NOTE ON ESTIMATION OF /[NC IN C01>l>EB 



ORES BY MEANS OF POTASSIUM 



FERROCYANIDE. 



By FRANK E. CONNAH 



Read before the Boyal Society of Queenslavd, 25th September ^ 



1909. 



The accurate estimation of zinc in copper ores by 

 means of Potassium Ferrocyanide as usually recommended 

 is ore which is liable to give trouble, especially if the zinc 

 is only present in small quantity. One is justified in 

 feeling dubious as to the accuracy of results when a blue 

 colour makes its appearance in the solution during the 

 titration, it being almost a certainty that more ferrocyanide 

 is being run in than is required for the zinc ions present ; 

 and while this trouble can usually be aveited by intro- 

 ducing a small crystal of sodium sulphide into the solution, 

 one can feel more confidence in the result obtained when 

 the zinc is previously separated from the main solution 

 and dissolved in o measured quantity of acid. Such a 

 solution is free from oxidising agents and interfering salts, 

 and approaches more nearly to the conditions of the 

 standard. 



The author has been using a process for several years 

 for determining the zinc in copper ores which has invariably 

 given excellent results. The precipitates obtained all 

 allcw of quick filtration, and when one is used to the details 

 of manipulation the process can be quickly carried cut. 

 Briefly, it consists of the separation of manganese by 

 nitric acid and chlorate of potash, iron by ammonia, copper 

 by potassium thiocyanate, and the zinc then is thrown 

 out as a phosphate to be dissolved in a measured quantity 

 of acid, and titrated under standard conditions. 

 ' There are no new reactions in this, but the combi- 

 nation does not appear to have found a place in the 

 journals and text bocks. 



