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1 2 3 CYANIDE, TOTAL Method 335.3 (Colorimetric, Automated UV) STORET NO. 00720 Scope and Apphcatlon 11 ThIS method IS apphcable to the determmatIOn of cyanIde m dnnkmg and surface waters, domestIc and mdustnal wastes 12 The apphcable range IS 5 to 500 ug/1 Summary of Methods 21 The cyanIde as hydrocyanIc aCId (HCN), IS released from cyanIde complexes by means of UV dIgestIOn and dIstIllatIOn CyanIdes are converted to cyanogen chlorIde by reactIons WIth chloramme-T whIch subsequently reacts WIth pyrIdme and barbItUrIC aCId to gIve a red-colored complex Sample Handhng and PreservatIOn 4 Interferences 31 32 ,,3 3 34 , The sample should be collected m plastIc bottles of 1 hter or larger SIze All bottles must be thoroughly cleansed and thoroughly nnsed to remove soluble matenal from contamers Samples must be preserved WIth 2 m 1 of 10 N sodIUm hydroxIde per hter of sample (pH ~ 12) at the tIme ofcollectIOn Samples should be analyzed as rapIdly as possIble after collectIOn If storage IS reqUIred, the samples should be stored m a refngerator or m an Ice chest filled WIth water and Ice to mamtam temperature at 4°C OXldlzmg agents such as chlonne decompose most of the cyanIdes Test a drop of the sample WIth potassIUm IodIde-starch test paper (KI starch paper), a blue color mdlcates the need for treatment Add ascorbIc aCId, a few crystals at a tIme, untIl a drop ofsample produces no color on the mdlcator paper Then add an addItIOnal 0 6 g of ascorbIc aCId for each lIter ofsample volume 4 1 4 2 ThIOcyanates are a pOSItIve mterference Dunng the UV dIgestIon thIOcyanates are decomposed to cyanIde Sulfides adversely affect the colonmetnc procedure If a drop of the sample on lead acetate test paper mdlcates the presence of sulfide, treat 25 m1 more of the stablhzed sample (pH ~ 12) than that reqUIred for the cyanIde determmatIOn WIth powdered cadmIUm carbonate Yellow cadmIUm sulfide preCIpItates If the sample contams sulfide Repeat thIS operatIOn untIl a drop of the treated sample SolutIon does not darken the lead acetate test paper FIlter the solutIon through a dry filter paper mto a dry beaker, and from the filtrate, measure the sample to be used for analysIs AVOId a large excess of Issued 1978 335 3-1PDF Image | Methods for Chemical Analysis of Water and Wastes
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