RECOVERY OF POTASH IN THE CEMENT INDUSTRY. 15 



The two sets of analyses shown in this table were made on different 

 samples collected from four months to six months apart. The close 

 agreement in each case affords evidence that at least for these plants 

 the samples collected are representative, and that the potash content 

 of the raw material used in cement manufacture is surprisingly 

 uniform. 



Further evidence in support of this conclusion is available. Thus, 

 R. K. Meade, consulting engineer for the Clinchfield Portland Cement 

 Co., reports * that he found 2.49 pounds of potash volatilized at 

 this plant per barrel of cement, basing his calculations on the 

 results of analyses of samples secured about a year prior to the 

 time that our samples were obtained. This result differs but 0.03 

 pound from that given in Table I. Again, of two samples of raw mix 

 which were collected and forwarded to this laboratory nine months 

 apart by the Tidewater Portland Cement Co., both were found to 

 contain 0.71 per cent potash. 



It may be pointed out also that as a rule those plants which are 

 situated near one another and apparently use material from the 

 same geological formation show much the same potash content in 

 the raw material used. Thus, there may be compared in this con- 

 nection the different plants at Bath, Pa.; Nazareth, Pa.; Fenton, 

 Mich.; Mason City, Iowa; Concrete, Wash.; and Hudson,, N. Y. 



The values listed in Table I for the weights of dry raw mix 

 required per barrel of cement show greater variation than might be 

 expected, and it is possible that some of the values given may depart 

 somewhat from values representing true working conditions. Where 

 no values could be obtained it was assumed that 608 pounds of raw 

 mix would be required per barrel of cement. It is recognized, also, 

 that in individual cases the samples collected may not be representa- 

 tive of normal working conditions, but from the observations made 

 it is thought that in the majority of cases the results given are repre- 

 sentative. 



ESTIMATED PERCENTAGE OF POTASH IN THE FLUE DUST FROM 



DIFFERENT PLANTS. 



The percentage of potash occurring in the flue dust from any 

 plant will vary (1) with the percentage of potash in the raw mate- 

 rial; (2) with the percentage of potash volatilized; and (3) with the 

 amount of dust carried off from the kilns mechanically. 



As already pointed out, the quantity of dust collected daily in 

 the flue stacks and troaters of the plant of the Security Cement 

 and Lime Co. amounts to about 61,000 pounds. If it be assumed 

 that this represents a recovery of 95 per cent of the total dust, 



1 Written communication. 



