| HS Code | 620799 |
| Product Name | Sodium Hydroxide, 98%, Extra Pure, Pellets 1 KG |
| Chemical Formula | NaOH |
| Molecular Weight | 40.00 g/mol |
| Cas Number | 1310-73-2 |
| Purity | 98% |
| Grade | Extra Pure |
| Form | Pellets |
| Appearance | White odorless pellets |
| Solubility | Soluble in water, 1110 g/L at 20°C |
| Melting Point | 318°C |
| Boiling Point | 1388°C |
| Density | 2.13 g/cm³ at 25°C |
| Ph | 13-14 (1% aqueous solution) |
| Storage | Keep in a tightly closed container in a dry, cool place |
| Hazard | Corrosive; causes severe skin burns and eye damage |
As an accredited Sodium Hydroxide, 98%, Extra Pure, Pellets 1 KG factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Packaging: 1 kg sealed HDPE bottle containing sodium hydroxide 98% extra pure pellets, with safety labeling and moisture-resistant closure. |
| Container Loading (20′ FCL) | 20′ FCL: 1 kg packs of sodium hydroxide pellets palletized and secured; UN1823 corrosive solid, labeled, and loaded per regulations. |
| Shipping | Ship as UN 1823, Class 8 corrosive solid. Pack in airtight, moisture-resistant containers, clearly labeled with hazard warnings. Segregate from acids and metals. Ensure upright, secured palletization to prevent damage. Use PPE during handling. Comply with all applicable land, sea, and air transport regulations for dangerous goods. |
| Storage | Store in a tightly sealed, corrosion-resistant container in a cool, dry, well-ventilated area. Keep away from moisture, water, acids, and incompatible chemicals. Protect from humidity and physical damage. Ensure container is clearly labeled and secured upright. Use appropriate personal protective equipment when handling. |
| Shelf Life | Shelf life is approximately 3 years when stored airtight in a cool, dry place, protected from moisture and carbon dioxide. |
In continuous kraft pulping, a 98% NaOH pellet stock is dissolved in a dedicated caustic dilution skid to maintain white liquor effective alkali because weak black liquor oxidation alone cannot restore hydroxide consumed by acetyl and uronic acid neutralization in softwood chips. The pellet form is metered into a recirculating eductor where dissolution is completed below 60°C to avoid local boiling at the feed throat. White liquor for a Kamyr continuous digester is maintained at 16–20% effective alkali as NaOH on oven-dry softwood, at 30–35% sulfidity, with a liquor-to-wood ratio of 3.0:1 to 4.0:1. The impregnation zone is held at 115–125°C for 25–45 min before the cooking zone reaches 158–170°C. H-factor control is set between 1200 and 1800 for bleachable softwood pulp with a target kappa of 25–35 measured according to ISO 302:2015. If pellet carryover reaches the digester due to bypassing the eductor recirculation loop, localized high-pH spots in the chip column increase shive count and lower pulp viscosity. White liquor analytical checks are performed by TAPPI T 624 cm-15 for active alkali and sulfidity. The terminal product is unbleached softwood kraft pulp for linerboard or sack paper, with subsequent oxygen delignification and chlorine dioxide bleaching stages.
Indicative operating windows for softwood and hardwood campaigns in the same Kamyr digester are tabulated below.
| Parameter | Softwood | Hardwood |
|---|---|---|
| Effective alkali, % NaOH on OD wood | 16–20 | 12–16 |
| Sulfidity, % | 30–35 | 25–30 |
| Cooking temperature, °C | 158–170 | 150–165 |
| H-factor | 1200–1800 | 600–1000 |
| Target kappa by ISO 302:2015 | 25–35 | 14–20 |
Bauxite digestion uses sodium hydroxide as the active lixiviant for gibbsite and boehmite fractions, and the 98% pellet grade is employed as solid make-up to increase spent liquor from 150 g/L to 220 g/L Na₂O before pre-desilication. A low-carbonate caustic source reduces precipitation of sodium carbonate scale in the double-stream heat exchanger and in flash tank inlet piping. In a gibbsitic bauxite campaign, pre-desilication is maintained at 95–105°C for 6–12 h; digestion then proceeds at 145–155°C for 30–60 min, while boehmitic bauxite requires 230–250°C with a residence time of 15–30 min. The pregnant liquor alumina/caustic ratio is held at 0.65–0.75 to avoid premature alumina trihydrate precipitation in the security filtration circuit. Red mud separation in high-rate thickeners is followed by security filtration through trifeed leaf filters; residual suspended solids below 10 mg/L are required before precipitation. The precipitation circuit is seeded with fine gibbsite and cooled from 70°C to 60°C over 36–48 h to grow coarse smelter-grade alumina hydrate. The terminal calcined product is 99.5% Al₂O₃ with a loss on ignition below 1.0%. Published data for this specific trace-metal profile in extra pure caustic on a Bayer refinery is limited, but chloride and calcium carryover from technical caustic are known to accelerate heat exchanger pitting under 250°C digestion conditions, so the extra pure grade is selected where digester tube life is the critical bottleneck.
A 25% w/w lye stock is prepared by adding 1 kg of 98% NaOH pellets to 3 kg demineralized water under mechanical agitation at 50–60°C. The solution is cooled to below 40°C before transfer to the soap kettle to limit ester hydrolysis in the charging line. For a coconut-oil batch with a saponification value of 250 mg KOH/g, the stoichiometric NaOH charge is 178 g NaOH per 1 kg oil; a slight caustic excess of 0.05–0.10% free alkali is carried through to ensure complete triglyceride cleavage. The oil is heated to 80–90°C in a jacketed crutcher with an anchor agitator running at 35–45 rpm. The lye is dosed over 45–60 min; the mixture thickens through the middle soap phase, requiring a temporary increase in agitator torque from 35 A to 50 A on a 15 kW drive. Saponification is continued for 2–3 h until free alkali by ISO 684:1974 falls below 0.1% as NaOH. Sodium chloride at 1.0–1.5% of batch mass is then used to salt out the soap curd, and the lower glycerol/glycerine layer is drawn to a recovery still. The terminal products are sodium coconut-oil soap noodles and 80% crude glycerol. Batch-to-batch variance in free alkali is reduced by filtering the lye through a 100 µm stainless steel screen to remove undissolved pellet fragments before the charging pump.
For feedstocks entering the transesterification unit with an acid number above 4 mg KOH/g, direct alkali-catalyzed reaction is limited by soap formation; the feedstock is first acid-esterified with methanol and sulfuric acid until the acid number falls below 0.5 mg KOH/g. A refined rapeseed oil at 0.35 mg KOH/g is then transesterified with methanol at 25–30% of oil mass and NaOH at 0.3–0.5% of oil mass. The 98% pellets are dissolved in the methanol charge at 30°C to form sodium methoxide in situ; the mixture is fed to a continuous stirred-tank reactor with a Rushton turbine at 120 rpm, held at 60–65°C for 1–2 h. Residual alkaline catalyst is neutralized with 35% hydrochloric acid to a pH of 4.5–5.5, followed by water washing at 50–60°C with 5–10 vol% water. The washed methyl ester is dried at 110°C under 2.5 kPa vacuum and filtered through a 1 µm bag filter. The terminal product is rapeseed methyl ester intended for blending into B7 or B10 automotive diesel, with compliance limits checked against the standard designations in the table below.
| Parameter | EN 14214 | ASTM D6751 |
|---|---|---|
| Acid number, mg KOH/g | 0.50 max | 0.50 max |
| Free glycerin, % m/m | 0.02 max | 0.020 max |
| Total glycerin, % m/m | 0.25 max | 0.240 max |
| Water content | 500 mg/kg max | 0.050 vol% water and sediment max |
| Ester content | 96.5% min | not specified |
A 1.0 N NaOH stock solution is prepared by dissolving 40 g of 98% pellets in 1 L of demineralized water at 20–25°C; the stock is then metered through a positive-displacement diaphragm pump into a 200 mm main before a static mixer of 6 mixing elements. For a low-alkalinity surface water at pH 6.8, caustic dosing of 5–15 mg/L as NaOH raises the finished water pH to 7.5–7.9 and moves the Langelier saturation index toward zero. The treatment chemical must comply with NSF/ANSI/CAN 60 or, in European practice, EN 896:2012 for sodium hydroxide intended for potable water. pH is verified by ISO 10523:2008 or ASTM D1293-18. Local high-pH scaling on the injection quill is managed by maintaining carrier water velocity above 1.5 m/s. Terminal product is finished potable water at the clearwell with pH between 6.5 and 9.5 under the EU Drinking Water Directive. Alkali feed lines are kept free of carbon dioxide ingress because ambient CO₂ absorption forms sodium carbonate crystals in the check valve seat and can cause pump stroke loss.
A chain mercerizer processing 1.5 m wide cotton poplin is charged with 22°Bé NaOH, corresponding to roughly 20–22% w/w NaOH. The 98% pellet grade is dissolved with chilled demineralized water to keep the lye bath at 15–20°C; higher temperatures reduce the degree of cellulose I to cellulose II transformation and produce lower luster. The fabric enters the lye bath under 2,000–4,000 N width-wise tension, dwells for 45–90 s, and then passes through a hot water recovery wash at 70–80°C. Residual alkali is neutralized in a 5 g/L acetic acid bath until fabric pH is 6.5–7.5. The recovered weak lye is evaporated to 30% NaOH and returned to the bath. Terminal products include mercerized cotton shirting, denim warp yarn, and industrial cotton for awning fabric, with tensile strength changes assessed by ASTM D2256-21 and dye uptake measured by reflectance colourimetry. If the lye bath exceeds 25°C, the fabric enters the expander rolls with lower width pickup, causing uneven center-to-selvage tension and non-uniform dye affinity.
Sample digestion vessels for trace metal screening are pH-adjusted with a 0.1 N NaOH solution prepared from 4.0 g of 98% extra pure pellets per 1 L of ASTM D1193-06 Type I water. The solution is standardized against potassium hydrogen phthalate to a factor of 0.999–1.001. The solution is then added to acid-digested sediment or sludge samples to raise the digestate pH from below 1.0 to 6.0–6.5 before syringe filtration through a 0.45 µm PVDF membrane. For ICP-OES, the pH-adjusted digest is diluted gravimetrically to 50 mL and spiked with internal standard. For ion chromatography, a 0.45 µm filter is followed by a guard cartridge to remove residual transition metals. The extra pure grade is selected to avoid trace Fe, Ca, and Zn carryover that would raise blank levels above 10 µg/L in the final prepared sample. Terminal output is prepared sample solution for ICP-OES, ICP-MS, or ion chromatography under ISO 17025:2017 quality control. A carbonate specification of ≤1.0% Na₂CO₃ on the certificate of analysis reduces gas evolution during acid neutralization of open digestion tubes.
In API intermediate synthesis, a 2 M NaOH solution is prepared from 98% extra pure pellets and used to hydrolyze a methyl ester intermediate to the corresponding carboxylic acid sodium salt. The reaction is controlled at 20–30°C in a glass-lined reactor with brine cooling; the pH is held at 12.0–12.5 for 2–3 h. The extra pure grade is selected because technical-grade alkali can introduce iron, lead, and mercury into the hydrolysis stream and approach the permitted daily exposure limits under ICH Q3D. The certificate of analysis for the 1 kg pellet pack is reviewed for carbonate, chloride, and heavy metal results against the current European Pharmacopoeia sodium hydroxide monograph before release. After hydrolysis, the mixture is acidified with 6 M hydrochloric acid to pH 2.0–2.5, extracted with methyl tert-butyl ether, and crystallized from 2-propanol at 0–5°C. The terminal product is a carboxylic acid intermediate with HPLC purity above 99.0% and residual sodium below 100 µg/g by ICP-MS. Process water for dissolving pellets complies with USP <1231> for purified water. Undissolved pellet fines above 0.5 mm are excluded by a 250 µm stainless steel screen on the charging line to avoid local high-pH pockets in the batch. Published data for this specific configuration is limited; the ranges shown are typical for a laboratory-to-pilot scale hydrolysis campaign, not a production-scale isolation train.
Competitive Sodium Hydroxide, 98%, Extra Pure, Pellets 1 KG prices that fit your budget—flexible terms and customized quotes for every order.
For samples, pricing, or more information, please contact us at +8615380400285 or mail to sales2@liwei-chem.com.
We will respond to you as soon as possible.
Tel: +8615380400285
Email: sales2@liwei-chem.com
Flexible payment, competitive price, premium service - Inquire now!
Sodium hydroxide of nominal 98% minimum assay, supplied as white, deliquescent pellets in a 1 kg container, is an extra pure grade of the anhydrous mineral base with CAS registration number 1310-73-2 and molar mass 39.997 g mol⁻¹. The product is characterized by reduced chloride, sulfate, iron, and heavy-metal content relative to technical-grade material, although the term “extra pure” is a supplier designation and not a formal pharmacopoeial or reagent monograph; trace-metal-sensitive work should therefore be supported by the lot-specific certificate of analysis. The pellets have a density of approximately 2.13 g cm⁻³ at 20 °C, a melting point of 318 °C, a boiling point of 1388 °C, and a water solubility of about 111 g per 100 mL at 20 °C. The pellet geometry is selected to reduce dusting during weighing while retaining acceptable dissolution kinetics in aqueous laboratory media. Principal applications include preparation of standard volumetric sodium hydroxide solutions, alkaline hydrolysis, pH adjustment in analytical workflows, and use as a strong-base catalyst for condensation or deprotonation steps requiring a controlled-purity caustic source.
The 98% assay is a total alkali value obtained by acidimetric titration against a standardized acid, with the result expressed as sodium hydroxide. Depending on the method and indicator, the titration may not fully distinguish sodium hydroxide from sodium carbonate; therefore the assay alone does not guarantee absence of carbonate. In an extra pure grade, the specification is intended to control anionic and cationic impurities that can interfere with spectrophotometric, chromatographic, or catalytic downstream steps. The certificate of analysis should state the actual lot data for sodium carbonate, chloride, sulfate, phosphate, iron, and heavy metals, and those values should be compared with the detection limits of the intended method. Published impurity data for this specific supplier configuration is limited, so the certificate of analysis is the controlling document for critical applications. Carbonate is a particularly relevant impurity because sodium hydroxide pellets absorb atmospheric carbon dioxide and moisture during storage, slowly converting surface hydroxide to sodium carbonate and hydrates. For demanding titrimetric work, the solution prepared from the product should be standardized according to ASTM E200-23 against a primary standard such as potassium hydrogen phthalate, using phenolphthalein or potentiometric endpoint detection. The use of freshly boiled water conforming to ISO 3696:1987 grade 2 or better reduces dissolved CO₂ carryover.
Chloride is often determined by turbidimetry or ion chromatography, sulfate by barium sulfate turbidimetry, iron by colorimetric methods after acidification, and heavy metals by sulfide precipitation or ICP-OES. Because “extra pure” is not a harmonized standard, the numerical limits for these analytes are supplier-defined. The 98% minimum assay is therefore more useful as a total-alkali specification than as a direct measure of absolute sodium hydroxide content, because surface carbonation during processing and packaging can shift the effective hydroxide activity without necessarily reducing the total titratable alkalinity below the stated assay.
For the preparation of a 1.0 mol L⁻¹ sodium hydroxide solution, approximately 40.8 g of the 98% product is required per litre, based on the molar mass 39.997 g mol⁻¹ and the nominal assay; a 0.1 mol L⁻¹ solution requires approximately 4.08 g L⁻¹. The pellets are transferred to a tared polypropylene or borosilicate glass beaker and dissolved in a smaller volume of freshly prepared ultrapure water under magnetic stirring. Dissolution is strongly exothermic, with an enthalpy of solution of approximately -44.5 kJ mol⁻¹, sufficient to produce a marked temperature rise if the addition is rapid or the vessel is unstirred. The solution is cooled to 20 °C to 25 °C before quantitative transfer to a volumetric flask and dilution to the final volume with CO₂-free water. Storage of the finished solution in polyethylene or polypropylene bottles is preferred over long-term glass storage because alkaline solutions slowly attack borosilicate glass and may leach trace silicates and boron. For analytical use, standardization is not assumed from the weighed mass; the solution is titrated against dried potassium hydrogen phthalate using phenolphthalein or a calibrated pH electrode in accordance with the general procedure of ASTM E200-23.
Atmospheric carbon dioxide becomes a more significant interference when dilute sodium hydroxide solutions are prepared and stored for acid-base titration because carbonate is introduced as a competing weak base. Under phenolphthalein endpoint conditions near pH 8.2, carbonate is titrated only to bicarbonate, causing the apparent sodium hydroxide concentration to deviate from the true value. This effect is amplified when the solution is exposed repeatedly to air, through loose closures, or when dispensed from containers with large headspace. A carbonate-free solution can be prepared by allowing excess sodium carbonate to precipitate from a concentrated sodium hydroxide solution, because sodium carbonate is only sparingly soluble in strongly alkaline media, and then diluting the clarified liquid with freshly boiled deionized water. Alternatively, a soda-lime guard tube on the storage container slows CO₂ ingress, but no storage system completely eliminates carbonate formation during prolonged use. The impurity burden from the solid pellets is therefore a function not only of the original certificate of analysis but also of storage time, container closure effectiveness, and ambient relative humidity.
The pellet form provides lower dusting and better dispensing control than flake or powder material, while dissolving more slowly than flakes because of the lower specific surface area. This is an operational trade-off: slower dissolution reduces the rate of temperature rise, but it also requires longer mixing times when rapid pH correction is necessary. Technical-grade sodium hydroxide with similar total alkali content can contain higher concentrations of transition metals, chloride, sulfate, and insoluble matter, making it unsuitable for trace analysis, pharmaceutical synthesis, or catalytic systems that are poisoned by iron or heavy metals. Conversely, food-grade or pharmacopoeial sodium hydroxide carries additional compliance requirements under specific monographs; the designation “extra pure” alone does not establish compliance with those regulated end uses. The 1 kg package size limits repeated moisture ingress relative to bulk 25 kg containers, but each opening introduces humid air into the headspace. For a laboratory that consumes caustic slowly, the smaller package can be preferable because the product is exposed to fewer wet-dry cycles before consumption.
Selection of the extra pure grade is frequently driven by the sensitivity of homogeneous or heterogeneous catalysts to chloride and transition-metal impurities. In palladium- or nickel-catalyzed reactions, iron, chloride, and heavy metals can alter induction periods, promote side reactions, or shift product selectivity. A technical-grade sodium hydroxide may be acceptable for bulk neutralization, but its impurity envelope is generally broader and less tightly controlled, which becomes relevant when the base is introduced upstream of a trace-metal-sensitive catalytic step or into an ion chromatograph eluent. For those uses the 98% extra pure material is preferred, but it is not metal-free; if the process requires sub-mg kg⁻¹ transition metal levels, semiconductor or electronic-grade sodium hydroxide, or lot-by-lot screening, should be used.
At the 100 g dissolution scale in a 1 L beaker, the maximum temperature rise observed on a stirred laboratory bench is limited by heat loss to the vessel and ambient air, but the solution can still approach 60 °C to 70 °C if the pellets are added all at once. Adding the solid in portions to a stirred body of water, rather than adding water to the solid, keeps the local hydroxide concentration lower and prevents the formation of a hot, viscous core at the bottom of the vessel. Scale-up to pilot equipment should account for the same exotherm: a jacketed stirred reactor with cooling water and a PTFE or 316L stainless steel impeller is appropriate for dissolving kilogram quantities, while uncontrolled addition in an unjacketed vessel can lead to localized boiling, caustic mist generation, and thermal stress on glass-lined equipment. The dissolution enthalpy of -44.5 kJ mol⁻¹ means that dissolving 1 kg of sodium hydroxide liberates roughly 1.1 MJ of heat, which is sufficient to raise 25 L of water by more than 10 °C under adiabatic conditions; practical systems dissipate much of this heat, but the energy release remains a central design constraint. Mixing equipment should be inspected for compatibility with caustic service; glass, polypropylene, polyethylene, and 316L stainless steel are acceptable for short-term ambient contact, whereas aluminum, zinc, and tin are attacked with release of hydrogen.
Sodium hydroxide of this grade is classified as Skin Corr. 1A under CLP Regulation (EC) No 1272/2008 and carries hazard statement H314, indicating severe skin burns and eye damage. Handling should be conducted with EN 166 chemical splash goggles, nitrile or butyl rubber gloves, and a laboratory coat; a face shield is required when transferring larger quantities or when splashing is possible. The container must be closed immediately after dispensing because deliquescence at high humidity causes surface wetting, caking, and carbon dioxide uptake, with caking becoming pronounced at relative humidity above 60%. If the product has caked from moisture, lot integrity for critical use should be confirmed by assay or water content; drying in a conventional oven can increase carbonate formation and should be avoided. Contact with strong acids, ammonium salts, chlorinated solvents, nitro compounds, and water-reactive metals such as aluminum and zinc must be excluded; mixing with acid without controlled cooling can liberate heat and aerosolized corrosive mist. Spill control should use dry inert absorbent rather than water deluge, because water contact creates a corrosive liquid layer and may spread contamination. Small quantities of sodium hydroxide can be neutralized with dilute citric acid or acetic acid under cooling after compatibility confirmation, but neutralization is itself exothermic and must be performed in a fume hood. Long-term storage in high-density polyethylene or polypropylene containers is preferred over glass, and the product should be stored in a cool, dry, ventilated caustic cabinet away from incompatible chemical classes.
This grade is not intended for direct food, drug, or cosmetic use unless the receiving quality unit verifies compliance with the relevant pharmacopoeial or food-chemical monographs; the “extra pure” label does not substitute for such regulatory determinations. For trace-metal-sensitive syntheses, a lot-specific certificate of analysis and, where critical, an in-house blank digest should establish the acceptable impurity baseline before committing the product to a validated process.
Committed to quality, innovation, and reliable chemical solutions for a sustainable future.
