UU-P-236 Paper, Filter, Analytical S/S By Nnn-P-1475This specification covers only the analytical filter papers most commonly used in the laboratories of the Federal Government and does not cover those used in relatively small amounts such as fluted papers.

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UU-P-236a

3.4 Acldity.-The    pH  value  shall  be  not less than  6.0 nor  more than  8.0.

3.5 Ash.-The    ash  of  the  circles of  filter paper  of  all  classes  shall  not   exceed  the amounts specifiedin table I. The ash of other sizes shall be of the same proportion.

TABLE   !.-Maximum     ask  content  of  circles

Ash

Centimeters        Milligrams    Milligrams     Milligrams

5.5        

7.0        

9.0        

11.0        

12.5        

3.8 Workmanship.-The    filter  paper   cirD cles shall  have uniform formation  and  shall be clean and  free  from  imperfections which may affect their  serviceability.

4.  SAMPLING,  INSPECTION,  AND TEST PROCEDURES

4.1 Sampling.-Samples    shall   consist   of fivecartons, each taken from a different shipD ping  container of a  delivery of five or  more containers, or one carton taken  from each of any lesser number of containers in a delivery.

4.2Inspection.-Inspection  of samples shall be  made to  determine  compliance with  this

15.o        

18.5        

1.86            0.186           0.141

4.3 Tests.-Specimens  from each carton of

3.6 Bursting   strength,   time   of   0.ow   of water,  and  retention   of  precipitates.-The bursting   strength,   time  of  flow  of  water, and  retention  of  precipitates  shall  comply with the requirements of table II.

4.3.l  The following tests  shall be made in accordance with  the   methods  described  in Federal SpecificationUU-P-31:

TABLE   11.-Average   bursting  strength,  averD age time  of  flow  of  water,  and  retention  of precipitates

Bursting     Time of

Tests·

Fiber  identification and quantitative determination-------------------D

Alpha-cellulose--------------------- Copper   number                                    _

Acidity, pH------------------------

Method No.

300

201

220

200

strength,      flowof

wet,         water,           Retention of

Class       minimum  maximum        precipitates

I                                               Points        Seconds     Filtrate   clear  from

1--------·      3                20        Ferric  hydroxide.

23 --------·     3.5             40        Lead sulfate.

4              150        Barium sulfate.

4--------·       60              260        Barium sulfate.

5--------·         8                20        Ferric hydroxide.

4.3.2Ask.-The     necessity for a very accuD

rate  determination  of  ash  content,  together

with the  small amount present, requires speD

cial modificationsof the  standard method for

testing  paper.  A large  test  specimen but  as

small an ignition crucible as possible are  reD

quired  for  good accuracy.  These  conditions

are  fulfilled by wetting  the  filter paper  with

distilled   water,   thus    permitting    compact

67--------·,

g        

3.5             40        Lead sulfate.

4                150        Barium sulfate.

4                150        Barium sulfate.

wadding  of  the  paper  for  conservation  of space. The use of a tare  crucible and special precautions  in   the   testing   operations  are

3.7 Type I, class 4.-Type   I, class 4, filter paper  shall  have a  surface  sufficiently hard to  permitpreclpitates   to  be scraped off.

----  --�-

necessary. The test  shall be made as follows:

Use  20-milliliter platinum  crucibles  with covers. A tare cruciblewith a cover is carried

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