Why a receiving SOP matters for corrosive liquids
When a tanker, isotank, or IBC load of corrosive liquid arrives from an overseas supplier, the moment you sign the delivery note you take on two separate liabilities: the physical hazard of the material and the commercial risk that what you received does not match what you paid for. For receiving teams, plant QA, and import coordinators, a written standard operating procedure (SOP) closes both gaps. It defines who samples, how they sample safely, which certificate-of-analysis (COA) parameters get cross-checked, and what evidence is needed before acceptance is logged.
This guide covers three common corrosive liquids and the differences that change how you handle each one:
- **Sulfuric acid** (H2SO4) at 50%, 70%, and 98% strengths, UN1830, molar mass 98.08 g/mol.
- **Hydrochloric acid** (HCl) at 25%, 31%, and 36-38% strengths, UN1789, molar mass 36.46 g/mol.
- **Ammonia solution** (NH3.H2O) at 20%, 25%, and 28% industrial strengths, shipped as UN2672 in the 20-28% range, with higher-strength grades falling under UN2073 or UN3318; molar mass 35.046 g/mol, with ammonia boiling near 38 C.
The goal is not to re-run the supplier's laboratory. It is to confirm, with a fast and defensible check, that the delivered active strength and the dangerous-goods documentation match the certificate so your dosing and active-basis cost calculations hold.
Prepare before the truck arrives
Documents to have in hand
Before sampling, the import coordinator should assemble the purchase order, the sales contract and its acceptance clauses, the supplier COA for the exact batch or lot, the dangerous-goods transport paperwork, and the safety data sheet. Line these up so the receiving inspector can compare the claimed grade and concentration on paper before touching the product.
PPE and containment
Each of these liquids attacks skin, eyes, and the respiratory tract. The sampling station needs acid-resistant gloves and apron, chemical splash goggles with a face shield, and an eyewash and safety shower within reach. Concentrated sulfuric acid reacts violently with water and releases heat; hydrochloric acid gives off corrosive mist; ammonia solution releases pungent, irritating vapor. Ammonia sampling in particular should be done outdoors or under local exhaust ventilation, with a suitable respirator available.
Equipment
Standardize on a calibrated hydrometer or density meter for specific gravity, a thermometer because density is temperature-dependent, clean dedicated sampling thieves or bottom-valve sample containers, labeled sample bottles, and a titration kit with standardized titrant. Keep acid and base glassware separate to avoid cross-contamination.
Safe sampling, liquid by liquid
Sulfuric acid (UN1830)
Sample from a representative point, typically a bottom valve or a sealed top sampling port, after confirming the line is depressurized. Draw slowly to avoid splashing. For 98% material, never add the acid to water during dilution for titration; add acid to water in small amounts with cooling. Record the sample temperature immediately, since sulfuric acid density shifts measurably with temperature and with concentration.
Hydrochloric acid (UN1789)
Open ports carefully because headspace can hold hydrogen chloride mist. Sample downwind, let the initial vapor clear, and cap the sample bottle quickly to limit HCl loss. Fuming is more pronounced at the 36-38% end of the range, so a tightly sealed bottle protects your titration result.
Ammonia solution (UN2672, UN2073, UN3318)
Ammonia is the sampling challenge of the three. Because ammonia is volatile and boils near 38 C, dissolved gas escapes from warm product and from any opened headspace, so a sample that sits open will read weaker than the bulk. Chill the sample where practical, fill the bottle to minimize headspace, cap immediately, and test promptly. This is why strength-at-receipt can legitimately read below strength-at-dispatch even when the supplier shipped on-spec material. Your SOP should state the acceptable temperature and handling window so a warm, vented sample is not mistaken for an under-strength delivery.
COA parameters to cross-check
For every lot, compare the COA against the contract grade and against your own quick checks. At minimum verify:
- **Assay / active concentration** (percent H2SO4, HCl, or NH3) against the ordered strength.
- **Specific gravity or density** at the stated reference temperature.
- **Appearance and color**, which can flag iron pickup or contamination.
- **Key impurities** named in the contract, such as iron, chloride, sulfate, or heavy metals, depending on grade.
- **Lot or batch number** matching the drum, IBC, or tank car markings.
If the COA omits a parameter your contract requires, that is a documentation gap to raise before acceptance, not something to assume.
The specific-gravity and titration cross-check
Two fast lab checks confirm that delivered active strength matches the certificate.
Step 1: specific gravity
Measure density at a controlled temperature and compare it to published concentration-versus-density references for each acid or for ammonia solution. Specific gravity gives a quick, non-destructive estimate of concentration and is a good screen. Because density changes with temperature, always record the measurement temperature and correct to the reference basis your SOP uses. A density well outside the expected band for the ordered strength is an immediate signal to investigate before anything is unloaded into storage.
Step 2: acid-base titration
Specific gravity alone cannot distinguish a genuine strength difference from a contaminant that shifts density, so confirm active strength by titration. Titrate the acids against a standardized base to a suitable endpoint and calculate percent acid using the molar masses above (98.08 g/mol for H2SO4, 36.46 g/mol for HCl). Titrate ammonia solution against a standardized acid using 35.046 g/mol for NH3. The titration gives the true active-basis strength, which is what your dosing rate and your cost per kilogram of active ingredient depend on. If you buy on an active basis, a one- or two-point concentration shortfall changes both the chemistry and the price you should pay.
Reconciling the two
When specific gravity and titration agree with each other and with the COA, you have a strong, defensible acceptance record. When they disagree, treat it as a flag: re-sample, check sample temperature and handling, and for ammonia confirm the sample was not vented. Document which method governs under your contract.
Verify dangerous-goods identity and labeling
Concentration verification is only half the job. The transport identity must also match the actual product. On arrival, confirm that the UN number, proper shipping name, and package labeling agree with both the measured concentration and the dangerous-goods paperwork:
- Sulfuric acid should carry **UN1830** with the correct shipping name and corrosive labeling.
- Hydrochloric acid should carry **UN1789**.
- Ammonia solution at 20-28% should carry **UN2672**, while stronger ammonia grades move under **UN2073** or **UN3318**, which carry different hazard classifications.
A mismatch, for example an ammonia strength that does not fit its declared UN number, is a compliance problem that can stall customs clearance and create safety and insurance exposure. The import coordinator should treat any labeling or paperwork discrepancy as a hold condition and escalate before product is accepted into the plant.
For teams that want reference specifications to compare against incoming lots, product pages such as those from a sulfuric acid supplier list typical grades and strengths you can line up against the COA and the drum markings.
Document accept, reject, and conditional decisions
The receiving-inspection record is the evidence that ties your tests to the contract. For each lot, capture the lot number, sampling time and conditions, measured specific gravity and temperature, titration result and calculated active strength, the COA values compared against them, the dangerous-goods identity check, and the inspector's signature.
Then record the decision explicitly:
- **Accept** when strength, density, impurities, and transport identity all meet contract terms.
- **Reject** when a parameter fails and the contract allows rejection; quarantine the material and notify the supplier.
- **Conditional acceptance** when, for example, ammonia reads slightly low but handling suggests venting; re-sample under controlled conditions before final sign-off.
Tie each decision to the specific acceptance clause in the sales contract so the commercial consequence, whether full payment, price adjustment on an active basis, or return, is unambiguous. When you source from a hydrochloric acid supplier, clear acceptance terms agreed up front make these decisions faster and less contentious.
Using China's 2025 import figures as a sanity check only
Public trade data can give receiving and procurement teams a directional feel for liquidity and grade mix, but it must never be used as a firm price or quality benchmark for a specific lot. According to UN Comtrade public statistics for 2025, China's reported imports were roughly 126.2 million kg of sulfuric acid (HS 280700) valued near USD 15.5 million, about 8.1 million kg of hydrochloric acid (HS 280610) valued near USD 14.6 million, and about 348.5 million kg of anhydrous ammonia (HS 281410) valued near USD 133.0 million.
Read these only as context. The large reported ammonia volume and value, for instance, tells you the ammonia trade is liquid and actively moving, which is a reassuring backdrop when you are planning a purchase of ammonia solution. It does not tell you the concentration, impurity profile, or price of your particular shipment. Note too that HS 281410 covers anhydrous ammonia rather than the aqueous solution grades you receive, so the figure is a market-liquidity indicator, not a like-for-like benchmark for your product. Firm price and quality still come from your contract, the supplier COA, and your own verified test results, in that order.
Putting the SOP into daily practice
A workable receiving SOP for corrosive liquids is short enough to follow under time pressure and strict enough to protect people and margin. Standardize the PPE and sampling method per product, screen with specific gravity, confirm with titration on an active basis, verify UN number and labeling against the actual concentration, and record an explicit accept or reject decision tied to the contract. Handle ammonia with extra care for volatility and headspace so a vented sample never triggers a false rejection. Used this way, the procedure gives receiving teams, plant QA, and import coordinators a defensible, repeatable basis for signing off acceptance, and it keeps your dosing and cost calculations anchored to what you actually received.
Sources
- UN Comtrade public trade statistics, China imports of sulfuric acid (HS 280700), 2025: https://comtradeapi.un.org/public/v1/preview/C/A/HS?reporterCode=156&period=2025&cmdCode=280700&flowCode=M&partnerCode=0&partner2Code=0&customsCode=C00&motCode=0&maxRecords=1
- UN Comtrade public trade statistics, China imports of hydrochloric acid (HS 280610), 2025: https://comtradeapi.un.org/public/v1/preview/C/A/HS?reporterCode=156&period=2025&cmdCode=280610&flowCode=M&partnerCode=0&partner2Code=0&customsCode=C00&motCode=0&maxRecords=1
- UN Comtrade public trade statistics, China imports of anhydrous ammonia (HS 281410), 2025: https://comtradeapi.un.org/public/v1/preview/C/A/HS?reporterCode=156&period=2025&cmdCode=281410&flowCode=M&partnerCode=0&partner2Code=0&customsCode=C00&motCode=0&maxRecords=1
