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Methylene Chloride
- Product Name: Methylene Chloride
- Factroy Site: Binhai New Area, Tianjin, China
- Price Inquiry: sales4@ascent-chem.com
- Manufacturer: Ascent Petrochem Holdings Co., Limited
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- In terms of specification, Methylene Chloride is supplied with 99.9% minimum purity and 50 ppm maximum water content, making it suitable for solvent-based extraction and precision degreasing processes.
| HS Code | 115837 |
| Chemical Name | Methylene Chloride |
| Chemical Formula | CH2Cl2 |
| Cas Number | 75-09-2 |
| Molecular Weight | 84.93 g/mol |
| Appearance | Colorless liquid |
| Odor | Sweet, chloroform-like odor |
| Density | 1.326 g/cm³ at 20°C |
| Melting Point | -96.7°C |
| Boiling Point | 39.6°C |
| Vapor Pressure | 47.4 kPa at 20°C |
| Solubility In Water | 2 g/100 mL at 20°C |
| Autoignition Temperature | 556°C |
| Refractive Index | 1.4244 at 20°C |
As an accredited Methylene Chloride factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Methylene chloride is packaged in 55-gallon steel drums with secure lids, clearly labeled for safe handling and transport. |
| Container Loading (20′ FCL) | Container loading of Methylene Chloride in 20' FCL requires UN-approved packaging, vertical securing, and ventilation to prevent vapor accumulation. |
| Shipping | Methylene chloride (dichloromethane) is shipped as UN 1593, Hazard Class 6.1, Packing Group III. Transport in tightly sealed, properly labeled containers, inside ventilated, leak-proof packaging. Avoid contact with incompatible materials, keep away from strong oxidizers, and handle with appropriate personal protective equipment to prevent toxic vapor exposure. |
| Storage | Store methylene chloride in tightly sealed, labeled containers in a cool, dry, well-ventilated area, away from direct sunlight, heat, and moisture. Keep isolated from strong oxidizers, acids, bases, and reactive metals. Use corrosion-resistant secondary containment, ground containers to prevent static, and ensure access to eyewash/safety equipment. Monitor for leaks and maintain low temperature to limit vapor buildup. |
| Shelf Life | Methylene chloride has a shelf life of approximately 2–3 years when stored tightly sealed in a cool, dry, dark place. |
Interfacial polycondensation of bisphenol A and phosgene for polycarbonate resin is carried out in a two-phase reactor in which methylene chloride functions as the continuous organic phase. The solvent is charged at a solvent-to-bisphenol A mass ratio of 4.0:1 to 6.0:1 during initial reactor feed, and the organic phase is maintained at 10–20 wt% polycarbonate during chain extension; this range balances phase separation speed, sodium chloride removal, and molecular weight build. Resin intended for food-contact articles is evaluated under FDA 21 CFR 177.1580 and EU Regulation 10/2011, with residual methylene chloride reduced through washing and devolatilising twin-screw extrusion. The production sequence includes phosgenation at pH 10–12, phase separation, dilute hydrochloric acid and deionised water washing, steam precipitation, and final extrusion at 280–310°C with vacuum ports below 100 mbar. Terminal finished product types include optical-grade polycarbonate sheet, automotive glazing blanks, medical device housings, and optical disc substrate resin.
On production-scale lines using glass-lined reactors with pitched-blade turbine impellers and baffles, phase separation time in the decanter increases when the organic phase exceeds 20 wt% polycarbonate, because continuous-phase viscosity rises above 1,500 mPa·s at 25°C. To avoid salt carryover into the devolatilising twin-screw extruder, the washed organic phase is controlled to a water content below 0.5 wt% before steam precipitation; extruder barrel temperatures are held at 280–310°C with vacuum devolatilisation to strip residual methylene chloride below 100 ppm in the pellet feed. Batch-to-batch variance in this application is most frequently traced to insufficient methylene chloride removal from the aqueous phase after washing, which raises residual chloride in the finished resin and reduces colour stability during injection moulding.
Can Methylene Chloride Maintain ICH Q3C Class 2 Residual Limits in Alkaloid Extraction?
Solvent extraction of plant-derived and fermentation-derived intermediates with methylene chloride is typically configured as a multi-stage countercurrent liquid-liquid operation, in which the solvent-to-feed mass ratio is set between 3.0:1 and 10.0:1 depending on target partition coefficient and emulsion behaviour in the decanter centrifuge. The process begins with pH-adjusted aqueous broth or extract, followed by countercurrent contact in mixer-settler trains or centrifugal extractors, phase separation, vacuum distillation at 30–40°C to recover methylene chloride, and crystallisation or precipitation of the target API intermediate. Residual solvent is driven below the ICH Q3C(R8) Class 2 concentration limit of 600 ppm and verified according to USP <467>; when the downstream step is a spray-dried or lyophilised finished drug product, drying parameters must account for the 6.0 mg/day permitted daily exposure. Terminal finished product types include corticosteroid intermediates, antibiotic precursors, alkaloid APIs, and vitamin E-derived tocopherol concentrates.
Production-scale extraction lines report that phase inversion in the decanter centrifuge becomes likely when the aqueous phase ionic strength drops below 2–5 wt% dissolved solids, and methylene chloride carryover into the crystallisation vessel rises when the vacuum distillation condenser temperature exceeds 10°C. The main operational boundary is associated with heat-sensitive APIs: solvent recovery must be conducted under vacuum to keep process-stream temperature below 40°C, otherwise degradation impurities increase beyond the specification limit for the finished active ingredient. Published data for specific ternary extraction configurations is limited because pharmaceutical process parameters are proprietary, but the solvent-to-feed range cited above is consistent with reported industrial countercurrent equipment performance.
Vapor Degreasing Bath Chemistry, Stabilizer Depletion Rates, and Ultrasonic Energy Limits
Precision cleaning of metallic components with methylene chloride is performed in open-top vapor degreasers or vacuum degreasers in which the solvent is used neat, with stabilizer packages added at 0.1–1.0 wt% to suppress thermal decomposition to hydrogen chloride. Operating temperature is maintained at the boiling point of 39.6°C, while ultrasonic transducer density is commonly set at 25–50 W/L in the immersion sump to avoid cavitation-induced stabilizer depletion on aluminium and zinc workpieces. The process sequence includes immersion in the boil sump, ultrasonic agitation, vapor rinse, and freeboard chilling; part baskets are sized so that mass throughput does not disrupt vapor equilibrium. Compliance obligations include OSHA 29 CFR 1910.1052, with an 8-hour time-weighted-average permissible exposure limit of 25 ppm and a 15-minute short-term exposure limit of 125 ppm, plus the degreasing line NESHAP requirements in 40 CFR Part 63 Subpart T and operation according to ASTM D3698. Terminal finished product types include aircraft hydraulic actuator components, precision bearing races, medical instrument blanks, and stainless-steel valve bodies.
Production experience identifies water ingress as the primary root cause of methylene chloride vapor degreaser failure; water content above 0.1 wt% accelerates hydrolysis to hydrogen chloride, causing pitting on ferrous workpieces and requiring immediate solvent distillation or replacement. The operational boundary for light-metal loads is defined by stabilizer consumption: when dissolved aluminium chloride begins to form at the solvent-metal interface, stabilizer depletion is visually indicated by a drop in acid acceptance below 0.01 wt% of the solvent charge, and the bath must be re-stabilised before further processing. The same limitation applies to zinc die-cast parts, which are processed only in methylene chloride stabilised with non-amine additive packages to prevent galvanic corrosion. Published data for this configuration is documented in equipment vendor technical bulletins for vapor degreasing systems and solvent-stabilizer acidity tests.
In continuous flexible polyurethane slabstock foam production, methylene chloride is metered into the polyol stream as an auxiliary physical blowing agent at 2–10 parts per hundred polyol (php), with the exact addition rate set to offset foam exotherm and control core discoloration when water-isocyanate chemical blowing alone cannot achieve target density. The production process uses low-pressure or high-pressure continuous mixheads that discharge into a traversing trough; the liquid reaction mixture then passes through a fall plate and side-paper conveyor into a round block or rectangular block tunnel, where the methylene chloride is volatilised by the exothermic reaction at 120–160°C and stripped with forced-air ventilation. Methylene chloride-bearing slabstock lines in the United States are subject to 40 CFR Part 63 Subpart III NESHAP for flexible polyurethane foam production, and workplace exposure is limited under OSHA 29 CFR 1910.1052 at 25 ppm 8-hour TWA. Terminal finished products sliced from methylene chloride-blown slabstock include conventional foam mattresses, furniture cushioning, automotive seating inserts, and carpet underlay; where the CertiPUR-US® certification program applies, methylene chloride-blown foam is excluded and alternative physical blowing agents or all-water formulations are specified.
The main process conflict is foam exotherm control: below 0.8 php the auxiliary cooling effect is negligible, while above 12 php the combined heat of vaporisation reduces block core temperature too rapidly, yielding closed-cell defects and split blocks on high-throughput Maxfoam lines. Production operators also monitor the gel-blow balance through pour rate and conveyor angle because methylene chloride reduces viscosity and can cause side-cell collapse if the fall plate temperature falls below 35°C. On slabs longer than 30 m, forced-air extraction must remove methylene chloride from the tunnel at a rate sufficient to keep the operator zone below the 125 ppm short-term exposure limit, but excessive airflow can create surface skin closed-cells in low-density grades below 14 kg/m³.
When Methylene Chloride Is Selected as the Primary Diluent in Chloroprene Contact Adhesives
Chloroprene contact adhesives are compounded by masticating polychloroprene rubber on a two-roll mill at 40–60°C, then dissolving the polymer in a solvent blend containing methylene chloride at 10–40 wt% of the total adhesive formulation, together with tackifying resins, magnesium oxide, zinc oxide, and antioxidant. The methylene chloride addition ratio is adjusted within that range to achieve a Brookfield viscosity of 2,000–8,000 mPa·s at 25°C, which is required for roll-coater or doctor-blade application without stringing. The downstream production process includes closed high-shear mixing under nitrogen to prevent methylene chloride vapour accumulation, filtration through 50–100 µm bag filters, continuous coating onto leather, polyurethane foam, or high-pressure laminate, two-stage drying at 35–45°C, and lamination under nip pressure. Compliance for industrial adhesive users in the European Union is governed by REACH Annex XVII entry 59, which restricts supply to general consumers but permits professional and industrial use when exposure controls are in place; in the United States, OSHA 29 CFR 1910.1052 applies to methylene chloride-exposed workers. Terminal finished product types include automotive interior door panel laminates, office furniture edge banding, footwear leather-to-rubber bonds, and construction sandwich panels.
A process-specific incompatibility arises when amine-curing agents or alkaline fillers are introduced into methylene chloride-rich formulations, because free amine accelerates solvent decomposition and generates corrosive hydrogen chloride, reducing shelf life and increasing adhesive pH beyond the 10.0 stability threshold. Production records from sealed adhesive mixers show that batch-to-batch viscosity drift above ±15% is most often traced to moisture ingress through the raw-rubber feed, which competes with methylene chloride for magnesia and shifts the gel network before coating. Open mixing vessels are therefore excluded from industrial operations unless a closed nitrogen blanket and condenser are installed on the mixer, because methylene chloride vapour density is greater than air and accumulates at floor level.
Industrial Coating-Removal Formulations Require a 50–90 wt% Methylene Chloride Active Phase
Methylene chloride-based industrial coating removers are formulated with 50–90 wt% methylene chloride as the active solvent phase, combined with paraffin wax evaporation retardants, cellulose ether thickeners at 0.5–3.0 wt%, and co-solvents such as methanol or toluene at 5–15 wt% to regulate evaporation rate and brushability. The production process for the remover itself involves sealed low-shear blending at 20–30°C, wax dissolution pre-heated to 50–60°C, and filling into lined steel or HDPE containers; at the downstream applicator, the product is applied by brush, flow-coater, or spray to aircraft, marine, or metal furniture surfaces and allowed to dwell for 15–60 minutes before mechanical scraping or water rinsing. Compliance obligations for industrial coating removal are defined by OSHA 29 CFR 1910.1052 with 25 ppm 8-hour TWA and 125 ppm 15-minute STEL, and by EPA TSCA Section 6(a) restrictions codified at 40 CFR Part 751, which prohibit consumer sales but permit industrial workplace use when the chemical protection program requirements are met. Terminal finished product types are the prepared substrate: aircraft fuselage skins prior to non-destructive inspection, automotive body panels before repainting, marine hull plates before re-coating, and architectural metal extrusions before powder coating.
The operational boundary is the temperature-viscosity trade-off: below 10°C the high-viscosity film becomes too slow to penetrate epoxy primers, while above 35°C the paraffin wax layer volatilises too rapidly and the methylene chloride flash evaporation reduces effective contact time to less than 8 minutes on steel substrates. Production applicators further report that sprayed methylene chloride paint removers require pressure-pot settings below 30 psi and gun distances above 45 cm to prevent atomised solvent from drying before film coalescence; airless pressure above 50 psi produces dry overspray and incomplete primer lifting on riveted aluminium surfaces. Published data for this configuration is available from coating-stripping equipment manufacturers but varies by substrate thickness and coating age.
Food-grade extraction with methylene chloride under 21 CFR 173.255 is confined to caffeine removal from green coffee beans and tea leaves, as well as the production of certain hop extracts and spice oleoresins, with residue limits specified in the regulation. The extraction process begins with steamed and water-swollen green coffee beans or milled spice feedstock, followed by countercurrent extraction in sealed extraction batteries at a solvent-to-feed mass ratio of 2.0:1 to 8.0:1, separation of miscella, and solvent recovery by vacuum stripping at 40–45°C; for decaffeination, the methylene chloride is recycled and the caffeine-bearing extract is routed to caffeine recovery. The finished food ingredient must be dried to reduce residual methylene chloride below the regulatory limit, with decaffeinated roasted coffee and decaffeinated soluble coffee extract controlled to a maximum of 10 ppm under 21 CFR 173.255; analytical verification is performed by headspace gas chromatography with flame-ionisation detection. Terminal finished product types include decaffeinated roasted coffee, decaffeinated instant coffee, hop extract for brewing, and spice oleoresins for processed flavour systems.
Published data for this configuration is limited with respect to batch-to-batch residual solvent variability because decaffeination line parameters are proprietary; however, extraction plants report that green bean charge moisture above 45 wt% causes swollen seed tissue and bed compaction, reducing solvent percolation and requiring a shorter extraction cycle with more frequent desolventising. The main operational boundary in food-grade extraction is the separation of methylene chloride from heat-sensitive oils: vacuum stripping must remain below 45°C to avoid thermal degradation of coffee oil and spice oleoresin, while residence time in the stripper must exceed 20 minutes for feeds with more than 3 wt% residual moisture. Solvent loss in the waste-water stream is controlled by carbon adsorption or steam stripping before discharge, because methylene chloride is denser than water and can accumulate below the aqueous phase in unvented collection tanks.
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- Methylene Chloride is manufactured under an ISO 9001 quality system and complies with relevant regulatory requirements.
- COA, SDS/MSDS, and related certificates are available upon request. For certificate requests or inquiries, contact: sales4@ascent-chem.com.
Methylene chloride, CAS 75-09-2, is a chlorinated aliphatic solvent produced by chlorination of methane or by reaction of methanol with hydrogen chloride. The molecule CH2Cl2 has a molar mass of 84.93 g/mol, a normal boiling point of 39.8 °C, a density of 1.326 g/cm3 at 20 °C, and a vapour pressure of 47.4 kPa at 20 °C. Commercial supply is organised by application-based grades rather than a single universal model: technical grade, vapour degreasing grade, polyurethane grade, and pharmaceutical grade differ in stabilizer composition, water content, acidity as hydrogen chloride, and nonvolatile residue. A certificate of analysis normally reports gas chromatographic purity, Karl Fischer water, colour against the platinum-cobalt scale under ASTM D2109, and acidity under the relevant methods of ASTM D4701. The solvent is described as nonflammable under ordinary closed-cup test conditions, but the vapour can form flammable mixtures when oxidant concentration and ignition energy depart from ambient norms. Handling therefore prioritises vapour inhalation control and thermal decomposition management rather than classic flash-fire prevention.
What Separates Technical, Vapour Degreasing, and Polyurethane-Grade Methylene Chloride?
Commercial specifications for methylene chloride are not defined by a universal model number but by end-use stabilizer packages and impurity ceilings. Vapour degreasing grades contain acid-accepting stabilizers that neutralise trace hydrogen chloride formed by hydrolysis or oxidative decomposition; technical grades may carry lower stabilizer additions. Polyurethane-grade material is controlled for pH, water, and iron to avoid interference with isocyanate reactions, while pharmaceutical-grade material is assayed against residual solvent criteria. Supplier certificates frequently list purity of 99.9% or higher for vapour degreasing material, water content below 100 mg/kg in dried grades, acidity as HCl below 5 mg/kg, and evaporation residue below 10 mg/kg. These values are not universal; each certificate must be read against ASTM D4701 and the downstream operation. Colour of halogenated solvents is determined by ASTM D2109 using platinum-cobalt reference solutions. Water is measured by Karl Fischer titration, often following ASTM D1364. Iron and chloride content are sometimes specified for tanker or drum transfer because residual moisture and acid species can consume stabilizer during storage.
In polycarbonate resin washing, methylene chloride is selected because the interfacial polymerization route can use the solvent for phosgene or oligomer dissolution before phase separation. The low boiling point reduces thermal energy required for solvent recovery, but the same volatility requires closed-loop condensation and demister control. Solution viscosity depends on resin molecular weight and solids loading; rotational rheometry under ISO 3219 is used to characterise shear-thinning behaviour before filtration. Because the solvent has higher density than water, phase separation places the dense organic layer at the bottom of wash vessels, and decanting lines must be designed for water removal above the solvent interface. Published data for this specific configuration is limited because resin producers use proprietary solids loadings and wash-train designs; however, the density difference is the controlling variable in continuous separation.
Vapour Degreaser Acid Acceptance, Stabilizer Depletion, and Solvent Drag-Out
Vapour degreasing with methylene chloride is operated in stainless steel or mild steel sumps fitted with water separation and continuous filtration. The boiling sump is held at the vapour temperature of the solvent, approximately 39.8 °C, which removes oils and waxes without exposing aluminium components to the thermal stress encountered in higher-boiling chlorinated solvents. However, the low boiling point also produces a high vapour generation rate; freeboard refrigeration is typically set below 10 °C to reduce solvent emissions. Equipment with freeboard ratio lower than 1.0 tends to increase drag-out and diffusion loss, especially when parts enter or leave the vapour zone at high speed. Ultrasonic transducers in the liquid sump, usually operated between 25 kHz and 40 kHz, improve particulate removal from blind holes and recessed surfaces.
Acid acceptance is measured by titration of solvent from the sump after contact with water and metal coupons; a decline in acceptance capacity indicates stabilizer depletion. In production operations, methylene chloride is stabilised to maintain acid acceptance above the threshold specified by the solvent supplier. When aluminium fines, strong alkalis, or excessive water are introduced, the solvent can generate hydrogen chloride and, under severe conditions, trace decomposition products. The stabilizer package is consumed faster in the presence of light, water, and copper or zinc alloys. Sump solvent should be checked for pH and acid acceptance after solvent additions, and the water separator drained before acid layers induce corrosion. This is a critical process window because solvent condition near the acid-acceptance limit produces rapid pit corrosion on mild steel vapour lines and pump internals.
Pharmaceutical extraction operations use methylene chloride as a low-temperature extraction solvent for heat-sensitive intermediates and for chromatographic isolation of nonpolar actives. Residual solvent limits are set by ICH Q3C; methylene chloride is a Class 2 residual solvent with a permitted daily exposure of 6.0 mg/day and a concentration limit of 600 ppm in the final medicinal product unless otherwise justified. Recovery trains normally use closed-loop condensation and decanting because the solvent is only slightly soluble in water and separates rapidly from aqueous process streams. Carbon adsorption or nitrogen stripping is applied to vent lines where condensation alone cannot meet emission limits. The low boiling point permits distillation at mild thermal conditions, which reduces degradation of thermally labile actives; however, condensation equipment must be designed for high vapour volume per unit mass of recovered solvent.
When Low Boiling Point Becomes an Exposure-Control Variable in Coating Removal
Paint stripping formulations based on methylene chloride combine the solvent with paraffin wax or cellulosic thickeners to control evaporation and reduce inhalation exposure during dwell times. The active solvent penetrates cross-linked coatings by swelling and rupturing the film; the evaporated solvent condenses on cooled surfaces and can displace oxygen in low-lying areas. Because the vapour pressure at 20 °C is 47.4 kPa, an open tray generates concentrations above the 29 CFR 1910.1052 action level of 12.5 ppm unless engineering controls are used. The OSHA permissible exposure limit is 25 ppm as an 8-hour TWA, with a short-term exposure limit of 125 ppm. Local exhaust capture velocity and air monitoring are therefore part of any production-scale removal procedure.
Compared with N-methyl-2-pyrrolidone, methylene chloride evaporates faster and provides shorter dwell time for film separation on many epoxy and alkyd systems; however, NMP has a higher flash point of 91 °C and much lower vapour pressure of 0.04 kPa at 20 °C, making it less volatile but slower to evaporate. Compared with trichloroethylene, methylene chloride has a lower boiling point and higher vapour pressure, which can raise exposure intensity but also reduces required sump heat input. In closed equipment, the exposure boundary rather than flammability limits open-tray use.
Regulatory restrictions shape the application of methylene chloride in paint stripping. Within the European Union, REACH Annex XVII entry 59 prohibits placing paint strippers containing methylene chloride at or above 0.1% on the market for supply to the general public. Professional use is subject to risk-management measures and often requires closed application systems or ventilated enclosures. These restrictions do not apply to every industrial use; solvent recycling and waste disposal remain governed by hazardous waste classification under national and regional controls. In the United States, methylene chloride remains listed as an exempt volatile organic compound under 40 CFR 51.100(s) for photochemical reactivity purposes, although workplace exposure and hazardous air pollutant requirements still apply. It is not controlled as an ozone-depleting substance under the Montreal Protocol.
Comparative Physical Property Matrix for Halogenated and Non-Halogenated Alternatives
Selection between methylene chloride and replacement solvents depends on boiling point, density, water solubility, vapour pressure, and regulatory status. The following matrix summarises published physical data for pure liquids. Values are typical and should be confirmed against the supplier certificate before equipment design.
| Property | Methylene chloride | Trichloroethylene | Perchloroethylene | 1,2-Dichloroethane | N-Methyl-2-pyrrolidone |
|---|---|---|---|---|---|
| CAS | 75-09-2 | 79-01-6 | 127-18-4 | 107-06-2 | 872-50-4 |
| Formula | CH2Cl2 | C2HCl3 | C2Cl4 | C2H4Cl2 | C5H9NO |
| Molar mass | 84.93 g/mol | 131.39 g/mol | 165.83 g/mol | 98.96 g/mol | 99.13 g/mol |
| Normal boiling point | 39.8 °C | 87.2 °C | 121.2 °C | 83.5 °C | 202 °C |
| Density at 20 °C | 1.326 g/cm3 | 1.464 g/cm3 | 1.623 g/cm3 | 1.253 g/cm3 | 1.028 g/cm3 |
| Vapour pressure at 20 °C | 47.4 kPa | 7.8 kPa | 1.9 kPa | 8.3 kPa | 0.04 kPa |
| Water solubility at 20 °C | 13 g/L | 1.28 g/L | 0.15 g/L | 8.7 g/L | Miscible |
| Flash point | None reported under standard closed-cup testing | None reported under standard closed-cup testing | None reported under standard closed-cup testing | 13 °C | 91 °C |
Compliance and Occupational Exposure Checklist
Compliance for methylene chloride handling is organised by exposure route and end-use restriction. The following matrix lists principal published benchmarks that appear on safety data sheets and regulatory submissions.
| Standard or code | Measure or limit |
|---|---|
| 29 CFR 1910.1052 | OSHA TWA PEL 25 ppm; STEL 125 ppm; action level 12.5 ppm |
| ACGIH TLV | TWA 50 ppm; current adoption should be verified against the latest published documentation |
| ICH Q3C | Class 2 residual solvent; PDE 6.0 mg/day; concentration limit 600 ppm |
| REACH Annex XVII entry 59 | Paint stripper restriction at ≥ 0.1% for supply to the general public |
| 40 CFR 51.100(s) | US EPA VOC exemption based on negligible photochemical reactivity |
| ASTM D4701 | Technical grade methylene chloride specification |
| ASTM D2109 | Colour test for halogenated organic solvents |
Storage of methylene chloride in carbon steel drums is acceptable when water is excluded, but aluminium, magnesium, sodium, potassium, and zinc in finely divided form should be isolated from the liquid and vapour. Drum pumps should be stainless steel or PTFE-lined because the solvent swells many elastomers and strips protective oils. Bulk storage tanks should be earthed and vented through activated carbon or condensation recovery; nitrogen blanketing reduces moisture uptake. If water content rises above 100 mg/kg, stabilizer drain increases and the acid-acceptance reserve should be measured before the solvent is returned to process duty.