I N D U S T R I A L AND ENGINEERING CHEMISTRY
3,000
Vol. 16. No. 3
The Assay of Zinc Ores' Use of Powdered Magnesium for Removing Copper and Lead By E. G. R. Ardagh and G. R. Bongard UNIVBRSITY OF TORONTO, TORONTO, CANADA
HE standard zinc sulfate and potassium ferrocyanide solutions, as well as the conditions for titration, were those described in detail in the preceding article. The reason for substituting metallic magnesium for the metallic aluminium recommended by earlier investigators lies in the fact that, although the presence of aluminium salts does not affect the blank determination, it does very seriously affect the figures obtained when zinc is present, as the following experiments very clearly show: ct of A l u m i n i u m Chloride o n Titration of Zinc by Potassium Ferrocyanide.
diluted to 250 cc. I t was then heated to 70" C. and titrated without filtering. The figures show that the Precipitated copper and lead carry down an appreciable amount of zinc.
Effect on blank. Conditions qame as in earlier determination of blank a s described in the preceding paper K4Fe (CN)c AlCh Required Grams cc. 3 0.20 5 0.20 Bffect of adding al~iminiuinchloride t o 20 cc. standard zinc sulfate KaFe(CN)o Required AIC13 Grams cc. 3 43.05 5 45.30 5 45.95 None 39.45
The end point obtained in this way was somewhat blurred by the small particles of metal and possibly by a little copper having gone into solution. (4) This experiment was a repetition of (3), but the precipitated metals were washed by decantation, then on the filter with &-armhydrochloric acid (5 cc. concentrated hydrochloric acid diluted to 100 cc.).
(2) Eflect of Magnesium Chloride o n Titration oJ Zinc by
The metallic precipitate was boiled with 10 cc. concentrated hydrochloric acid for 5 minutes. Any copper left undissolved was now in a very finely divided state. The solution was diluted to about 75 cc., treated a5 before with magnesium powder, the copper and lead filtered off, and the zinc titrated as above.
T
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Potassium Ferrocyanide. 1 2 grams MgClr.6IlzO added KaFe (,CN)ti Required cc 0 20 0.15 0.15 Effect on titration of iinc. 20 cc. standard zinc sulfate KaFe(CN)ti higCh.6HzO Required Grams c c. 39.50 39.40 10 39.40 30 39.45 39.40 30 Effect on blank.
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L
KdFe(CNj8 Required cc. 38.65
Zinc Separated Grams 0.1960
Zinc Present Per cent 9s 0
On standing 5 minutes longer with vigorous stirring, more zinc entered the solution. KdFe(CNj6 Required CC. 39 20
Zinc Separated Grams 0,1988
KaFe(CN)i Required cc. 36 95
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