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What is Grade 371?

Johnson Test Papers’ Grade 371 filters are acid hardened to allow high retention of fine precipitates in applications such as metal determinations and hydroxide collection.

  • High wet-strength
  • Acid-hardened for resistance to strong acid and alkali solutions
  • Nominal pore size of 2-3 ‎μm
  • Filtration speed of 180 seconds according to DIN 53137
  • Extremely low ash content (0.006% ash maximum)

Along with Grade 371 cellulose filter paper, the Johnson Test Papers range of hardened ashless quantitative papers includes fast Grade 373 and general-purpose Grade 372 filters. All three grades are designed for use in quantitative analysis with strong acid/alkali solutions.

Grade 371 is a very dense and thick filter paper with a slow filtration speed.

This is an extremely fine retention filter for critical gravimetric analysis in chemically harsh conditions and metal determination of very fine precipitates or difficult samples such as metals and hydroxides i.e.

  • barium and lead sulfates and dioxide
  • stannic, zinc and nickel sulfide
  • calcium oxalate
  • calcium fluoride

Whatman Cross Reference = No.50
Speed class Slow
Thickness (mm) 0.25
Pore size (μM) 7-9
Weight (g/m²) 80
Filtration Speed (sec*) 180
Burst Strength (Kg/cm²) >0.3
*According to DIN 53137
Available Sizes
Diameter (mm) Product Code
55 371055
70 371070
90 371090
110 371110
125 371125
150 371150
185 371185
240 341240
300 371300
320 371300