212 
PROFESSOR FORCHHAMMER ON THE COMPOSITION 
very weak cold muriatic acid, which left the sulphurets of silver, lead, and copper pro- 
bably mixed with those of cobalt and nickel. These sulphurets were separated from 
the solution, evaporated to dryness with a little nitric acid, to which were added a few 
drops of muriatic acid, and dissolved in water, which leaves sulphate of lead and chlo- 
ride of silver undissolved. When the filter which contained the latter substances is 
burnt, the silver is reduced to metal ; a solution of pure soda will dissolve the sulphate 
of lead and leave the silver, which, when dissolved in nitric acid, can be tested with 
muriatic acid. I obtained from Pocillopora alcicornis about 3,000,000 ? or f rom a solid 
cubic foot of the coral about half a grain of silver. 
14. Copper has not been discovered in sea- water itself, but occurs so frequently in 
the lime-salts of the animals of the sea, and in the ashes of the sea- weeds, that it can be 
discovered with great facility by its well-known tests. In the Pocillopora I found about 
six times more copper than silver, in the coral Heteropora abrotanoides about 3 50*000 
copper, and in the yellowish-green substance which remained after the filtration of the 
muddy sea-water which Sir James Ross had taken in 77° 33' S. lat., it could be shown 
with great facility. Also the ash of Fucus vesiculosus contained copper. 
15. Lead occurs, like copper, in the shells of the animals of the sea and in the ashes 
of sea-weeds, but in greater quantity. In the Pocillopora alcicornis there was found 
about eight times as much lead as silver, and in Heteropora abrotanoides about 50 q 00 
of the coral. It occurs likewise in Fucus vesiculosus. 
16. Zinc. — It has not been shown directly in sea- water, nor could I find it in the 
lime-salts of shells and corals, but it occurs in considerable quantities in the ashes of sea- 
weeds; 400 grains of the ashes of Zostera marina contained 0T39 oxide of zinc = 3 -^ 00 . 
It occurs also in the ashes of Fucus vesiculosus. 
1 7. Cobalt. — I have discovered this metal in the ashes of Zostera marina , and in the 
fossil sponges of the chalk, but not in the large cyathiform sponge of the present sea 
from Singapore. 
18. NicJcel. — We have no such delicate test for nickel as the blowpipe is for cobalt, 
but I have several times observed the well-known brown colour of the solution on pre- 
cipitating the sulphurets of the ashes of sea-weed by hydrosulphate of ammonia, and I 
think we are fairly entitled to suppose that these two metals occur together in sea-water 
as they occur in company in the mineral kingdom. 
19. Iron can be discovered directly in sea-water by evaporating it to dryness and 
dissolving the salts again in water, when it remains insoluble and combined with silica. 
It remains mixed with all the other combinations that are insoluble or difficultly soluble 
in water, but in the solution of these residues in muriatic acid can easily be indicated by 
the common prussiate of potash. It occurs in great quantity in the ashes of sea-weeds 
and the lime-salts of sea animals. 
20. Manganese can be determined directly in sea-water, accompanying the oxide 
of iron separated from a rather large quantity of sea-water, by the application of the 
well-known test for manganese before the blowpipe with carbonate of soda and nitrate 
