Macherey-Nagel quantitative round filters, type MN 640 w, ash-free, fast-filtering (Ø 55 mm – 320 mm) – 240 mm

The Macherey-Nagel quantitative round filters of the premium MN 640 w grade represent a system solution optimised in terms of materials science and highly efficient in terms of fluid mechanics for precise gravimetric analysis, the quantitative separation of solids and demanding sample preparation in everyday laboratory work. Available in a range of diameters from 55 mm for small-scale analytical applications up to large-area 320 mm filters for high-volume separation processes, this filter series caters for every scale of modern laboratory processes. For quantitative determinations in environmental analysis, metals and building materials chemistry, as well as in pharmaceutical purity testing, the uncompromising purity of the filter medium is the primary criterion for working in a way that is gentle on materials, free from contamination and process-reliable.

Absolutely ash-free for error-free gravimetric analyses

The technological foundation of the MN 640 w grade is based on ultra-pure raw materials such as refined alpha-cellulose and high-quality linters. In a specialised, materials science-based refining process, the paper is washed with acids to achieve an extremely low ash content of less than 0.01 per cent. This absolute ash-free property ensures that, during the subsequent ashing of the filter in a muffle furnace, no transient mineral residues remain that could distort the measurement result on the analytical balance. For B2B testing laboratories, this filter medium thus provides a reliable metrological basis for reproducible and highly precise determinations of weight constancy.

Optimised pore structure for fast kinetics and coarse precipitates

From a fluid mechanics perspective, the smooth round filter is characterised by a deep, wide-pore structure that has been specifically optimised for maximum filtration velocity. With a standardised filtration time of approximately 9 seconds according to the manufacturer’s specification, the MN 640 w grade allows for an extremely rapid liquid throughput. The paper is therefore perfectly suited to the separation of coarse, voluminous and crystalline precipitates (such as iron hydroxide, aluminium hydroxide or coarse metal sulphates). The high porosity minimises transient flow resistance, thereby reducing undesirable blocking effects (filter clogging) in a way that is gentle on the material and ensures process reliability, even with sample flows heavily laden with particles.

High wet tear strength for demanding routine processes

Despite the absence of artificial binders or chemical additives, the homogeneous non-woven fabric possesses remarkable inherent mechanical stability. The optimised fibre interlacing gives the filter high wet tear strength, enabling it to withstand hydrodynamic pressure during funnel filtration or when a light vacuum is applied without any problems. For laboratory managers and quality management personnel in regulated environments, Macherey-Nagel’s MN 640 w filters provide an audit-compliant validation basis for the error-free implementation of recurring quantitative testing processes and certifications in accordance with GLP and GMP guidelines.

Technical details

Material Science & Filter Structure

• Filter type: Quantitative filter paper / Ash-free round filter
• Grade / Quality level: MN 640 w
• Material composition: 100 per cent purest alpha-cellulose and linters
• Finishing: Acid-washed (for maximum purity)
• Ash content: less than 0.01 per cent (ash-free when incinerated)
• Surface structure: Smooth, homogeneously woven
• Filtration properties: Fast filtration (for coarse and crystalline particles)
• Filtration rate: approx. 9 seconds (standardised according to manufacturer’s specifications)

Physical properties & dimensions

• Basis weight: approx. 85 grams per square metre (85 g/m²)
• Filter thickness: approx. 0.20 mm (millimetres)
• Available diameter range: 55 mm to 320 mm
• Diameter variants in the range: 55, 70, 90, 110, 125, 150, 185, 240, 320 mm
• Cut: Geometrically precise, fibre-free circular cut

Resilience & Compliance

• Chemical resistance: Universally inert to mild acids, alkalis and organic solvents
• Wet tear strength: High (structurally stable under fluid load)
• Quality management: Supports standard-compliant gravimetric analyses in accordance with GLP/GMP guidelines

Contents

• 1 x pack of Macherey-Nagel quantitative round filters, grade MN 640 w, ash-free, fast (standard contents: 100 pieces per box) in the diameter selected by the customer (55 mm to 320 mm).

Customised requirements & accessories

To ensure the optimal integration of Macherey-Nagel quantitative filters into your daily analytical routine, we stock a comprehensive range of suitable laboratory peripherals. For conventional vacuum filtration, we offer chemically highly resistant porcelain Büchner funnels, matching borosilicate glass suction flasks and complete multi-filter units. For contamination-free and gentle handling of the ash-free filter discs, we recommend flat-tipped filter tweezers made from high-alloy stainless steel. For subsequent thermal treatment, our range includes high-purity porcelain crucibles, crucible tongs and desiccators for moisture-protected cooling. Please make use of our technical procurement service to tailor the design of your analytical workstations to your specific requirements.