214 
PROFESSOR FORCHHAMMER ON THE COMPOSITION 
26. Sodium. — It is well known that sodium in combination with chlorine forms the 
most important salt in sea-water; next to chlorine, oxygen, and hydrogen, sodium is the 
most abundant element in sea-water. 
27. Potassium is the alkaline element which, next to sodium, occurs most frequently 
in sea-water, and it may easily be shown in the sea-water itself. 
On the Quantitative Analysis of Sea-water. 
It is evident that an analysis which should determine the quantity of every one of the 
substances now enumerated would be a very laborious task, and that the number of 
analyses required to ascertain the composition of sea- water in different parts of the 
ocean would be a work exceeding the power of a single observer. Besides this there 
is another difficulty, which makes a series of such analyses quite impossible ; 100 lbs. 
of sea-water would be the least quantity that could be used, but such a quantity could 
but with difficulty be procured, and could not be kept unaltered by evaporation and 
fermentation. Fortunately such analyses are not required, and of the numerous 
elements discovered in sea-water, only a few occur in such a quantity that their 
quantitative determination can be of any consequence. It is besides a result of my 
analyses of sea-water, that the differences which occur in water from different parts of 
the ocean essentially regard the proportion between all salts and water, the strength 
of sea-water, or, to use another expression, its salinity , and not the proportion of the 
different elements of the salts invicem ; in other words, the difference in the proportion 
between chlorine and water may be very variable, but the proportion between chlorine 
and sulphuric acid, or lime or magnesia will be found almost invariable. The sub- 
stances which, in respect of quantity, play the principal part in the constitution of sea- 
water, are chlorine, sulphuric acid, soda, potash, lime, and magnesia ; those which occur 
in less, but still determinable quantity are silica, phosphoric acid, carbonic acid, and 
oxide of iron. All the numerous other elements occur in so small a proportion, that 
they have no influence whatever on the analytical determination of the salinity of sea- 
water, though, on account of the immense quantity of sea-water, they are by no means 
indifferent, when we consider the chemical changes of the surface of the earth which 
the ocean has occasioned, or is still producing. 
In my complete quantitative analyses I have always determined the quantity of chlo- 
rine, sulphuric acid, magnesia, lime, and potash. The sodium or soda is calculated 
under the supposition that there were no other metalloids or acids than chlorine or 
sulphuric acid, and no other bases or oxides of metals than lime, magnesia, potash, and 
soda ; it was supposed, besides, that the sea-water was neutral. These suppositions are 
not quite correct : of metalloids we find, besides chlorine, bromine, iodine, and fluorine ; 
of acids we find, besides sulphuric acid, also carbonic, boracic, silicic, and phosphoric 
acids ; and of bases we find, besides those that have been enumerated, a great number ; 
but all these substances occur in very small quantities, and may be neglected. I have, 
however, in most cases determined the quantity of insoluble remainder left when sea- 
