The lake-water thus concentrated is run into smaller tanks.

It contains carbonate and sesquicarbonate of soda, and common salt.

The addition of lime converts the sesquicarbonate of soda into simple carbonate, and this is separated from the salt by taking advantage of their different points of crystallization.

The salt is partly consumed, and partly used in the extraction of silver from the ore, and the soda is bought by the soap-makers.
Humboldt's remarks on the small consumption of salt in Mexico are curious.

The average amount used with food is only a small fraction of the European average.