As the requirement for a potable sea water does not arise except in mid-ocean, the proportion of 32 per mille must be taken as the basis of calculation.
This represents as near 20 per mille of chlorine as possible.
From the analysis shown it will be perceived that the chlorides of sodium and magnesium are in great preponderance.
It is to the former of these that the baneful effects of sea water when drunk are to be ascribed, for chloride of sodium or common salt produces thirst probably by its styptic action on the salivary glands, and scurvy by its deleterious action on the blood when taken in excess.
Sodium chloride being the principal noxious element in sea water, and soda in combination with a vegetable or organic acid, such as citric acid, tartaric acid, or malic acid, being innocuous, the conclusion is that the element of evil to be avoided is chlorine.
After describing various experiments, and calling attention to the power of earthy matters in abstracting salts from solutions by which he hoped the process would be perfected, an imperial pint of water from beyond the Eddystone was shown mixed with 960 grains of citrate of silver and 4 grains of the free citric acid.
Each part of the chlorides requires three parts by weight of the silver citrate to throw down the chlorine, thus:
3NaCl + Ag3C6H5O7 = Na3.C6H5O7+3AgCl.
The silver chloride formed a dense insoluble precipitate, and the supernatant fluid was decanted and filtered through a rubber tube and handed round as a beverage.
It contained in each fluid ounce by calculation about: