BUREAU OF SOILS. 299 



in the dust collected at some plants is too low to justify leachino; the 

 material or shippin<>; it as such for direct use as a fertilizer. In order 

 that the potash in such plants may become available, methods must 

 therefore be devised for increasin<T the potash volatilized or decreas- 

 in«i^ the dust that escapes with it ; or the method of recovery must be 

 so modified as to brin<^^ al)out a mechanical separation of the potash 

 and the dust durin<; the process of collection. 



Very unsatisfactory progress has also been made so far in leach- 

 hv^ the potash from the dust, as now collected in commercial plants. 

 A method developed by this bureau has been tested out in the indus- 

 try on a small scale with very satisfactory results, but so far the 

 method has not been applied on an industrial scale. 



A o-reat manv difficulties have also been encountered in collecting 

 the potash-bearing dust as it escapes from the kilns, but judging 

 from results that ha\e recently been obtained with a modified type 

 of installation it would seem that these difficulties are not insur- 

 mountable but simply require time and attention for their solution. 

 In a report issued last year by the Bureau of Mines it was pre- 

 dicted that the cement industry' would shortly become the second 

 most important source of American potash. There is every reason 

 to anticipate that such ma}' be the case, but until the difl^iculties such 

 as have been enumerated are overcome little progress can he ex- 

 pected. Most cement concerns have neither the funds nor facilities 

 for investigating potash recovery, and several companies that have 

 already gone to considerable expense in an attempt to recover potash 

 have now decided to cease operating along this line until the difficul- 

 ties standing in the way of the successful operation of this phase of 

 the industry have been solved by others. 



The situation with regard to the recovery of potash from blast 

 furnaces is very similar to that outlined for the cement industry. A 

 survey of this industry, corresponding to that which was made for 

 cement plants, is now being made by this bureau. The results ob- 

 tained in this work and in lai"ge-scale experiments now being made at 

 two plants in this country go to show that the percentage of potash 

 in the du>t that escapes from some blast furnaces is higher than that 

 contained in the richest cement dust. It is thought, too, that potash 

 can be recovered more economically from blast furnaces than from 

 cement kilns, as other by-products may be recovered in addition to 

 potash, and that the advantages gained from cleaning tlie gases may 

 more tiian cover the cost of collecting the dust. The same problems, 

 however, that remain to be solved in the cement industry are also to 

 be met with in the blast furnace industry, and owing to the relatively 

 small advance that has so far l)een made in the recovery of potash in 

 the latter industry, it is probable that other difficulties now unfore- 

 seen are likel}' to arise. 



It is generally recognized that the potash that escapes from the 

 kilns and furnaces of tliese two industries would, if collected in mar- 

 ketable form, go a long way toward supplying the normal consump- 

 tion in this countiv. Since tlii> is the case, there would seem to be 

 ample justification on the part ui tliis bureau, |)articularly in view of 

 work that has already been acccmiplished in this field, in making a 

 reasonable expenditure for the investigation of such phases of the 

 problem as would properly come witliin the activities of this bureau. 



