2 BULLETIN 1226, IT. S. DEPARTMENT OE AGRICULTURE. 
The two manufacturing industries of this country which have the 
largest outputs are the Portland-cement and blast-furnace indus- 
tries. The raw materials used in both these industries contain 
small amounts of potash silicates, and in the process of manufacture 
these materials are ignited with lime at such temperatures that more 
or less of the potash is set free and escapes by volatilization. These 
two industries are already firmly established, and for them the prob- 
lem becomes merely one of the successful recovery of the volatilized 
potash as a by-product. 
RECOVERY OF POTASH IN THE CEMENT INDUSTRY. 
A survey has been made by Ross, Merz, and Wagner 3 of the potash 
that escapes from the cement plants of the country. Representative 
samples of raw mix and of the corresponding ground clinker were col- 
lected from all but four of the cement plants then operating and their 
potash contents determined. With a knowledge of the ratio of raw 
mix consumed to ground clinker produced it was possible to make a 
close estimate of the potash lost from each individual plant. The 
results obtained varied from 0.35 to 5.14 pounds of potash per barrel 
of cement produced, with an average for all plants of almost 2 pounds. 
On the basis of an average production of 90,000,000 barrels, the total 
potash escaping from all the cement plants of this country was estim- 
ated to amount to about 87,000 tons annually. Since these estimates 
were made, installations have been placed in a number of plants for 
the recovery of this potash, and in every case the quantity that was 
found to escape from the kilns closely agreed with the estimates that 
had been made during the course of the survey. It is therefore logi- 
cal to assume the reasonable correctness of the total estimate that 
was made for all the plants of the country. 
During the war active steps were taken at a number of plants to 
recover the potash that escapes from the kilns, and the cement indus- 
try then became an important source of potash in this country. 
METHOD OF INVESTIGATING LOSS OF POTASH IN THE BLAST- 
FURNACE INDUSTRY. 
When the survey of the cement industry was completed a corres- 
Eonding study was undertaken of the potash that escapes from the 
last furnaces of the country. It was originally planned to conduct 
this investigation along lines exactly analogous to those employed 
for the cement industry by obtaining samples of the materials fed 
into the individual furnaces and of the corresponding slags, determin- 
ing the potash in these samples, and then calculating the loss of potash 
per ton of pig iron produced at any given furnace from known ratios 
of ore, flux, coke, and slag to pig iron. It was soon realized, however, 
that this procedure would not be practicable in the case of the blast- 
furnace industry, owing to essential differences of operation in these 
two industries. For the production of cement each individual plant 
is located at or near sources of its raw materials, which are so combined 
that the composition of the finely ground raw mix is fairly constant. 4 
3 Ross, William H., Merz, Albert R., and Wagner, C R. The Recovery of Potash as a Bv-Product in 
the Cement Industry. Bui. 572. U. S. Dept. Agr. , pp. 1-22. 1917. 
* Idem. 
