Paragraph 7 PROCEDURE

Weigh out 5-10 g of the sample to an accuracy of 1 mg and place in the thimble of the Soxhlet apparatus (5.2).

Wash thoroughly the contents of the thimble with hot water to remove all soluble compounds. Dry in the oven at 90°C (5.4) for at least one hour. Place the thimble in the Soxhlet apparatus (5.2).

• Place a few glass beads in the flask of the apparatus (5.1) and weigh (P₀), then add 50 ml of carbon disulfide (4.1).

• Connect the apparatus, switch on and leave for six hours. Switch off the heat and, after cooling, disconnect the flask. Connect the flask to the rotary evaporator (5.3) and evaporate until the contents of the flask have solidified in a spongy mass.

• Dry the flask in the oven at 90°C (5.4) (generally one hour if necessary) until a constant weight is obtained (P₁).

Certain substances may have been extracted by the carbon disulfide at the same time as the elemental sulfur. The purity of the elemental sulfur is determined as follows:

• homogenize the contents of the flask as thoroughly as possible and remove 2-3 g, weigh to an accuracy of 1 mg (n). Place in the petri dish (5.5). Weigh dish and contents together (P₂). Place on the hot plate (5.6), set at a temperature not exceeding 220°C so as not to cause combustion of the sulfur. Continue sublimation for three to four hours until a constant weight is obtained (P₃).