Ammonium bifluoride: buy the identity, read the safety data sheet

One salt, and a great many retired numbers

Ammonium bifluoride is NH₄HF₂, the acid salt of ammonium fluoride and hydrogen fluoride, and the aggregated public record gives its current CAS number as 1341-49-7 with two related parent registrations — 12125-01-8 for ammonium fluoride and 7664-39-3 for hydrogen fluoride. What is unusual about the record is the list beneath that: twelve deprecated CAS numbers, among them 7790-15-0, 16941-26-7 and 14055-61-9. A specification, a legacy purchase order or an old data sheet may perfectly well carry one of those. Matching on a retired number is how two parties end up believing they have agreed on a substance.

The commercial article is not the pure compound either, and the record says so from two directions. It describes the material as “available as flakes, granules, and solutions” with “impurities at <1% include hydrogen fluoride and ammonium fluoride,” and separately records that “commercial ammonium bifluoride, which usually contains 1% NH₄F, is made by gas phase reactions of one mole of anhydrous ammonia with two moles of anhydrous hydrogen fluoride; the melt that forms is flaked on a cooled drum.” It lists grades as “Pure, 99+%; Technical, 97-98.5%.” Assay, the identity of the balance, and the physical form are therefore three separate questions, and a flake is not a granule for a dissolving or dosing arrangement.

In water it is hydrofluoric acid chemistry

The record is direct about what happens when the salt meets water: “dissolves in water and forms a weak solution of hydrofluoric acid.” It is equally direct about acid contact — the material “reacts with concentrated acids (formation of HF) and concentrated alkaline solutions (formation of NH₃)” — and about silicates, reacting “with silicon containing materials like glass or ceramics at room temperature (formation of SiF₄).” Two independent entries add that in the presence of moisture it “will corrode glass, cement, and most metals,” and that it will etch glass. The salt is a solid, it is recorded as non-combustible, and none of that makes it inert.

Those statements are why the packaging and transfer fields on a purchase record are not administrative here. The record carries an explicit container instruction attributed to the US Coast Guard: “do not use steel, nickel, or aluminum containers,” with the note that flammable hydrogen gas may collect in enclosed spaces. It records the material as deliquescent and “hygroscopic if ambient humidity over 50%” with “no tendency to form hydrates,” which makes ambient humidity at the storage location a real variable for a flake. It also shows why a number needs its originating record: decomposition is given as 240 °C in one entry and, from a different agency, as a boiling point of 463.1 °F that “decomposes at 446 °F,” which is about 230 °C. Those do not agree, and neither was measured on a supplied lot.

This guide does not tell anyone how to use this material. It sets no dose, ratio, dissolving procedure, temperature or endpoint, specifies no personal protective equipment, and gives no first-aid or medical guidance. The safety data sheet for the exact product, at its current revision, governs handling, storage, spill response and emergency planning, and it is the document to obtain and read before the material is ordered rather than after it arrives.

The exposure evidence has to be assembled

Queried on September 12, 2026, the NIOSH Pocket Guide had no card for ammonium bifluoride. The nearest entry is hydrogen fluoride, CAS 7664-39-3, which gives a NIOSH REL of 3 ppm as a time-weighted average with a 6 ppm ceiling over 15 minutes, an IDLH of 30 ppm, and a conversion of 1 ppm = 0.82 mg/m³. Its incompatibilities are recorded as “metals, water or steam,” with the note that hydrogen fluoride is “corrosive to metals” and “will attack glass and concrete.”

The gap is the finding. Hydrogen fluoride is a gas or a fuming liquid below 67 °F and ammonium bifluoride is a crystalline solid; the exposure routes, the airborne form and the sampling method are not the same problem, so the HF card cannot simply be applied to the salt. What it does establish is the severity of the fluoride hazard that the salt can generate, and that an exposure assessment for an operation using the salt has to be built for that operation rather than looked up. That assessment is the employer’s, performed by a qualified person for the actual task, and no purchase document or supplier statement can stand in for it.

A limit expressed “as F” is not a limit on the salt

The OSHA air-contaminant tables carry several entries a fluoride operation will meet, and they are not interchangeable. Table Z-1 of 29 CFR 1910.1000 lists “Fluorides (as F)” with 2.5 in the mg/m³ column and, in the ppm column, footnote 4 — which reads, in full, “Varies with compound.” The table is stating outright that a parts-per-million figure cannot be given for this row, because a fixed mass of fluorine sits in a different mass of every compound that carries it. Separately, Table Z-1 lists “Hydrogen fluoride (as F)” under CAS 7664-39-3 with footnote 2, “See Table Z-2,” and Table Z-2 gives hydrogen fluoride 3 ppm and “Fluoride as dust” 2.5 mg/m³. Both Table Z-2 entries are annotated “(Z37.28-1969)” — the limits are pinned to a consensus standard from 1969, the same pattern of a rule adopting a private document at a fixed edition that runs through this whole collection.

So read the units before comparing anything. A limit expressed “as F” is a limit on the fluorine content of the airborne material, not on the mass of the salt; 2.5 mg/m³ as F and 2.5 mg/m³ of ammonium bifluoride are different quantities. A row is also keyed to a substance and a CAS number, and a similar common name is not the same row — the same trap the aerospace materials and cleanliness collection documents for naphtha. Which row governs a given operation, and what obligation follows, is the employer’s determination, made with a qualified industrial hygienist and an assessment of the actual task. Table Z-1’s own note records that a CAS number there “is for information only” and that “enforcement is based on the substance name.”

What to put on the purchase document

Write the identity first: the current CAS number, the formula, the form as delivered, and the assay with the identity of the balance. Then the attributes your process actually controls, each with a limit, a method, units and a reporting limit taken from your own specification rather than from a supplier’s marketing sheet. Then the packaging and transfer interface, with the wetted materials named, since the record rules out several obvious ones. Then the documents: the safety data sheet at its current revision, and the lot documentation. Alliance sends a Certificate of Analysis when a customer asks, at no charge; say in the purchase order which analytes and methods it must cover, and note that a sample certificate describes what the product has generally looked like while a lot certificate reports results for the material being shipped.

The aggregated record lists oil well acidizing among this substance’s industrial uses, alongside glass etching, electroplating, metal brightening and equipment cleaning. That is a statement about what the chemical industry does with the compound, recorded by a public agency. It is not a statement about any Alliance product, and nothing in this library says that an Alliance product is suitable, approved or recommended for well service or for any other application. This is source-based editorial guidance, no original testing was performed for it, and independent specialist review is pending.

• Is the CAS number on the specification the current registration, or one of the deprecated numbers?
• What is the assay, what is the balance, and is the material a flake, a granule or a solution?
• Which wetted materials contact it, and does the arrangement avoid the containers the record rules out?
• Who holds the current safety data sheet, and who owns the exposure assessment and emergency planning for this operation?

Requirement → evidence → decision boundary

An editorial checklist for your review—not a table of product specifications.

Revision record

1.0 · September 12, 2026 — Source-based editorial edition. No original testing or product qualification is claimed.

For operators, service companies and their purchasing teams buying fuels, acids, glycols and light hydrocarbon cuts. This collection does not design or select a well treatment, set a dose, rate or blend, classify a delivered material, specify personal protective equipment, or make a discharge, permit or waste determination.