Manufacture of Nitroform and Its Salts (1964)
U.S. Patent No. 3,125,666, granted on March 17, 1964, to a team of chemists including Donald J. Glover, Joseph C. Dacons, and James E. West (assigned to the U.S. Secretary of the Navy), details a revolutionary, safe, and efficient method for producing nitroform (trinitromethane). Nitroform is a critical chemical intermediate used to manufacture high-energy propellants and castable explosives like TNETB, which are significantly more powerful than TNT.
Before this invention, producing nitroform required either extreme industrial conditions (expensive and complex equipment) or hazardous reagents that produced toxic by-products like hydrazoic acid. This patent provided the “Navy method”—a commercially feasible way to turn tetranitromethane into nitroform using low-cost, stable reagents.
The Innovation: The Nitrite Reduction Method
The core of the invention is the discovery that nitrite ions (from simple salts like sodium or potassium nitrite) can efficiently strip a nitro group from tetranitromethane to produce the nitroform anion.
Previously, chemists tried using potassium hydroxide to achieve this, but it often resulted in the tetranitromethane turning into useless carbonate. The inventors discovered that adding a nitrite salt acts as a “selective” agent that speeds up the desired reaction by many orders of magnitude, making the process nearly 100% efficient (quantitative yield).
Why This Process Was Superior
- Safety: It avoids the formation of hazardous alkyl nitrates or toxic gases associated with previous reduction methods.
- Cost-Effective: It uses common, inexpensive chemicals like sodium nitrite and sodium bicarbonate.
- Mild Conditions: The reaction occurs at room temperature or gentle heat (up to 50°C), requiring no specialized high-pressure hardware.
- High Density Explosives: It paved the way for TNETB, which has a 47% higher oxygen density per cubic centimeter than TNT, making it a much more effective underwater and fragmentation explosive.
Key Chemical Components
The process utilizes a synergistic blend of reagents in a mixed solvent:
| Component | Function |
| Tetranitromethane (TNM) | The primary raw material; the precursor to nitroform. |
| Sodium/Potassium Nitrite | The reducing agent that provides the nitrite anion to trigger the reaction. |
| Alkaline Salts (e.g., Bicarbonate) | Used to neutralize acidic by-products and regenerate the nitrite catalyst. |
| Methanol/Water Solvent | A “bridge” solvent that allows the oily TNM to mix and react with the water-soluble salts. |
| Mineral Acid (e.g., HCl) | Used in the final step to convert the nitroform salt into free, liquid nitroform. |
Performance: TNETB vs. TNT
The primary motivation for this process was the production of TNETB (2,2,2-trinitroethyl-4,4,4-trinitrobutyrate). The patent provides a dramatic comparison of the explosive’s performance:
| Metric | TNETB | TNT | Improvement |
| Crystal Density | 1.78 g/cc | 1.65 g/cc | +8% |
| Detonation Velocity | 8,450 m/sec | 7,054 m/sec | +20% |
| Heat of Detonation | 1,524 cal/g | 984 cal/g | +55% |
| Bubble Energy (Underwater) | 1.16 | 1.00 | +16% |
The Manufacturing Process
The Navy chemists outlined a precise “one-pot” method for creating the salt or the free acid:
- Mixing: Combine sodium nitrite and sodium bicarbonate in a 50/50 methanol-water solution.
- Reaction: Add tetranitromethane dropwise while stirring at 50°C. The mixture turns from colorless to red.
- Coalescence: Wait for the multiphase system to become a single, homogeneous liquid (usually within 20–45 minutes).
- Acidification: If free nitroform is desired, add concentrated hydrochloric acid.
- Extraction: Pull the nitroform out of the mixture using a solvent like methylene chloride or chloroform.
About the Inventors
The team comprised prominent researchers for the U.S. Navy, including Donald J. Glover, Joseph C. Dacons, and Mortimer J. Kamlet.
- National Impact: Because the patent was assigned to the Secretary of the Navy, the government could use this high-yield process for military propellants royalty-free.
- Joseph C. Dacons: A highly respected African American chemist at the Naval Ordnance Laboratory, Dacons held multiple patents related to the synthesis of energetic materials and explosives.
- Scientific Legacy: Their work at the Naval Ordnance Laboratory in Maryland helped define the “Golden Age” of energetic materials research, where chemistry was used to significantly boost the range and power of naval weaponry.
Summary of Claims
The patent explicitly protects:
- The process of reacting tetranitromethane with a light metal nitrite salt.
- Maintaining a ratio of at least two equivalents of salt per equivalent of tetranitromethane.
- The use of aqueous alkaline solutions to prevent the decomposition of the resulting nitroform salts.
