Kjeldahl Digestion & Distillation Unit Lab Equipment Manufacturer, Supplier and Exporter in India

Eight items are listed here, KDDU-0001 to KDDU-0008: digestion units in electric and gas-heated forms, distillation units and assemblies, a combined digestion and distillation unit, a dry block digester and a chemical oxygen demand digestion apparatus. They are not bench instruments. A Kjeldahl determination boils samples in concentrated sulfuric acid and then distils the result from concentrated alkali, so the purchase commits a laboratory to a fume handling arrangement, a bench that resists acid, and a set of rules for the people using it. Settle those before comparing prices.

What is in the range

The fume scrubber is not an accessory

Digesting a sample in hot concentrated sulfuric acid produces a large volume of dense acidic fume. That fume has to be collected and neutralised, and if it is not, it goes into the room and into the building's fabric. So the first question of any digestion unit is what handles the fume:

• Is a scrubber or an exhaust manifold supplied, and what does it use? A water scrubber handles some of it; an alkali scrubber handles more. Ask what the supplier recommends for the number of places you are buying, and get the answer in writing before the order.
• Does the unit go in a fume cupboard, or does it stand on the bench with its own extraction? The two lead to different installations and different costs, and only one of them needs a cupboard big enough to take the unit and the operator's hands.
• What does the exhaust discharge to, and is that acceptable where you are? Fume ducted to the outside of a building still has to be acceptable at the point it leaves.
• What is the bench made of? Acid attacks most work surfaces and most paint. Ask what surface the supplier recommends and plan a drip tray, since the spills happen when flasks are moved.

Handling rules that belong in the standard operating procedure

These are the points a supplier will not write for you and they matter more than any specification on the page:

• Protective equipment is a face shield as well as goggles, an acid-resistant apron and acid gloves, not laboratory coats and safety spectacles. Acid at digestion temperature does not behave like acid in a bottle.
• Never add water to hot acid. Dilution is always acid into water, slowly, and a digest is allowed to cool before anything is added to it.
• Hot flasks are moved in a carrier or rack, never by hand, and never set down on a cold or wet surface, which cracks them. Ask whether a rack and tongs are supplied with the unit.
• The distillation stage uses concentrated alkali added to an acid digest, which is strongly exothermic and can erupt if added too fast. Ask whether the unit adds the alkali through a controlled valve or whether it is poured in, since the former is both safer and more reproducible.
• Have an acid spill kit, an eyewash and a drench shower within reach of the bench, tested, before the unit is commissioned. This is an installation requirement, not an afterthought.

Ask which catalyst the method uses

The classical Kjeldahl digestion was catalysed with mercury or selenium compounds, and many older method sheets still specify them. Mercury catalysts in particular are now avoided, and copper or titanium catalysts are used instead. Ask the supplier which catalyst their method recommends, and ask explicitly whether any reagent supplied or specified contains mercury or selenium. If it does, that brings the handling, disposal and import questions that apply to mercury generally, and your laboratory should settle them before the first run rather than after. A modern copper-catalysed method avoids the issue entirely, so ask for that method sheet.

KDDU-0008 is a different determination, with its own reagent problem

Chemical oxygen demand is a water-analysis test, not a nitrogen determination, so this code sits in the listing because it uses a similar heated digestion block rather than because it does similar chemistry. It matters because of what the standard method uses: a dichromate oxidant, which is a hexavalent chromium compound and a recognised carcinogen, with silver sulfate as a catalyst and, in the classical method, a mercury salt to mask chloride interference.

Before ordering, ask: whether any reagents or pre-dosed vials are supplied and exactly what they contain; whether a mercury-free variant of the method is available, since several exist; how spent digests are to be stored and disposed of, because hexavalent chromium and mercury salts are both restricted waste and this is a recurring cost; and whether sealed vials are used, in which case ask the pressure rating and insist on the correct rack and a shield, since a sealed vial heated to digestion temperature is a small pressure vessel. Confirm that all of this is permitted and disposable where your laboratory is before the apparatus is bought.

The specification to ask for

Once the safety and fume questions are settled, the comparison is straightforward. Ask, against each code: the number of places, which is how many samples run at once and is the figure that sets throughput; the flask or tube size each place takes; the temperature range and, for a dry block (KDDU-0007), the uniformity across the block, since a block that is hotter at one end gives results that depend on where the sample sat; the controller type and whether it can be programmed or timed; the heating time to temperature; and the power rating and supply. For the gas-heated models (KDDU-0002, KDDU-0004) ask the fuel, the consumption and the burner arrangement, and plan cylinder storage, ventilation and a leak-test routine before delivery.

For the distillation stage, ask what the condenser needs in cooling water, whether steam is generated internally or externally, whether the receiver arrangement is included, and whether the quoted unit is a complete determination or only one stage of it. A digestion unit and a distillation unit are two purchases, and KDDU-0006 exists because some laboratories want one.

Also worth confirming

Ask whether KDDU-0003 and KDDU-0005 are the same thing under two names, since one is called a unit and the other an assembly with nothing else to separate them. Ask for the method sheet and the glassware list with the quotation, spares and replacement glassware prices, the installation requirements as a document, the supply voltage, frequency and plug type for your country, and the warranty. Any figure quoted is confirmed in writing on the quotation; ask for its basis.

Related ranges on this site

Solvent extraction and the fat and fibre determinations, which share the fume and flammable-solvent questions, are under Mantles and Soxhlet Apparatus. Solvent recovery is under Rotary Vacuum Evaporator, distilled water for reagents under Water Distillations and Stills, and the meters a water analysis needs under Conductivity and Dissolved Oxygen Meters and TDS Meter, Photocolorimeter and Flame Photometer. Weighing is under Lab Balances and Scales and sterilisation under Autoclaves, Sterilizers and Shakers.

Request a quote

Say how many samples you need to run at once and what you are determining, and ask for the fume arrangement and the method sheet with the quotation. For example a six-place digestion unit (KDDU-0001) with the scrubber type stated and the catalyst named, plus the matching distillation unit, with the installation requirements, the rack and tongs, and the cooling water demand confirmed in writing. Contact Ray Export for specifications, prices and lead times.

Frequently asked questions

Is a fume scrubber needed with the Kjeldahl digestion units?

Yes; it is not an accessory. Hot sulfuric acid digestion produces dense acidic fume that goes into the room and the building's fabric if it is not collected and neutralised. Ask whether a scrubber or exhaust manifold is supplied and what it uses: a water scrubber handles some of the fume, an alkali scrubber handles more. Get the recommendation for the number of places you are buying in writing. Decide whether the unit goes in a fume cupboard or stands on the bench with its own extraction, and check the exhaust is acceptable where it leaves the building.

What protective equipment and handling rules does Kjeldahl work need?

A face shield as well as goggles, an acid-resistant apron and acid gloves, not laboratory coats and safety spectacles. Never add water to hot acid: dilution is always acid into water, slowly, after the digest has cooled. Hot flasks are moved in a carrier or rack, never by hand, and never set down on a cold or wet surface, which cracks them. Alkali added to the acid digest is strongly exothermic and can erupt, so ask whether the unit adds it through a controlled valve. Have a spill kit, eyewash and drench shower tested before commissioning.

Which catalyst should our Kjeldahl method use?

Ask before ordering. Classical Kjeldahl digestion was catalysed with mercury or selenium compounds, and many older method sheets still specify them, but mercury catalysts in particular are now avoided and copper or titanium catalysts are used instead. Ask which catalyst the supplier's method recommends, and ask explicitly whether any reagent supplied or specified contains mercury or selenium. If one does, the handling, disposal and import questions that apply to mercury follow, and should be settled before the first run. A modern copper-catalysed method avoids the issue, so ask for that method sheet.

What is KDDU-0008, and what should we check before buying it?

It is a chemical oxygen demand digestion apparatus - a water-analysis test, not a nitrogen determination - and it sits in this listing because it uses a similar heated digestion block. The standard method uses a dichromate oxidant, a hexavalent chromium compound and recognised carcinogen, with silver sulfate as catalyst and, classically, a mercury salt to mask chloride. Ask whether reagents or pre-dosed vials are supplied and what they contain, whether a mercury-free variant is available, and how spent digests are disposed of. For sealed vials, ask the pressure rating and insist on the correct rack and a shield.

Do we need separate digestion and distillation units?

Usually, yes: a digestion unit and a distillation unit are two purchases, and the combined unit KDDU-0006 exists because some laboratories want one. The electric pair is KDDU-0001 for digestion and KDDU-0003 for distillation, the gas-heated pair KDDU-0002 and KDDU-0004, and KDDU-0007 is a dry block digester. Ask whether a quoted unit is a complete determination or one stage. For distillation, ask the condenser's cooling water demand, whether steam is generated internally or externally, and whether the receiver is included. Ask too whether KDDU-0003 and KDDU-0005 are the same item.

How do we compare the digestion units once safety is settled?

Ask, against each code, the number of places, which sets throughput; the flask or tube size each place takes; the temperature range; the controller type and whether it can be programmed or timed; the heating time to temperature; and the power rating and supply. For the dry block KDDU-0007, ask the temperature uniformity across the block, since a block hotter at one end gives results that depend on where the sample sat. For the gas-heated KDDU-0002 and KDDU-0004, ask the fuel, consumption and burner arrangement, and plan cylinder storage, ventilation and leak testing.

Key takeaways

• The fume scrubber is not an accessory: settle scrubber type, extraction and discharge before comparing codes.
• Kjeldahl work needs acid-grade protection: face shield, goggles, acid apron and gloves, with spill kit, eyewash and drench shower tested first.
• Ask for a copper-catalysed method sheet and whether any reagent supplied or specified contains mercury or selenium.
• KDDU-0008 is a different determination: chemical oxygen demand brings dichromate and possibly mercury waste to plan for.
• Digestion and distillation are two purchases unless you choose the combined KDDU-0006.
• Number of places sets throughput; on the dry block KDDU-0007, also ask the temperature uniformity across the block.

About this page

Ray Export is a manufacturer and exporter of laboratory, scientific and educational equipment based at Plot No. 449, HSIIDC Industrial Area, Saha, Ambala, Haryana 133104, India. Enquiries: [email protected], +91-9817319615.

Written by Palak Mall, Senior Content Writer. Technically reviewed by Arvind Kumar, Lab Equipment Specialist, 12+ years in laboratory and testing instrumentation. Last updated: 18 October 2026.

Specifications, including number of places, temperature range, block uniformity and cooling water demand, are confirmed in writing on the quotation; for certificates, contact us for the latest copies of the relevant certificates. No price is quoted on this page. Listing notes: KDDU-0003 and KDDU-0005 are called a unit and an assembly with nothing else to separate them; and KDDU-0008 is a chemical oxygen demand apparatus rather than a Kjeldahl item.