Quantum-noise reduction in traveling-wave second-harmonic generation

Phosphate rock is digested with molten ammonium bisulfate and between 5 and 16 percent by weight of water to form a solid reaction product. The water is added to the mixture of phosphate rock and ammonium bisulfate either before, during or after the digestion reaction between the phosphate rock and molten ammonium bisulfate. Concentrated phosphoric acid is extracted from the ground, solid reaction product with a nonaqueous, polar, oxygen-containing organic solvent having between one and ten carbon atoms. A phosphoric acid compound or in other words a phosphate is then separated from the solvent either in the form of concentrated phosphoric acid by evaporating the solvent, or in the form of a phosphate salt by adding a base to the extract and precipitating the phosphate salt.