B. VOLATILIZATION 
1. Add small amount of distilled water to moisten residue in 
crucible. 
2. Add 0.2 ml. of H,SO, (1:1). 
3. Add 10 ml. HF (1:1). 
4. Slowly evaporate to dryness. Do not use oven; avoid loss 
by spattering. 
5. After evaporating to dryness, place in a muffle furnace, 
and ignite to 1000°C for fifteen minutes. 
6. Remove the crucible from the muffle furnace and cool ina 
dessicator; weigh and repeat step 5 until cooled crucible dem- 
onstrates a constant weight. 
7. Record this constant weight. 
5. CALCULATIONS 
A. Subtract values of reagent blanks (see 3., A., B.) from 
weights after evaporation (see 4., A., 18), and after volatiliza- 
tion (see 4., B., 7). 
B. Subtract the corrected weight of the crucible after volatili- 
zation (4., B., 7) from the corresponding corrected weight 
after evaporation and before volatilization (4., A., 18). 
C. The difference X, in milligrams, is the loss on volatiliza- 
tion and represents silica. 
D. Mg. Si0,= X = loss on volatilization. 
6. EVALUATION OF RESULTS 
Compared to lower levels in surrounding soil or material, 
significantly high levels of silica in association with the pres- 
ence of diatoms, indicates past environmental conditions of 
either standing or running water; and in the presence of cer- 
tain phytoliths indicates past grasslands rather than wood- 
lands, and more specifically, in accordance with the phytolith 
classification scheme suggested by D. M. Pearsall, supports 
the identification of the presence of maize in archaeological 
contents. 
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