Note 2 bis — Chapter X · SODIUM CHLORIDE—BERTHOLLET'S LAWS—HYDROCHLORIC ACID

Chloride of sodium has been found to occur in the atmosphere in the form of a fine dust; in the lower strata it is present in larger quantities than in the upper, so that the rain water falling on mountains contains less NaCl than that falling in valleys. Müntz (1891) found that a litre of rain water collected on the summit of the Pic du Midi (2,877 metres above the sea level) contained 0·34 milligram of chloride of sodium, while a litre of rain collected from the valley contained 2·5–7·6 milligrams.