Composition of Regular Army Soda-Lime
The exact composition of the army soda-lime has undergone considerable modification from time to time as it has been found desirable to change the raw materials or the method of manufacture. A rough average formula which will serve to bring out the interrelation between the different constituents is as follows:
Composition of Wet Mix
| Per Cent | |
| Hydrated lime | 45 |
| Cement | 14 |
| Kieselguhr | 6 |
| Sodium hydroxide | 1 |
| Water | 33 |
| After Drying | |
| Moisture content | 8 |
| After Spraying | |
| Moisture content | 13 (approx.) |
| Sodium permanganate content | 3 (approx.) |
Within limits, the method of manufacture is more important than the composition or other variables, and has been the subject of a great deal of research work even on apparently minor details. The process finally adopted consists essentially in making a plastic mass of lime, cement, kieselguhr, caustic soda, and water, spreading in slabs on wire-bottomed trays, allowing to set for 2 or 3 days under carefully controlled conditions, drying, grinding, and screening to 8-14 mesh, and finally spraying with a strong solution of sodium permanganate with a specially designed spray nozzle. The spraying process is a recent development, most of the soda-lime having been made by putting the sodium permanganate into the original wet mix. Many difficulties had to be overcome in developing the spraying process, but it eventually gave a better final product, and resulted in a large saving of permanganate which was formerly lost during drying, in fines, etc.