How to Choose the Right Acid Concentration for Your Application
One of the most common questions we get from customers is: “What concentration of nitric acid do I need?” It’s a great question — and the answer depends entirely on your application. Using the wrong concentration can mean poor results, wasted material, or unnecessary safety risk.
This guide breaks down the most common nitric acid concentrations and which applications each is best suited for.
Nitric Acid Concentration Overview
| Concentration | Common Name | Primary Uses |
|---|---|---|
| 20–30% | Dilute nitric acid | Mild metal cleaning, educational labs, some pH adjustment |
| 52–68% | Concentrated nitric acid (lab/tech grade) | Gold refining, metal etching, sample digestion, industrial processes |
| 67–68% | 42° Baumé — the industry standard | Aqua regia, passivation, analytical chemistry, urban mining |
| 90%+ | Fuming nitric acid (red or white) | Rocket propellant, specialized synthesis — extremely hazardous |
When to Use 67% Nitric Acid
67% is the most versatile and widely used concentration for industrial and laboratory applications. It’s the standard for:
Gold Refining & Aqua Regia
The aqua regia process requires concentrated nitric acid — 67% is the industry standard. Dilute acid won’t generate sufficient oxidizing power to dissolve gold effectively. If you’re refining gold, recovering precious metals from e-waste, or doing parting work, 67% is what you need.
🔗 Shop Nitric Acid 67% Lab Grade →
Stainless Steel Passivation
Passivation specifications (ASTM A967, AMS 2700) typically call for 20–50% nitric acid solutions. However, 67% is commonly diluted on-site to the required working concentration, giving you flexibility across multiple passivation specs.
Laboratory Sample Digestion
Analytical labs use concentrated nitric acid (67–70%) for microwave-assisted and open-vessel digestion of environmental, biological, and materials samples. The high concentration ensures complete oxidation of organic matter before ICP or AA analysis.
Metal Etching
Copper, brass, and bronze etching for PCB manufacturing and decorative metalwork typically uses diluted nitric acid (10–30%). Starting with 67% and diluting gives you precise control over etch rate and surface finish.
When Dilute Acid Is Sufficient
For some applications, concentrated acid is overkill — and more hazardous than necessary:
- Educational demonstrations: 10–20% solutions are safer for classroom use
- Light metal cleaning: Dilute acid removes surface oxides without aggressive attack
- pH adjustment in small systems: Highly diluted acid (1–5%) is easier to dose accurately
In these cases, you can dilute 67% nitric acid with distilled water to your target concentration. Always add acid to water — never water to acid.
When You Need Fuming Nitric Acid (90%+)
Fuming nitric acid (red fuming or white fuming) is used in highly specialized applications: rocket propellant oxidizers, certain nitration reactions in pharmaceutical synthesis, and military/aerospace applications. It is extraordinarily hazardous and subject to strict regulatory controls. For the vast majority of industrial and laboratory users, 67% is the correct choice.
Grade Matters Too: Lab vs. Technical vs. Reagent
- Technical/Lab Grade (our stock): High purity suitable for most industrial and laboratory applications. Includes a Certificate of Analysis. Ideal for gold refining, metal processing, and general lab use.
- ACS Reagent Grade: Meets American Chemical Society purity standards. Required for some analytical methods where trace metal contamination must be minimized.
- Electronic Grade: Ultra-high purity for semiconductor fabrication. Typically not needed outside of chip manufacturing.
For gold refining, metal etching, passivation, and most lab applications, lab/technical grade 67% is the right choice — and significantly more cost-effective than reagent grade.
Size Guide: How Much Do You Need?
- Hobbyist / occasional use: Start with a quart. A quart of 67% nitric acid goes a long way for small-batch gold refining or occasional etching.
- Regular refiner or active lab: The 4x Quarts bundle (1 gallon equivalent) offers the best value and ships without a hazmat fee.
- High-volume or commercial: 5-gallon or 55-gallon drum pricing offers significant per-unit savings.
Ready to Order?
Grow It Depot stocks Nitric Acid 67% Lab/Technical Grade with a COA included, shipped in DOT-compliant FLPE bottles from US inventory.