Clifton E. Meloan Kansas State University Manhattan
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Pvrosulfate FUS~OII of Iron Ore A quantitative analysis experiment '
W h e n dealing with ore samples it is often necessary to fuse the sample to get it into a form thatwill dissolve more readily. However, fusions are seldom, if ever, performed in the laboratory. The reasons for this are somewhat obscure, but they seem to center around the belief that all fusions require expensivecrucibles such as platinum or else they are messy and time consuming. The apparatus described here is inexpensive and can be made by anyone. If properly performed, the student can do a fusion in 30 min without a hood. The experiment, titrimetric determination of iron, was chosen as an example. KHSOI, used as the flux, will fuse iron oxides; and the operation can be carried out in an ordinary flask made of borosilicate glass thus eliminating the platinum requirement. With fusions of this type, considerable SO8is evolved which not only reduces the concentration of flux but over a period of time will add to the general deterioration of the fume hoods. The figure shows a device which drastically reduces the SOz that can escape. Without the condenser the initial temperature a t the mouth of the flask is about 150°C, decreasing quickly to 135% and then to 40-45T after 2-3 minutes. Since Fez(S0Ja has a decomposition temperature of 480°C, there is no danger of losing any iron by this procedure. If the outlet temperature can be kept below 45"C, very few fumes will form. A three to five-tenths gram sample of the iron ore, accurately weighed, is placed in a 125-ml Erylenmeyer flask to which 5 g of powdered KHSO, is added. The flask is swirled to insure adequate mixing, since the melted flux will not wet the surface of lumps and an incomplete fusion will result. Upon gentle heating the KHSOa forms K2S207 (the sample froths and spatters quite badly if heated too fast). This heating will generally require 2-3 minutes. When the frothing is about to stop, the original red-brown solution will turn green and appear to harden. More heat should then be applied. Water will condense in the top of the condenser and some fumes of SOa will combine with the
water to form dense white fumes of H2S0, which will come out of the top of the condenser. These will subside in a few minutes; and although they will never cease, the fuming will reduce to a very low level. At this stage the bottom of the flask should be red hot; and the solution, red-brown. Continue direct heating in the burner flame for 30 minutes, shaking the melt several times. When the melt is cooled (about IOmin), i t will be pure white if the fusion was complete. Grey specks or brown areas indicate incomplete fusion. Reheating is then required. The fused mass can be dissolved in either hot dilute Hi304 or hot dilute HC1.
A, Vigreoux condenser tube; B, An iron ring to h d d the orbedm rquore C in pioce; C , An asbedor square with a 1" hold cut in the c e n t e r i t is not mmdotory but it does keep rome of the he01 away from the condenser; 0, Clamp from the ring stand to the flmrk; E, 125-ml Erlenmeyer fmt which is tilted 10.15' so the1 the melt will cover less area; F, Meeker burner set 7-8 sm below theflask,if closer it will melt the flask.
Volume 39, Number 1 1, November 1 9 6 2
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