Acids and Alkalis

Why This Matters

Acids and alkalis are the foundation of all chemistry. Without them, you cannot tan leather, make soap, refine metals, produce fertilizers, clean wounds, or create any of the chemical processes that separate a subsistence camp from an advancing civilization. Understanding how to produce, test, measure, and safely handle these substances unlocks the entire chemical technology tree.

Understanding Acids and Bases

What Are They?

In practical terms:

• Acids taste sour, dissolve metals, and turn plant indicators red. Examples: vinegar, lemon juice, stomach acid.
• Bases (alkalis) taste bitter, feel slippery, and turn plant indicators blue/green. Examples: lye, wood ash water, lime water.
• Neutral substances are neither acid nor base. Pure water is neutral.

When an acid and a base react together, they neutralize each other, producing a salt and water:

acid + base → salt + water
vinegar + baking soda → sodium acetate + water + CO2
hydrochloric acid + lye → common salt + water

This reaction is the single most important concept in chemistry. Every process described below relies on it.

The pH Scale

pH measures how acidic or basic a solution is, on a scale from 0 to 14:

pH	Classification	Examples
0-1	Strong acid	Battery acid, concentrated sulfuric
2-3	Moderate acid	Lemon juice, vinegar, stomach acid
4-5	Weak acid	Tomato juice, beer, acid rain
6	Slightly acidic	Milk, urine
7	Neutral	Pure water
8-9	Slightly basic	Seawater, baking soda solution
10-11	Moderate base	Soap solution, milk of magnite
12-13	Strong base	Lime water, household ammonia
14	Very strong base	Concentrated lye

Concentration vs Strength

A strong acid (like hydrochloric) fully dissociates — even a dilute solution is aggressive. A weak acid (like vinegar) only partially dissociates — even concentrated, it is less dangerous than dilute hydrochloric acid. Never assume safety from the word “dilute.”

Making Plant Indicators

Before you can work with acids and bases, you need a way to test pH. Nature provides excellent indicators.

Red Cabbage Indicator (Best Universal Indicator)

Red cabbage contains anthocyanins that change color across the entire pH range:

1. Chop half a red cabbage finely
2. Boil in just enough water to cover for 15-20 minutes
3. Strain — the deep purple liquid is your indicator
4. Store in a sealed container in a cool place (lasts 1-2 weeks)

Color chart:

Color	pH	Meaning
Red	2	Strong acid
Pink	4	Moderate acid
Purple	6	Weak acid
Violet	7	Neutral
Blue	8	Weak base
Blue-green	10	Moderate base
Green	12	Strong base
Yellow	14	Very strong base

Other Plant Indicators

Plant Material	Acid Color	Neutral	Base Color
Red cabbage	Red/pink	Purple	Green/yellow
Litmus lichen	Red	Purple	Blue
Turmeric	Yellow	Yellow	Red-brown
Red rose petals	Red	Pink	Green
Elderberry juice	Red	Purple	Blue-green
Beetroot juice	Red	Purple	Yellow

Make Test Strips

Soak strips of absorbent cloth or paper in indicator solution and let them dry. You now have portable pH test strips. Dip in your solution and compare the color to your reference chart. Much more convenient than carrying liquid indicator.

Using Litmus

True litmus comes from specific lichens (Roccella, Lecanora species) found on coastal rocks:

1. Collect the lichen and dry it
2. Grind to powder and soak in water with a small amount of ammonia (from urine) for days
3. The resulting solution turns red in acid, blue in base
4. This is the classic litmus test used for centuries

Producing Lye (Alkalis)

Wood Ash Lye (Potassium Carbonate / Potash)

You already know this from Soap Making, but here is the refined process:

1. Burn hardwood (oak, ash, hickory) completely to white/grey ash
2. Build a leaching barrel: a wooden barrel with a drain hole near the bottom, stuffed with straw as a filter
3. Fill with ash and pour water through slowly
4. Collect the brown liquid that drains out — this is lye (potassium carbonate solution)
5. For stronger lye, pour the collected liquid back through fresh ash

Testing lye strength (the egg float test):

1. Place a fresh egg in the lye solution
2. If the egg sinks — too weak, re-leach through more ash
3. If it floats just below the surface with a coin-sized area exposed — correct strength for soap
4. If it floats high — too strong, dilute with water

Hardwood vs Softwood

Hardwood ash (oak, maple, beech) produces potassium-rich lye — better for soap and cleaning. Softwood ash (pine, spruce) produces weaker, more resinous lye. Always prefer hardwood.

Caustic Lye (Sodium Hydroxide / Caustic Soda)

For stronger, more caustic lye (needed for hard soap and some chemical processes):

1. Make lime water: add slaked lime (calcium hydroxide) to water, stir, let settle
2. Make soda ash solution (see below): dissolve soda ash in water
3. Mix the two solutions together
4. A white precipitate of calcium carbonate forms and settles
5. Filter the clear liquid — this is sodium hydroxide (caustic soda) solution

Ca(OH)2 + Na2CO3 → 2 NaOH + CaCO3↓
lime      soda ash    caustic soda   chalk (settles)

Caustic Burns

Sodium hydroxide (caustic soda) will cause severe chemical burns on contact with skin. It dissolves fat and protein — including yours. Always wear eye protection, keep water nearby for flushing, and store in clearly labeled containers away from children and food.

Producing Soda Ash (Sodium Carbonate)

Soda ash is a critical industrial alkali used in glass making, soap production, and water softening.

From Seaweed

1. Collect large quantities of kelp or other seaweed
2. Dry thoroughly in the sun
3. Burn in a pit or trench — the ash should be white-grey
4. Dissolve the ash in water and filter
5. Boil the filtered solution to evaporate water
6. The residue is crude soda ash (mixed with other salts)
7. Re-dissolve and recrystallize to purify

From Mineral Deposits

In arid regions, natron (natural sodium carbonate) forms as a mineral deposit around alkaline lakes. If you find it:

1. Collect the white/grey mineral crust
2. Dissolve in water and filter to remove sand and clay
3. Evaporate to crystallize

From Salt (Leblanc Process — Simplified)

If you have access to common salt, sulfuric acid, limestone, and charcoal:

1. React salt with sulfuric acid to make sodium sulfate (salt cake) and hydrochloric acid gas
2. Mix sodium sulfate with charcoal and limestone
3. Heat strongly in a furnace
4. The product (black ash) contains sodium carbonate
5. Dissolve in water, filter, and evaporate to crystallize

This is an advanced process requiring significant infrastructure, but it was the foundation of the industrial chemical industry.

Vinegar Production (Acetic Acid)

Vinegar is the most accessible acid and has hundreds of uses: preserving food, cleaning, descaling, and as a chemical reagent.

The Two-Stage Process

Vinegar production requires two fermentations:

Stage 1: Make Alcohol Any sugar source works — fruit juice, honey water, grain mash:

1. Crush fruit or dissolve honey/sugar in water (8-15% sugar content)
2. Add yeast (wild yeast on grape skins works, or save commercial yeast)
3. Cover loosely (gas must escape) and ferment in a warm place for 1-2 weeks
4. When bubbling stops, you have wine/mead/beer (5-10% alcohol)

Stage 2: Acetify (Convert Alcohol to Vinegar)

1. Pour the alcohol into a wide, shallow container (maximum surface area for air exposure)
2. Cover with cloth (keeps flies out, lets air in)
3. Add a splash of existing vinegar or “mother of vinegar” if you have it
4. Place in a warm spot (25-30 C is ideal)
5. Wait 2-6 weeks, stirring occasionally
6. A gelatinous film (mother of vinegar) will form on the surface — this is good, it is the Acetobacter culture doing the work
7. Taste periodically — when sour and no longer sweet or alcoholic, it is ready

Save the Mother

The mother of vinegar is a living colony of acetic acid bacteria. Save it and use it to start future batches — it speeds the process dramatically. Store in a jar of vinegar.

Concentrating Vinegar

Standard vinegar is about 4-8% acetic acid. For chemical use, you may need stronger:

• Freezing method: Freeze vinegar partially — the ice that forms is mostly water. Remove the ice, and the remaining liquid is more concentrated. Repeat.
• Do not attempt to distill acetic acid without proper equipment — the fumes are extremely irritating.

Mineral Acids (Advanced)

These are powerful chemicals that enable metal refining, explosives production, and electrochemistry. Handle with extreme caution.

Sulfuric Acid (Oil of Vitriol)

The most important industrial acid. Two methods:

Method 1: From Green Vitriol (Iron Sulfate)

1. Collect green vitriol (iron sulfate crystals — found as mineral deposits near iron pyrite, or made by dissolving iron in dilute sulfuric acid)
2. Heat strongly in a clay retort (distillation vessel)
3. Sulfuric acid distills off as fumes and condenses in a receiver
4. This produces small quantities but requires no complex infrastructure

Method 2: Lead Chamber Process (Simplified)

1. Burn sulfur in air to produce sulfur dioxide (SO2)
2. Pass the SO2 into a lead-lined chamber (lead resists acid)
3. Add water vapor and a small amount of nitric acid (as catalyst)
4. Sulfuric acid condenses on the chamber walls and is collected
5. This is an industrial-scale process — it was the backbone of 18th-century chemistry

Property	Sulfuric Acid
Concentration	30-98% depending on method
Color	Colorless to light brown
Hazard	Severe burns, dehydrates organic matter
Storage	Glass or lead-lined ceramic
Uses	Metal refining, fertilizer, battery acid, making other acids

Sulfuric Acid Is Uniquely Dangerous

Concentrated sulfuric acid generates intense heat when mixed with water. ALWAYS add acid to water, never water to acid. Adding water to acid causes violent boiling and spattering. This rule could save your life.

Hydrochloric Acid (Muriatic Acid / Spirit of Salt)

1. Place common salt in a glass or ceramic retort
2. Add sulfuric acid
3. Heat gently — hydrochloric acid gas evolves
4. Bubble the gas through water to dissolve it (the water becomes hydrochloric acid)
5. The residue in the retort is sodium sulfate (useful for glass making)

NaCl + H2SO4 → NaHSO4 + HCl↑
salt + sulfuric acid → sodium sulfate + hydrochloric acid (gas)

Nitric Acid (Aqua Fortis)

1. Mix saltpeter (potassium nitrate) with sulfuric acid in a glass retort
2. Heat gently — nitric acid fumes evolve
3. Condense in a cooled glass receiver
4. The residue is potassium sulfate (a fertilizer)

KNO3 + H2SO4 → KHSO4 + HNO3↑
saltpeter + sulfuric acid → potassium sulfate + nitric acid (gas)

Nitric acid dissolves copper and silver (not gold), making it essential for metal refining and testing. Mix with hydrochloric acid (3:1 HCl:HNO3) to make aqua regia, which dissolves gold.

Neutralization Reactions

When you combine an acid and a base in the right proportions, you get a neutral salt and water. This is useful for:

Reaction	Product (Salt)	Use
Vinegar + baking soda	Sodium acetate	Mild preservative
HCl + lye (NaOH)	Common salt (NaCl)	Seasoning, preservation
Sulfuric acid + lime	Calcium sulfate (gypsum)	Plaster, construction
Nitric acid + potash	Potassium nitrate (saltpeter)	Gunpowder, fertilizer

Testing for Complete Neutralization

1. Add your indicator to the solution
2. Add acid or base dropwise, stirring after each addition
3. When the indicator shows pH 7 (purple for cabbage indicator), stop
4. The solution is now neutral — evaporate to collect the salt

Safety and Storage

Essential Safety Rules

1. Always add acid to water, never water to acid
2. Wear eye protection — even splashes of weak acids cause eye damage
3. Work outdoors or in well-ventilated areas — many reactions produce toxic fumes
4. Keep water nearby — for flushing skin and eyes immediately after contact
5. Label everything — clearly mark every container with contents and hazard level
6. Never store acids and bases together — leaks could cause violent reactions
7. Use glass, ceramic, or wood containers — acids dissolve metals, bases dissolve aluminum

First Aid for Chemical Burns

Chemical	Immediate Action
Acid on skin	Flush with large amounts of water for 15+ minutes
Base on skin	Flush with water, then rinse with dilute vinegar
Acid in eyes	Flush with clean water for 20+ minutes, seek help
Acid swallowed	Do NOT induce vomiting. Drink milk or water. Seek help

Storage Containers

Material	Suitable For
Glass	All acids and bases (best choice)
Fired ceramic (glazed)	Most acids and bases
Wood	Weak bases (lime water, lye)
Lead	Sulfuric acid
Iron/steel	Concentrated sulfuric acid (forms protective layer)
Copper/brass	NOTHING acidic — dissolves immediately

Glass Is King

If you can produce glass (see Glassmaking), prioritize making bottles and flasks for chemical storage. Glass resists virtually all acids and bases at room temperature. Label with scratched markings that cannot wash off.

What’s Next

With acids and alkalis mastered, you unlock the next tier of chemical technology:

• Gunpowder — requires saltpeter (potassium nitrate), produced from nitric acid and potash
• Antibiotics — acid-base chemistry is fundamental to pharmaceutical extraction
• Electrochemistry — sulfuric acid is the electrolyte in lead-acid batteries, the simplest rechargeable power source

Acids and Alkalis — At a Glance

pH scale: 0 (strong acid) to 14 (strong base), 7 is neutral Best indicator: Red cabbage juice — red in acid, purple at neutral, green in base Lye: Leach hardwood ash with water. Test with egg float. Caustic soda = lime water + soda ash Soda ash: Burn seaweed, dissolve ash, evaporate. Or find natron mineral deposits Vinegar: Ferment sugar to alcohol, then expose to air with Acetobacter for 2-6 weeks Sulfuric acid: Heat green vitriol, or burn sulfur in lead chamber with water and catalyst Hydrochloric acid: Salt + sulfuric acid, heat, bubble gas through water Nitric acid: Saltpeter + sulfuric acid, heat, condense fumes Safety: Always acid to water. Eye protection. Glass containers. Label everything. Neutralization: Acid + base = salt + water. Use indicator to find endpoint.