MMA-grade ammonium sulphate — a by-product of methyl methacrylate manufacture — is chemically indistinguishable from other ammonium sulphates once applied. What differs in practice is particle size: a uniform medium-to-fine crystal, which changes how the material dissolves, spreads and blends. Route chemistry and full specification are on the MMA ammonium sulphate page.
Substance identity
Ammonium sulfate · (NH₄)₂SO₄ · CAS 7783-20-2 · PubChem CID 6097028 · 132.14 g/mol · white to off-white medium crystals, 0.5–2 mm predominant.
Specification
— typical commercial ranges
| Parameter | Typical range |
|---|---|
| Total nitrogen (N) | 21.0 % min |
| Sulfur (S) | 24 % min |
| Moisture (H₂O) | ≤ 0.3 – 1.0 % |
| Free acid (as H₂SO₄) | ≤ 0.05 – 0.10 % |
| pH, 5 % solution | 5.0 – 6.0 |
| Particle size | 0.5 – 2 mm predominant |
Properties
Medium crystal has a larger specific surface than the coarse caprolactam habit, so it dissolves faster in a dissolving tank and reacts into the soil solution faster after a wetting event. The same property makes it slightly more prone to caking under humid storage and to bridging in hoppers. Nutrient behaviour in soil — ammonium retention on exchange sites, nitrification over weeks, acidification of roughly 5.4 kg CaCO₃ per kg N — is that of ammonium sulphate generally.
Applications
Direct application on sulfur-responsive crops, and dissolving-tank use where rapid, complete dissolution is wanted. Well suited as compaction feed: a uniform fine-to-medium feed compacts more consistently than a wide size distribution, because the roll nip sees a consistent bulk density.
The honest limitation is bulk blending. A 0.5–2 mm crystal blended with 2–4 mm granular DAP, MOP or urea will segregate during loading, transport and spreading, and the field result is banded nutrition that no spreader setting corrects. Either match sizes or specify a compacted granular ammonium sulphate for blending.
Handling and storage
Dry, covered, off the floor; limit stack height because finer crystal cakes more readily. Dust extraction at transfer points. Away from lime, caustic and other alkalis. Do not store pre-mixed with urea — the mixture’s critical relative humidity falls to roughly 56 % at 30 °C.
Notes
Availability of MMA-route material tracks methyl methacrylate production, not fertiliser demand — as with all by-product ammonium sulphate, supply is set by the parent process. Where continuity of a single crystal habit matters to a downstream blending operation, this is worth planning around.