodium hydroxide and potassium hydroxide are that they absorb moisture from the air making it difficult to accurately weigh them. So we rely heavily on obtaining an accurately known concentration for an aqueous solution of a strong base (using titration techniques for example) and then diluting this stock solution to produce new, dilute solutions of known concentration and pH.
When you dilute an aqueous solution of a strong base :

• hydroxide ion concentration decreases (towards 10^-7 M)
• pOH increases (towards 7)
• hydrogen ion concentration increases (towards 10^-7 M)
• pH decreases (towards 7)

Visit AUS-e-TUTE's new tutorial to understand why, then log-in to the Members ONLY area to play the game, answer test and exam questions (which give you instant feedback), take the quiz, or, just for teachers, you could make a printable worksheet or quiz.

pH of Weak Acid After Dilution

What happens to the pH of a solution of weak acid, such as acetic acid, if you dilute it by adding water to it?
How much water would you have to add to 100 mL of 0.20 mol L^-1 acetic acid in order to make a solution with a pH of 3.0 ?
What is the pH of 1 × 10^-11 mol L^-1 acetic acid?
AUS-e-TUTE can help you answer these questions with our new resources.
AUS-TUTE Members should log-in to access the new "pH of Weak Acid After Dilution" tutorial, game and test (with worked solutions).
A "free-to-view" tutorial is currently available for non-members at:
https://www.ausetute.com.au/phdilwa.html

Effect of Dilution on pH of Strong Acid Solution

Need to know what the pH of your hydrochloric acid is after you dilute it?
Need to know how much water to add to your hydrochloric acid to make a solution with a particular pH?
AUS-e-TUTE has just added a new tutorial, game, test and exam to help you with this.
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If you're not an AUS-e-TUTE Member, there is a "free-to-view" tutorial currently available at https://www.ausetute.com.au/phdilsa.html

Dilution Factors

I've always thought that an understanding of dilution factors can make a Chemistry student's life a whole lot easier, but at the same time, always avoided teaching it (or indeed making reference to it) because of the muddle students make of it (thinking that every calculation involving a solution can be dealt with using dilution factor "formulae") .... and even worse, biology students always seem to have a desire to just "add volumes" together (even if the volumes are not additive!).

The new dilution factor resources are available to AUS-e-TUTE Members in the Members Only area (and teachers will find a worksheet wizard in the Teachers Area).

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