a) Silicates are stronger alkalis since their (Si O 2 / Na 2 O) ratio is low. For sodium silicates, this ratio can be changed by optionally adding sodium hydroxide. The pH value of silicate solutions is relatively high. For example, 2O metasilicate pH for 5H is 30 grams / liter solution 12.8. This alkalinity has the same advantages over organic soils as sodium carbonate.