present in the Waters of the. Baltic. 349 
cipitate collected and washed. The whole precipitate, which 
contains carbonate, sulphate and phosphate of lime, fluoride 
of calcium, silica, and magnesia, was redissolved in muriatic 
acid, which left the greater part of silica undissolved. The 
solution was mixed with muriate of ammonia, and a second 
time precipitated by an excess of ammonia. This precipitate 
from 100 lb. of sea-water weighed 3°104 grains, and con- 
sisted of phosphate of lime and fluoride of calcium. It was 
divided into two equal parts, of which the one was in a platina 
crucible mixed with concentrated sulphuric acid, and allowed 
to act on a slip of glass, covered with wax, in which some 
words were scratched with a copper needle. The glass was 
most decidedly etched, but the words appeared more clear 
and legible if breathed upon. The second half part was 
likewise mixed with sulphuric acid, but in a bent tube, and 
distilled into a smal] vessel which contained a weak solution 
of ammonia. The tube was etched, and the vessel contained 
precipitated silica. It was thus completely proved that sea- 
water contains fluoride of calcium, but the quantity in 100 
lb. sea-water from the Sound, at Copenhagen, can hardly ex- 
ceed half of a grain, or since the proportion of the different 
salts varies very little in sea-water, it will be about 1 grain 
in 100 lb. of water of the ocean, which contains between 3-5 
and 4 per cent. of salts. 
All the residuums from the trials to find fluorine were 
dissolved in muriatic acid, and thrown down by an excess of 
ammonia. The precipitate, washed, dried, and heated, was 
mixed with potassium in a glass tube [and heated] until the 
excess of potassium was driven off. The lower part of the 
tube was cut off and thrown into water, where it, for hours, 
continued to give out small bubbles, distinguished by the pe- 
culiar smell of phosphuretted hydrogen, although they did 
not inflame by themselves. Thus, the existence of phosphoric 
acid was likewise proved, although I could not try the de- 
lieate test for phosphoric acid which we owe to Mr Svanberg, 
it not being known at the time when I made my experi- 
ments. 
‘Th all the different species of corals which IT have ana- 
lysed, I likewise found fluorine. 
