OF SEA-WATER IN THE DIFFERENT PARTS OF THE OCEAN. 
211 
carbonate of soda. When the soda was washed away, the remaining substance dissolved 
in muriatic acid, and it could now be proved that alumina was present. The quantity 
of these six-sided pyramids obtained from 6 lbs. of sea-water was, however, so small, 
that no experiments could be made to ascertain whether it contained other substances 
besides alumina. 
I have been somewhat more explicit in relating my experiments to ascertain the exist- 
ence of boracic acid and alumina in sea-water, partly because I found it very difficult to 
find unequivocal proofs of their presence, and partly because it interested me highly to 
find how useful the microscope may be in inorganic analysis, when used in combination 
with chemical tests. 
When I had convinced myself that boracic acid occurred in sea-water, it appeared to me 
in the highest degree probable that the organisms of the sea would collect it, and that it 
might be found in their ashes. I was so fortunate as to begin my experiments with a 
plant that contained it in a rather large quantity, viz. the Zoster a marina. The plant 
was collected in the month of December, at the sea-shore near Copenhagen, dried, and 
burnt. The ashes were washed with water, and the solution, which contained mostly 
chloride of potassium and sulphate of potash, contained also a small quantity of boracic 
acid, probably combined with soda. The insoluble part of the ashes was moistened with 
sulphuric acid until it had a sour taste, evaporated in a moderate heat to dryness, and 
washed with water. When this solution was mixed with strong alcohol and filtered, it 
burned with a green flame, and gave to curcuma paper a brown, and to litmus paper 
a red colour. To separate the boracic acid from the other substances I chose super- 
heated steam, a method to which I was led by a consideration of the way in which 
boracic acid reaches the lagoons of Tuscany. It is well known that this acid comes 
with steam from the interior of the earth, and is condensed when escaping from the 
fumaroles. An experiment in which I mixed dry borax with sulphuric acid, and exposed 
it to the action of superheated steam at 300° to 400° Centigrade, volatilized not only 
boracic acid in form of a solution, but gave even the well-known scales of its hydrate. 
The experiment with the distillation of the ashes of Zostera marina with sulphuric acid 
and superheated steam succeeded completely. The water contained boracic acid, which 
by a slow evaporation was obtained in crystalline scales ; and another portion of it was 
converted into borax, which was obtained in its regular form. Even Fucus vesiculosus 
contains the same acid, but in a much smaller quantity. 
13. Silver. — Malaguti first showed that silver occurs in the organisms of the sea; I 
have subsequently proved it to exist in a coral, a Pocillojoora, and several chemists have 
since tried to prove that silver is precipitated by the galvanic current between the 
copper coating of a vessel and sea-water. If the last determination is confirmed, the 
existence of silver in sea-water is proved by direct experiment. From the Pocillojpora 
alcicornis I have separated it in the following manner : — I dissolved the coral in muriatic 
acid, precipitated the solution by hydrosulphate of ammonia, and dissolved the preci- 
pitate, which consisted of sulphurets, of phosphate of lime, and fluoride of calcium, in 
mdccclxv. 2 G 
