Letters Sent to Dr. Herman Schlundt, August 29, 1930

August 29th,1930. Dr. Herman Schlundt, Univorsity of Missouri, Columbia, Mo. Dear Dr. Schlundt: In reading Mr. Nahl's thesis, one or two points have occurred to me which might prove helpful in your future investigations of this problem. First, it seams to me, if you are endeavoring to produce a product which will be suitable for commercial uses, that you must get away from the idea of purchasing the highest class of C.P, zine salts available, for after all it would not be practical for commercial operation. thy suggestion would be that you start with some cruder product, such as crude sine chloride or zinc spelter. Nr. Wahl has quite thoroughly established that iron is very detrimental to the final product, and with this should also be included members of the iron and nickle group. I note that when precipitating his solutions with hydrogen sulphide or sodium sulphide, he has tried various methods, that is- where the solution was not saturated with the precipitating reagent, and where precipitation has just been completed, and also with an excess of precipitating reagent. There is an additional state here which might be valuable, and that is to discard the first small amount of precipitate which comes down - in other words, make a. partial precipitation, discarding the first precipitate and utilizing that which comes down only upon addition of further reagents. Such a procedure might have a tendency to remove any detrimental impurities with the first zine sulphide precipitate. In addition to the Clux which Wahl has investigated, I might suggest that you try magnesium chloride - either alone, or in combina- tion with other fluxes. This may not give any better results, but believe it warrants consideration. It seems to me that you should endeavor to maintain a re- ducing atmosphere in the furnace in which this material is roasted. At least the roasting should not be conducted in an oxidizing atmosphere. The addition of sulpher probably provides the necessary reducing atmosphere. As a matter of fact I don't believe that the lids to the crucibles should be luted on, for in the processes of conversion to the phosphorescent form there is considerable gas emitted.