BS ISO 17322:2015 pdf download – Fertilizers and soil conditioners — Analytical methods for Sulfur Coated Urea (SCU) 7Determination of the mass fraction of sulfur7.1 Principle Use water and sulfur-saturatedacetone solution to extract water-soluble and acetone-soluble substances,accordingto the sulfur’s behaviour of solubility.Then, extract all the sulfur by carbon disulfide.Calculatethe content of sulfur by the subtraction method. 7.2 Reagents 7.2.1Acetone7.2.2Sulfur, solid. 7.2.3 Carbon disulfide. 7.2.4Sulfur-saturated acetone solution. Add a certain amount of sulfur into acetone, and stir continuously. Some more sulfur should be addedin the acetone as long as the former can be dissolved thoroughly,until sulfur precipitate from acetone. 7.3Apparatus 7.3.1Ordinary laboratory apparatus. 7.3.2 Balance, capable of weighing to the nearest 0,000 1g 7.3.3 Glass crucible filter, No. 4, volume of 30 ml. 7.3.4Drying oven, capable of being controlled at (100 ± 2) ℃.7.4Procedure 7.4.1Determination of the sulfur content Warning —This method of analysis involves the use of carbon disulfide (CS2). Special safetymeasures shall therefore be taken, in particular with regard to the following: the storage of CSz; protective equipment for staff;occupational hygiene; prevention of fire and explosions;-disposal of the reagent. Warning —This method requires a highly skilled staff and a suitable equipped laboratory.The replication experiments shall be done for the determination. Weigh a certain amount of (with 200 mg to 300 mg sulfur contained) as-prepared test sample (crushed)into a 125 ml Erlenmeyer flask with a plug.Add 50 ml of water into the flask precisely before the flasksealed with the plug.Shake the flask vigorously to dissolve the urea content thoroughly.Remove all contents from the triangular flask into a glass crucible filter(7.3.2) which has been dried to a constantweight at (100 ± 2) °C, and then wash the flask five to six times with water. Wash the glass crucible filter and its contents with 10 ml sulfur-saturated acetone solution(7.2.4), thecontent should be dried up by a vacuum pump, repeat this operation four times. Then, dehydrate thesample in the drying oven at (100 ± 2) C for i h; after drying, remove the sample from the dryer andcool it down to room temperature and weigh. Pipette another 10 ml carbon disulfide to wash the test portion, then the content should be dried up bya vacuum pump, repeat this operation 3 to 5 times,until all the sulfur content within the test portionhas been rinsed out. Then, dehydrate the test portion in the drying oven at (100 ± 2) °C for 1 h; after drying,...
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