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PROFESSOR FORCHHAMMER ON THE COMPOSITION 
always be found ; or when the insoluble remainder from evaporation is heated in a glass 
tube with potassium, it will, when breathed upon, emit the smell of phosphuretted 
hydrogen. 
9. Nitrogen occurs in sea-water combined with hydrogen as ammonia, and its presence 
may be shown by mixing sea-water with a solution of baryta, and distilling the mixture 
in a glass retort. In the distilled portion ammonia may be shown by adding some drops 
of nitrate of protoxide of mercury, which will form grey clouds, or by muriatic acid and 
chloride of platinum, which, when carefully evaporated, will leave the well-known yellow 
salt insoluble in alcohol. It can hardly be doubted that this ammonia is partly formed 
by the living animals of the sea, which exhale ammonia, and partly by the putrefaction 
of their dead bodies. We might ask why we find so small a quantity of ammonia, the 
causes for its formation being so general ; but it is well known that plants will absorb 
it, and that the circulation of nitrogen in the sea is between sea-water, plants, and ani- 
mals, as it is on the dry land between soil, plants, and animals. 
10. Carbon occurs always in the water of the sea, partly as free carbonic acid, partly, 
but in very small quantities, as carbonate of lime, partly in combination with oxygen, 
hydrogen, and nitrogen as organic matter, derived from the destruction of the numerous 
organic beings that live in the sea. It is by the oxidation of these substances that 
the sulphates of sea-water are decomposed, and that the hypermanganate of potash is 
bleached when boiled with sea-water ; and it is owing to these substances that all sea- 
water disoxidizes the peroxide of iron either to protoxide or to sulphuret, and that all 
ferruginous clay or sand deposited in deep sea has a dark colour. 
11. Silicium . — Silica is found in the insoluble remainder from the evaporation of sea- 
water when the salts are dissolved in water. It can be separated from the phosphates 
and fluorides by dissolving in weak muriatic acid, when it remains undissolved along with 
small quantities of sulphate of baryta and strontia. In this state it is easily recognized 
by the blowpipe. In the Sponges it is collected in great quantity ; and when the large 
cyathiform sponge from Singapore is calcined, it leaves a skeleton which retains the 
original form and size of the sponge, and consists almost entirely of silica, the large pores 
of it being lined with oxide of iron, which evidently has belonged to some part of the 
animal itself. It is found also in other animals of the sea, and it occurs in the ashes of 
sea-weeds of the fucoid family, though it is not yet ascertained whether it belongs to 
the fucus itself, or to the infusoria which usually cover its surface. 
12. Boron . — I have long tried to find boracic acid in sea-water, but for a long time 
all my endeavours were vain. Notwithstanding I felt convinced that it must be there, 
since both boracic acid and borates are not very rare, and a great part of its salts 
with lime and magnesia are more or less soluble in water. Thus I thought that water 
from the land must have carried boracic acid into the sea, where it still must be accu- 
mulating, since we do not know any combination by which it could be separated again 
from the water. An additional proof of the correctness of this idea I found in the 
occurrence of Stassfurthite (mostly consisting of borate of magnesia), together with all 
