[PT032ABZ], Patent Application, Thomas Alva Edison, July 29th, 1889


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[PT032ABZ], Patent Application, Thomas Alva Edison, July 29th, 1889

Editor's Notes

Typed patent application, Case 845: magnetic separation. POSSIBLY SELECTABLE----CLEAR ARTICULATION OF A FUNDAMENTAL PROBLEM OF MAGNETIC SEPARATION, AND ATTEMPT TO DEAL WITH 'MUGWUMP' PROBLEM. Four pages, four claims, one drawing.] "The object of my invention is to provide for the effective separation of magnetic iron ores and more especially to accomplish such separation in the case of what are called 'lean' ores, that is those in which the proportion of iron is very small. ## Ores in which the proportion of iron is less than about thirty per cent have never, before my invention, been economically worked even by my ordinary process of magnetic separation because in the crushed ore therte are many particles which are composed partly of iron and partly of non magnetic material and those are either drawn among the iron particles and diminish the purity of the product, or if by weakening the magnet it is attempted to avoid this, the loss of iron in the tailings is too great. It will be seen that in the lean ores there is a greater proportion of iron particles which are in contact with non-magnetic particles, than in richer ores in which mahy iron particles are in contact with one another, and this is the reason why, in crushing, so many composite particles made up partly of iron and partly of non magnetic material or gangue are formed. ## [Proposes to process tailing of first pass through a different seperator "whose magnet is constructed or situated or energized so as to be of greater strength than that of the first separator. The same machine may of course be used for this second step with its magnet more strongly energized than at first. The magnet for this step of the process is of such strength that it draws over the whole of the composite particles composed both of iron and gangue, and these enter the receptacle c while receptacle d receives only gangue particles. ## I now take the composite product from the receptacle c and crush the same by means of crushing rollers or other suitable apparatus so as to detach or disassociate the iron from the gangue, and, after screening if required, this mingled material is again made to undergo the magnetic separating process in the ordinary manner so as to separate the iron from the gangue. ## This furnishes a very economical process of separation for these poor ores, and one by which a nearly pure oxide ofiron product is obtained and practically no loss of iron takes place in the tailings. [suggests using three different machines to allow continuous processing]



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Thomas A. Edison Papers, School of Arts and Sciences, Rutgers University
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