OF SEA- WATER IN THE DIEEEEENT PARTS OF THE OCEAN. 
245 
There is a more special decomposition of sea-water, which takes place exceptionally, 
but these exceptions are very frequent. They depend upon the organic beings that live 
in the sea, die, and decay in the sea, and are finally dissolved. Of these substances 
that have their origin from organic beings, I have already named ammonia ; but there 
are other substances of organic origin, probably of a more complicated nature, which I 
have observed in the following way. If we pour one or two drops of a solution of 
hypermanganate of potash into fresh sea-water, which has no smell of sulphuretted 
hydrogen, we shall after a short time observe a change in the colour of the liquid, but it 
is hardly more than the first drop that is decomposed so soon after it has been mixed 
with sea-water. The next decomposition goes slower, and is only finished after the 
liquid has been boiled for some time. Now if we pour hypermanganate of potash into 
a very diluted solution of ammonia, it will be completely decomposed by warming the 
mixture to a slight degree. I suppose that the first action upon the hypermanganate 
depends upon the ammonia in sea-water, and the next, which is slower and requires 
boiling and a longer time of action, depends probably upon the other products of spon- 
taneous decomposition of organic matter. Coinciding with these observations is the 
experience that sea-water taken near the surface decomposes a smaller quantity of 
hypermanganate than that which is taken from the depth. If it was ammonia that 
produced the decomposition, there is no reason why there should be less of it near the 
surface than in deep water, since it being combined with a strong acid (either sulphuric 
or muriatic) neither could be volatilized nor oxidized. If it was organic matter, it would 
be oxidized near the surface, on account of the absorbed oxygen of the atmosphere. 
When this organic matter increases in sea-water near the shores, or at the mouth of 
rivers, it will cause a real putrefaction, and attack the sulphates, converting them into 
sulphurets, which again are decomposed by the carbonic acid formed from the organic 
substances at the expense of the oxygen of the sulphuric acid. This sulphuretted 
hydrogen gets free, the carbonic acid will precipitate lime, and a loss of sulphuric acid 
by fermentation will always occasion a loss of lime in sea-water. Putrefaction seldom 
decomposes more than a small quantity of the sulphuric acid present in sea-water, and 
even where it seems to have been very powerful, not one-third part of the sulphuric 
acid has been destroyed. While thus a portion of the sulphates always remains unde- 
composed, there also seems always to remain a portion of the organic matter unoxidized. 
The sulphuretted hydrogen acts instantaneously upon hypermanganates, but when all 
smell of sulphuretted hydrogen has disappeared, there still remains some substance in 
putrefied sea-water which bleaches the hypermanganates when the water is boiled. It 
may be one of the lower oxides of sulphur, or it may be that the organic substance was 
not fully oxidized. 
There is still one general effect of the organic substances dissolved in sea-water, that 
all iron is reduced from peroxide to protoxide, all mud from the deeper parts of the sea 
is dark coloured, either grey, bluish, or green. All Sir James Ross’s deep soundings 
brought blue or green mud or sand to the surface. 
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