Major Inorganic Compound in Fishes
1977 Volume 24 Issue 2 Pages 82-87
Details
1977 Volume 24 Issue 2 Pages 82-87
It was found that major inorganic compound in fishes is not tricalcium phosphate as had been geuerally assumed but is other type of compound which was identified as apatite Ca5(PO4)3 (F, OH). Usually apatite is a solid solution of fluorapatite Ca5(PO4)3 F and hydroxyapatite Ca5(PO4)3 (OH).
Relatively big fishes as tuna contain nearly stoichiometric apatite and small fishes as crucian, saurel and sardine contain apatite with phosphorus in excess. A part of apatite containing phosphorus in excess was gradually decomposed during heating above 600°C to obtain ash, resulting in formation of β-tricalcium phosphate and β-calcium pyrophosphate.
It was found that amount of ash in fishes did not reach constant at 500-600°C, usual temperature based on the official method. Temperature required for obtaining constant amount of ash depended mainly on Ca/P atomic ratio in fishes; it was 900°C with the ratio of about 1.65, 1000°C with the ratio of about 1.5 and higher temperature than 1000°C with the ratio of about 1.25 or smaller.
On heating fishes containing salt, sodium chloride was reacted with a portion of apatite at 1000°C to form β-rehenanite, resulting in volatilization of hydrogen chloride.
