Summary. A kilogram of 35% hydrochloric acid holds 350 g of HCl and a kilogram of 30% holds 300 g, about 1.17 times as much. Quotes are only comparable once strength, unit, pack and paperwork are on the same basis. The conversions below are general knowledge, not an SPC specification.
Indian buyers ask for hydrochloric acid (HCl, CAS 7647-01-0) by percentage: 30%, 33%, 35%, sometimes a range or just 'commercial'. The numbers look close, yet they change how much active acid arrives. This guide covers only how to compare and convert quotes. For grades, packs, documents, storage and safety, see the hydrochloric acid (HCl) product page. Supreme Petro Chemicals is a Chennai trader and bulk distributor, not a manufacturer.
Why are 30%, 33% and 35% quotes not for the same quantity of acid?
The percentage is the weight of hydrogen chloride in 100 parts by weight of solution (% w/w); the rest is water. A kilogram of 30% acid carries 300 g of HCl, a kilogram of 35% carries 350 g. A lower rate per kilogram for 30% material is therefore not necessarily lower per kilogram of HCl.
There is a second trap: some suppliers and some labels quote strength as % w/v (grams of HCl per 100 mL) rather than % w/w. Because the solution is denser than water, the two figures differ. A quote that does not say which one it means cannot be compared with one that does.
What do 30%, 33%, 35% and 37% look like side by side?
Density rises with strength, so a litre of stronger acid also weighs more and holds more HCl. Approximate values at 20 C from standard tables (general knowledge, not an SPC specification; the density of your delivery is a batch measurement). SPC lists 30%, 33% and 35% grades; 37% is shown only because it is the top of the concentrated band in product data and the figure most people have in mind as 'fuming' acid.
| HCl % w/w | Approx. density (g/mL) | HCl per kg of solution (g) | HCl per litre (g) | Approx. molarity (mol/L) |
|---|---|---|---|---|
| 30 | 1.149 | 300 | 345 | 9.5 |
| 33 | 1.164 | 330 | 384 | 10.5 |
| 35 | 1.174 | 350 | 411 | 11.3 |
| 37 | 1.184 | 370 | 438 | 12.0 |
How do you convert litres to kilograms to kilograms of HCl?
Quotes arrive in mixed units: per kilogram, per litre, per carboy, per barrel. The walk-through is always the same three steps: litres to kilograms of solution (multiply by density), kilograms of solution to kilograms of HCl (multiply by the percentage), then compare on kilograms of HCl.
| Case | Step 1: kg of solution | Step 2: kg of HCl |
|---|---|---|
| 200 L of 35% acid | 200 x 1.174 = about 235 kg | 235 x 0.35 = about 82 kg |
| 1000 L of 30% acid | 1000 x 1.149 = about 1149 kg | 1149 x 0.30 = about 345 kg |
| 35 kg of 33% acid | 35 kg as stated | 35 x 0.33 = about 11.6 kg |
To compare two offers, put the strength side by side first: a 35% acid carries more HCl per kilogram than a 30% acid, so offers at different strengths are not like-for-like until the strength and basis are stated.
How do you dilute strong acid to a working strength?
Many users buy strong acid and dilute on site. The arithmetic is mass balance: HCl in the strong acid equals HCl in the diluted acid. Total mass of the diluted acid equals the HCl mass divided by the target fraction; the water to add is the difference. These are general-knowledge examples for 1 kg of starting acid, using mass rather than volume so density does not enter.
| Start | Target | HCl in 1 kg | Total mass at target | Water to add |
|---|---|---|---|---|
| 35% | 10% | 350 g | 3.5 kg | 2.5 kg |
| 33% | 5% | 330 g | 6.6 kg | 5.6 kg |
| 30% | 15% | 300 g | 2.0 kg | 1.0 kg |
| 30% | 10% | 300 g | 3.0 kg | 2.0 kg |
Always add the acid to the water, never the water to the acid, because dilution releases heat. Wear acid-resistant PPE, dilute in a ventilated area and use compatible vessels. For process baths, use the strength and make-up procedure your own process specification states. Note that a stronger starting acid does not mean a better bath; it means fewer containers for the same amount of HCl, which is exactly why the like-for-like comparison above matters.
What are synthetic and by-product hydrochloric acid?
General knowledge: synthetic acid is made by burning hydrogen in chlorine and absorbing the gas in water; by-product acid is recovered from other chlorination processes and may carry traces of organic compounds. 'Synthetic (35%)' is the grade name in SPC product data. If your process is sensitive to trace organics or colour, ask which route a batch follows.
A quote checklist you can paste into your enquiry
- Strength: the percentage and whether it is % w/w or % w/v.
- Unit: kilograms, litres or packs, and the density assumed if litres are used.
- Pack: 35 kg carboy, 200 L barrel, 1000 L IBC or bulk tanker, as listed in SPC product data.
- Standard and edition: if your purchase specification names one, say which; do not assume it.
- Certificate of Analysis parameters: list the ones you need, such as total acidity as HCl, specific gravity, and free chlorine and bromine. The commercial-grade TDS reports those for one reference lot; it is not a limit for every grade.
- Receiving arrangement: tank, unloading method and who accepts the delivery.
Can hydrochloric acid quotes be compared with sulphuric or nitric acid quotes?
Not on price per kilogram, and often not at all. General knowledge: on a 100% basis, a kilogram of hydrogen chloride supplies about 27.4 mol of hydrogen ions, a kilogram of sulphuric acid about 20.4 mol (two per molecule) and a kilogram of nitric acid about 15.9 mol. The acids are also not interchangeable chemically. Nitric acid is a strong oxidiser, sulphuric acid pickling is usually run hot, and hydrochloric acid adds chloride to the process. If you are weighing the three for a pickling or cleaning line, read the sulphuric acid and nitric acid product pages alongside the hydrochloric acid page and decide on process fit first, then compare quotes within the chosen acid.
Ready to compare?
Send the strength, pack, quantity and delivery point to Sanketh on WhatsApp at +91 86087 80096 or via the contact page; we quote within 4 working hours, and a batch Certificate of Analysis is supplied with every delivery. If you buy several acids, the acid supplier guide for sulphuric, nitric and hydrochloric acid covers them together.
FAQ
Is muriatic acid stronger than hydrochloric acid?
No. Muriatic acid is the same chemical, CAS 7647-01-0. The strength printed on a muriatic acid label varies between products, so ask for the percentage HCl rather than relying on the name.
Can I compare a 30% quote and a 35% quote by rate per kilogram alone?
No. A kilogram of 35% holds about 1.17 times the HCl of a kilogram of 30%. Convert each quote to HCl content first using the worksheet above, and check the units and the pack.
Does a higher percentage always mean a better grade?
No. Strength and grade are different questions. SPC lists Commercial 30%, Technical 33% and Synthetic 35%, all industrial grades; none is food or pharma grade. Choose the strength your process needs and ask for the Certificate of Analysis parameters that matter to you.