0.24 | Alumina (Al2O3) | 16.60 | Silica (SiO2) | 5.19 |\ |
|Lime (CaO) | 55.00 | Ferric Oxide (Fe2O3) | 8.66 | Alumina (Al2O3) | 1.47 | >Feldspar|
|Magnesia (MgO) | 0.36 | Lime (CaO) | 0.25 | Magnesia (MgO) | 0.03 | | 7.34% |
|Carbonic anhydride (CO2) | 43.40 | Magnesia (MgO) | 1.91 | Soda (Na20) | 0.65 |/ |
| | ----- | Soda (Na2O) | 1.00 | | ----- | |
| | 99.92 | Potash (K2O) | 0.45 | | 26.67 | |
| | | Sodium Chloride (NaCl) | 1.86 | | | |
| | | Combined water, organic | | | | |
| | | matter, and loss | 11.36 | | | |
| | | | ------ | | | |
| | | | 100.00 | | | |
+-------------------------+---------+----------------------------+---------+------------------+-------+----------+

Mixing.

Loading the kiln.

[Illustration: FIG. 1]

These materials are mixed in the proportion of about 3:1 by weight so
that the dried mixture contains approximately 75% of calcium
carbonate, the balance being clay. The mixing may be effected in
several ways. The method once exclusively used consists in mixing the
raw materials with a large quantity of water in a wash mill, a machine
having radial horizontal arms driven from a central vertical spindle
and carrying harrows which stir up and intermix any soft material
placed in the pit in which the apparatus revolves. The raw materials
in the correct proportion are fed into this mill together with a large
quantity of water. The thin watery "slip" or slurry flows into large
settling tanks ("backs") where the solids in suspension are deposited;
the water is drawn off, leaving behind an intimate mixture of chalk
and clay in the form of a wet paste. This is dug out, and after being
dried on floors heated by flues is ready for burning. This process is
now almost obsolete. According to pres