1677At hlgh acidities, thiocyanate reacts wlth nitrate or other oxidants to produca free cyanlde. For thiocyanate-contalnlng wastewaters, a total cyanide procedure is reported based on use of EDTA at pH 4.0, acetate buffered, to dlsrupt the complexes of cadmlirm, chromium, copper, Iron, nlckel, and rlnc. NRrlte Interference is obvlated by adding sulfamic acid to the sample. Sulfldos are removed from the sample by lnltlal treatment with cadmium carbonate and, If necessary, from dlstliiates wlth aadmlum nitrate.
The spectrographic analysis of volatile acids in a high-purity form is reviewed and a procedure presented that involves evaporation of a 100-g sample under temperature controlled contamination-free conditions and emission spectrography using dc-arc excitation under controlled atmosphere. In the evaporation, graphite (10 mg) is added as a collector, sulfuric acid to convert to less volatile sulfates (with acetic, hydrochloric, and nitric acids), and also mannitol to retain boron (with hydrochloric and hydrofluoric acids). Indium is added as a internal standard. Spectra are examined for 33 elements against a multielement standard in graphite containing indium as an internal standard. For the concurrent analysis of three samples, the elapsed time is 4–10 h and the actual working time 3–5 h. Recovery studies are reported as well as the use of the procedure in the assessment of the leaching of borosilicate glass by concentrated mineral acids.
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