Fo 
ee =4 
F 
ee 
Mr. Silliman, Jr. on the Composition of Corals. 197 
Organic matter.—This constituent of the corals deserves par- 
ticular notice. Some remarks have already been made on it, 
when speaking of the coloring matter of corals. This organic 
matter is so intimately united throughout the whole structure of 
the corals, amounting to 4 to 8 per cent., that it cannot be separated 
by any method resorted to, except by repeated deflagrations with 
the nitrate of ammonia. When reduced to the finest impalpable 
powder, it may be digested in repeated doses of boiling water, 
until no trace of organic matter is longer found in the water ; and 
yet a careful analysis, by falling short of the amount required to 
complete the 100 parts, will invariably show its presence. The 
oxalate of lime obtained in their analysis, if ignited, (as in the 
usual manner directed for the estimation of lime,) will always 
have a dark carbonaceous hue, derived from the organic matter of 
the coral. 
During the solution of considerable quantities of several corals, 
whose analyses are given beyond, (particularly in No. IV, but 
more or less in all,) a large quantity of fatty (?) matter separated, 
of a yellow color and disagreeable penetrating odor, though not 
fetid. It was easily seen floating on the surface of the solution, 
in transparent jelly-like masses of a yellowish color. It was in- 
soluble in alcohol, but readily so in cold ether, and the evapora- 
tion of its ethereal solution yielded a yellow solid, resembling wax. 
It fuses below 200° F. A pungent irritating odor arose from the 
evaporation of the ethereal solution near its close, which acted 
powerfully on the eyes and nostrils. This volatile principle may 
be analogous to that known to proceed from the decomposition 
of fat, (acrolein?) It deserves more attention than I have been 
able to give it, particularly as it may perhaps be the source of the 
disagreeable odor of some limestones of coral origin. 
Analyses. —The following tables exhibit a comprehensive view 
of the results of the several analyses. The relative proportions 
of organic matter, carbonate of lime, and the complex precipitate 
of phosphates and fluorides thrown down by lime-water, are first 
given; and afterwards the definite composition of this precipitate 
in the nine species more minutely investigated. 
e 
Porites. Porites. Porites. Porites. Porites, 
No. 1 (1). No. 3. \ No. 5. No. 6. 
Carbonate of lime, 95-84 94-412 94-807 93-875 89-864 
Phosphates and fluorides, 205 0-900 0-950 1-561 0.700 
Organic matter, 211 4-688 4-243 4-564 9-431 
