The pH value of a substance represents a quantitative measure of its acidity or alkalinity, calculated as the negative logarithm of the hydrogen ion concentration:
Fact-Sheet of pH Values for Common Everyday Substances
The following comprehensive table lists the typical pH values of substances encountered in daily life, ranging from highly industrial inputs to household items and biological fluids.
| Substance Category | Common Name / Substance | Typical pH Value | Exact Chemical Nature |
| Industrial / Automotive | Battery Acid (33% H2SO4) | ~0.5 | Strongly Acidic |
| Biological Fluids | Gastric Juice (Stomach Acid) | 1.5 – 3.0 | Strongly Acidic |
| Beverages & Food | Lemon Juice | 2.2 – 2.4 | Moderately Acidic |
| Beverages & Food | Vinegar (4-8% Acetic Acid) | 2.5 – 3.0 | Moderately Acidic |
| Beverages & Food | Carbonated Soft Drinks / Colas | 2.5 – 3.2 | Moderately Acidic |
| Beverages & Food | Orange Juice | 3.5 – 4.0 | Moderately Acidic |
| Beverages & Food | Tomato Juice | 4.1 – 4.4 | Weakly Acidic |
| Beverages & Food | Black Coffee | 5.0 | Weakly Acidic |
| Environmental | Acid Rain | < 5.6 | Weakly Acidic |
| Beverages & Food | Cow’s Milk | 6.5 – 6.7 | Near Neutral |
| Biological Fluids | Human Saliva (Before Meals) | 6.5 – 7.0 | Near Neutral |
| Environmental | Pure Distilled Water | 7.0 | Neutral |
| Biological Fluids | Human Tears | 7.4 | Near Neutral |
| Biological Fluids | Human Blood | 7.35 – 7.45 | Weakly Alkaline |
| Environmental | Sea Water | 8.1 – 8.3 | Weakly Alkaline |
| Household / Medical | Baking Soda Solution (NaHCO3) | 8.3 – 8.5 | Weakly Alkaline |
| Household / Medical | Milk of Magnesia [Mg(OH)2] | 10.5 | Moderately Alkaline |
| Household / Cleaning | Household Ammonia Solution | 11.0 – 11.5 | Strongly Alkaline |
| Household / Cleaning | Laundry Detergent Liquid | 11.5 – 12.0 | Strongly Alkaline |
| Household / Cleaning | Liquid Bleach (Sodium Hypochlorite) | 12.5 | Strongly Alkaline |
| Household / Cleaning | Drain Cleaner (Sodium Hydroxide) | 13.0 – 14.0 | Strongly Alkaline |
Detailed Profile of Key Acidic Everyday Substances
Gastric Juice (pH 1.5 – 3.0)
The human stomach lining secretes highly concentrated hydrochloric acid (HCl). This intense acidity is mandatory for survival because it denatures dietary proteins, activates the proteolytic enzyme pepsin, and acts as a primary chemical barrier against ingested microbial pathogens.
Vinegar and Citrus Juices (pH 2.0 – 3.0)
- Vinegar: Contains acetic acid (CH3COOH). Its low pH prevents the growth of food-spoiling bacteria, making it an exceptional natural preservative for pickling.
- Lemon and Lime Juices: Rich in citric acid (C6H8O7). The high concentration of hydrogen ions creates the characteristic sour taste detected by the human gustatory system.
Carbonated Drinks and Soft Drinks (pH 2.5 – 3.2)
Commercial carbonated beverages are acidic due to the presence of dissolved carbon dioxide gas (CO2), which forms carbonic acid (H2CO3). Additionally, manufacturers add phosphoric acid (H3PO4) to colas to impart a sharp, tangy flavor and inhibit the growth of molds and bacteria in high-sugar environments.
Detailed Profile of Key Neutral and Biological Substances
Pure Water (pH 7.0)
Pure distilled water at 25°C undergo self-ionization to yield an equal concentration of hydrogen (H^+) and hydroxyl (OH^-) ions (1.0 × 10-7 mol/L each). This balance forms the exact neutral anchor point of the pH scale.
Human Blood (pH 7.35 – 7.45)
Human blood is strictly maintained within a narrow, slightly alkaline range. Even a minor deviation below 7.35 (acidosis) or above 7.45 (alkalosis) can disrupt cellular machinery, enzyme functions, and oxygen transport, leading to severe physiological shock or organ failure. The body utilizes the bicarbonate-carbonic acid buffer system (HCO3^- / H2CO3) to maintain this precise equilibrium.
Detailed Profile of Key Basic Everyday Substances
Milk of Magnesia (pH 10.5)
An aqueous suspension of magnesium hydroxide [Mg(OH)2]. Because it is a weak and relatively insoluble base, it does not damage oral or esophageal tissues. When swallowed, it safely neutralizes excess stomach acid (HCl) via a standard neutralization reaction:
Household Cleaning Solutions (pH 11.0 – 14.0)
- Ammonia & Detergents: Possess high pH levels to emulsify, hydrolyze, and break down organic fats, grease, and oils into soluble fatty acids, facilitating easy removal from surfaces and fabrics.
- Drain Cleaners: Formulated with concentrated sodium hydroxide (NaOH). This strong alkali generates an intensely basic solution (pH 14) that can chemically dissolve hair, grease, and organic blockages inside plumbing networks through alkaline hydrolysis.