6 BULLETIN 1226, U. S. DEPARTMENT OF AGRICULTURE. 
Illinois, and Ohio is elsewhere than in these States. Indiana and 
Illinois cokes are made mainly from West Virginia and Kentucky 
coals. Ohio imports coal from Pennsylvania, Kentucky, and West 
Virginia. 
FACTORS GOVERNING VOLATILIZATION OF POTASH IN BLAST 
FURNACES. 
The principal factors which influence the displacement and volatili- 
zation of potash by lime in the cement plant and blast furnace are 
temperature and the proportion of lime to acidic oxides (silica and 
alumina) . The temperatures in the blast furnace are higher than in 
the cement kiln, but in the production of cement clinker the lime- 
stone used is such as to give an approximate ratio of lime to acids 
(Si0 2 + Al 2 3 ) of 2 to 1 while in the blast furnace the ratio of bases 
(CaO + MgO) to acids for smooth running slag is approximately 
1.2 to 1. The sum of the silica and alumina is usually taken as a 
measure of a slag's acidity. On this basis analysis shows most slags 
to be basic compounds having more than 50 per cent of lime and 
magnesia, although this is by no means always the case. 
In the manufacture of ferromanganese and spiegel iron it is neces- 
sary to have a strongly basic slag to prevent loss of manganese in the 
slag. Such furnaces also operate at higher temperatures than those 
making pig iron and greater liberation of potash is therefore to be 
expected at furnaces making these materials. 
The construction of the cement kiln offers an open unobstructed 
passage for the escape of the potash-bearing dust from the kilns and 
owing to the comparatively uniform composition of the materials 
entering and leaving the kilns it is possible to arrive at an approxi- 
mate estimate of the potash in the dust from the analysis of a single 
set of samples of raw mix and ground clinker. 
The conditions which prevail in the blast furnace are entirely 
different. The potash which is volatilized in the hottest part of the 
furnace has to pass up with the gases through the downcoming 
burden toward the upper cooler portions of the furnace where the 
temperature may be as low as 400° or even less. Here it is partially 
condensed to be carried down again to the section of the furnace 
where volatilization temperatures prevail. There is consequently an 
accumulation of potash in the furnace which, under conditions where 
the upper portions become hotter than usual or for other reasons, is 
carried over with the gases from the furnace. The dust collected in 
the flues of the furnace from time to time may therefore vary widely 
in its content of potash. 
The dust collected at points most remote from the furnace contains 
least of the heavier particles of burden carried over mechanically by 
the blast and should therefore contain relatively higher percent- 
ages of potash than that collected in the downcomer and dry-dust 
catcher. 
Analyses of flue dusts collected at various furnaces are tabulated 
in Table 1. 
