Calcium isolated from various fractions of corals and algae is converted into nitrate and dissolved in a water-ethyleneglycolmonoethylether-dioxane cocktail in the ratio of 1:2:20 using PPO and 1-dimethyl-POPOP as scintillators.45Ca in sea water is counted directly after dilution of 1:10 with water. The carrier capacity of the system is 3 mmole Ca (NO3)2/23ml (120 mg Ca). The counting efficiencies at minimum and maximum carrier concentration are 88,7% and 78,5% respectively. The scintillator solvent system is chemically stable and counts are highly reproducible.