206 
PROFESSOR FORCHHAMMER ON THE COMPOSITION 
its presence may be ascertained with great facility. To prove directly its existence in 
sea-water, I evaporated 100 lbs. of it taken in the Sound near Copenhagen, and when 
it was so much condensed that the salt began to crystallize, I precipitated the whole 
by an excess of ammonia, washed the precipitate, and dissolved in muriatic acid. It 
was now again precipitated by ammonia, and the precipitate boiled with a solution of 
muriate of ammonia. The washed precipitate weighed now 3T04 English grains, and 
was divided into two parts, of which one was heated in a small platinum crucible with 
sulphuric acid. The vapours etched glass. The other part was distilled in a bent glass 
tube with sulphuric acid, and the vapour condensed in a solution of ammonia. The 
vapours etched the glass tube, and when the ammoniacal liquor was evaporated and the 
salt dissolved, silica remained. With much greater facility the fluorine was shown in 
the stony matter deposited at the bottom of the boilers of the Transatlantic steamers, of 
which I owe samples to the late Dr. G. Wilson of Edinburgh, who likewise discovered 
fluorine in sea-water. 
7. Sulphur . — This element occurs in considerable quantity in sea-water combined with 
oxygen as sulphuric acid, forming salts with baryta, strontia, lime, and magnesia. In 
pure sea-water, or in such sea-water as only contains a very small quantity of organic 
matter, no decomposition of the sulphates takes place, and I have kept sea-water for 
many years in well-corked bottles without the least alteration. Near the shores and at 
the mouth of great rivers, where considerable quantities of organic matter are washed 
into the sea, it is easily decomposed, particularly if it is kept in bottles. This decompo- 
sition shows itself always by the production of sulphuretted hydrogen. Water from the 
polar regions is very subject to decomposition, probably on account of a greater quan- 
tity of organic matter than in water from lower latitudes. It is, however, very difficult 
to assign all the different causes which may produce decomposition of sea-water. All 
the water which was brought by the Swedish Spitzbergen Expedition in bottles from 
the polar sea was decomposed, and emitted sulphuretted hydrogen when the bottles 
were opened, while all the water brought from the same sea by the same Expedition 
in tubes of glass, hermetically closed by melting, was undecomposed. Hyperman- 
ganate of potash is the best test for the sulphuretted hydrogen of such water, its colour 
is instantaneously destroyed by the water, and sulphuric acid is formed again. The 
quantity of sulphuretted hydrogen formed in such water differs greatly, and depends, 
at least partly, upon the quantity of organic matter contained in it. Water from the 
Mediterranean is very subject to this kind of decomposition ; but the greatest quantity 
of sulphuretted hydrogen which I have met with in any sample was found in water 
which I owe to Admiral Washington, and which had been taken by Captain Peevost 
of the ‘ Satellite’, under 35° 46' S. lat. and 52° 57' W. long., off the east coast of South 
America, and not very far from the mouth of the Rio de la Plata ; 3000 grains of this 
water destroyed the colour of 455 drops of a solution of hypermanganate of potash, of 
which the same quantity of ordinary sea-water only bleaches four to six drops*. 
* This test has only a relative value in comparing different kinds of water, the quantity of oxygen required 
for complete oxidation being proportional to the quantity of hypermanganate destroyed. 
