FED-STD-791 Lubricants, Liquid Fuels, And Related Products, Testing Method OfThis test method standard is composed of standard test methods for sampling, inspecting and testing lubricants, liquid fuels and related products. It is issued pursuant to the Federal Property and Administration Services Act of 1949, as amended and its application to the purchase of commodities referred to herein is mandatory on all Federal agencies.

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'�NOTE:This draft dated 15 April 2006' by DasH - Page 110 of 460

FED-STD-791D

5.2 Copper powder, ACS. Baker Chemical Company Catalog No. 1728, Copper,

Purified Powder, has been found satisfactory.

5.3 Nitric acid, 5% [2,0,0].

5.4 Acetone, ACS [1,3,0].

5.5 Isooctane, knock test grade [0,3,0].

5.6 Filter paper, Whatman No. 4 and No. 42 or equivalent.

5.7 Firing wire, iron, approximately 26 B&S gage.

5.8 Blue litmus paper.

5.9 Materials required for ASTM D 129.

6. PROCEDURE

6.1 Preparation of copper powder. Place approximately 20 g of copper powder in a

250-mL beaker and add 5% nitric acid until all the powder is covered. Heat the beaker and

contents gently until the surface of the copper powder begins to react. Allow the reaction to

continue for about one minute or until the copper powder is free of oxides. Add sufficient

distilled water to stop the reaction. Decant and discard supernatant liquid. Wash the copper

powder on a No. 4 Whatman or equivalent filter paper with distilled water until the wash water

shows no trace of nitric acid when tested with blue litmus paper. When all the nitric acid has

been removed, wash the copper powder with sufficient acetone to remove all traces of water. If

not ready to proceed with the test, the dried copper powder may be stored under knock test grade

isooctane.

NOTE 1:

Caution. Isooctane is flammable. Do not use isooctane near an open flame.

6.2 Sulfur determinations.

6.2.1 Active sulfur. Place 20 � 1 g of the sample fluid in a 250-mL tall-form lipless

beaker and add approximately 2.0 � 0.1 g of the dried copper powder prepared in 6.1. Place the

beaker and contents on a hot plate and heat the mixture to 149� � 3�C (300�� 5�F) while stirring

at 1750 rpm for at least 1 hour. At the end of the heating and stirring period, cool the mixture to

room temperature and filter through a Whatman No. 4 or equivalent filter paper. Determine the

sulfur content of the filtrate (the reacted fluid) in accordance with ASTM D 129 with the

following exceptions:

Paragraphs 3.2, 3.3: A nickel cup and iron wire may be used

b. Paragraph 5.1: Place 15 mL of sodium carbonate solution in the bomb in place of

the prescribed 5 mL

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