Use of at least one high-boiling solvent in a mixture comprising at least one (thio)phosphoric acid derivative and at least one volatile component for preventing decomposition or solids formation of the at least one (thio)phosphoric acid derivative in an evaporation process, wherein in said evaporation process the at least one (thio)phosphoric acid derivative is separated from the at least one volatile component and recovered as the bottom product in the form of a mixture comprising as components the at least one (thio)phosphoric acid derivative; and the at least one high-boiling solvent; wherein the at least one high-boiling solvent has a boiling point of at least 130 °C; and wherein the at least one (thio)phosphoric acid derivative is selected from the group consisting of (thio)phosphoric acid triamides according to general formula and (thio)phosphoric acid ester amides according to general formula (IIa) or (IIb); wherein general formula is wherein X 1 is O or S; R 1 is C 1 -C 20 -alkyl, C 3 -C 20 -cycloalkyl, C 6 -C 20 -aryl, C 6 -C 20 -aryl-C 1 -C 4 -alkyl, or C 1 -C 6 -(di)alkylaminocarbonyl; R 2 is H, C 1 -C 20 -alkyl, C 3 -C 20 -cycloalkyl, C 6 -C 20 -aryl, C 6 -C 20 -aryl-C 1 -C 4 -alkyl, or C 1 -C 6 -(di)alkylaminocarbonyl; or R 1 and R 2 together with the nitrogen atom linking them define a 5- or 6-membered saturated or unsaturated heterocyclic radical, which optionally comprises 1 or 2 further heteroatoms selected from the group consisting of N, O, and S; and R 3, R 4, R 5, and R 6 are independently of each other selected from the group consisting of H and C 1 -C 4 -alkyl; and wherein general formula (IIa) is wherein X 2 is O or S; R 7 is C 1 -C 20 -alkyl, C 3 -C 20 -cycloalkyl, C 6 -C 20 -aryl, C 6 -C 20 -aryl-C 1 -C 4 -alkyl, or C 1 -C 6 -(di)alkylaminocarbonyl; and R 8, R 9, R 10, and R 11 are independently of each other selected from the group consisting of H and C 1 -C 4 -alkyl; and wherein general formula (IIb) is wherein X 3 is O or S; R 12 is C 1 -C 20 -alkyl, C 3 -C 20 -cycloalkyl, C 6 -C 20 -aryl, C 6 -C 20 -aryl-C 1 -C 4 -alkyl, or C 1 -C 6 -(di)alkylaminocarbonyl; R 15 is C 1 -C 20 -alkyl, C 3 -C 20 -cycloalkyl, C 6 -C 20 -aryl, C 6 -C 20 -aryl-C 1 -C 4 -alkyl, or C 1 -C 6 -(di)alkylaminocarbonyl; and R 13 and R 14 are independently of each other selected from the group consisting of H and C 1 -C 4 -alkyl. the at least one (thio)phosphoric acid derivative; and the at least one high-boiling solvent; wherein the at least one high-boiling solvent has a boiling point of at least 130 °C; and wherein the at least one (thio)phosphoric acid derivative is selected from the group consisting of (thio)phosphoric acid triamides according to general formula and (thio)phosphoric acid ester amides according to general formula (IIa) or (IIb); wherein general formula is wherein X 1 is O or S; R 1 is C 1 -C 20 -alkyl, C 3 -C 20 -cycloalkyl, C 6 -C 20 -aryl, C 6 -C 20 -aryl-C 1 -C 4 -alkyl, or C 1 -C 6 -(di)alkylaminocarbonyl; R 2 is H, C 1 -C 20 -alkyl, C 3 -C 20 -cycloalkyl, C 6 -C 20 -aryl, C 6 -C 20 -aryl-C 1 -C 4 -alkyl, or C 1 -C 6 -(di)alkylaminocarbonyl; or R 1 and R 2 together with the nitrogen atom linking them define a 5- or 6-membered saturated or unsaturated heterocyclic radical, which optionally comprises 1 or 2 further heteroatoms selected from the group consisting of N, O, and S; and R 3, R 4, R 5, and R 6 are independently of each other selected from the group consisting of H and C 1 -C 4 -alkyl; X 1 is O or S; R 1 is C 1 -C 20 -alkyl, C 3 -C 20 -cycloalkyl, C 6 -C 20 -aryl, C 6 -C 20 -aryl-C 1 -C 4 -alkyl, or C 1 -C 6 -(di)alkylaminocarbonyl; R 2 is H, C 1 -C 20 -alkyl, C 3 -C 20 -cycloalkyl, C 6 -C 20 -aryl, C 6 -C 20 -aryl-C 1 -C 4 -alkyl, or C 1 -C 6 -(di)alkylaminocarbonyl; or R 1 and R 2 together with the nitrogen atom linking them define a 5- or 6-membered saturated or unsaturated heterocyclic radical, which optionally comprises 1 or 2 further heteroatoms selected from the group consisting of N, O, and S; and R 3, R 4, R 5, and R 6 are independently of each other selected from the group consisting of H and C 1 -C 4 -alkyl; and wherein general formula (IIa) is wherein X 2 is O or S; R 7 is C 1 -C 20 -alkyl, C 3 -C 20 -cycloalkyl, C 6 -C 20 -aryl, C 6 -C 20 -aryl-C 1 -C 4 -alkyl, or C 1 -C 6 -(di)alkylaminocarbonyl; and R 8, R 9, R 10, and R 11 are independently of each other selected from the group consisting of H and C 1 -C 4 -alkyl; and wherein general formula (IIb) is wherein X 3 is O or S; R 12 is C 1 -C 20 -alkyl, C 3 -C 20 -cycloalkyl, C 6 -C 20 -aryl, C 6 -C 20 -aryl-C 1 -C 4 -alkyl, or C 1 -C 6 -(di)alkylaminocarbonyl; R 15 is C 1 -C 20 -alkyl, C 3 -C 20 -cycloalkyl, C 6 -C 20 -aryl, C 6 -C 20 -aryl-C 1 -C 4 -alkyl, or C 1 -C 6 -(di)alkylaminocarbonyl; and R 13 and R 14 are independently of each other selected from the group consisting of H and C 1 -C 4 -alkyl. X 2 is O or S; R 7 is C 1 -C 20 -alkyl, C 3 -C 20 -cycloalkyl, C 6 -C 20 -aryl, C 6 -C 20 -aryl-C 1 -C 4 -alkyl, or C 1 -C 6 -(di)alkylaminocarbonyl; and R 8, R 9, R 10, and R 11 are independently of each other selected from the group consisting of H and C 1 -C 4 -alkyl; X 3 is O or S; R 12 is C 1 -C 20 -alkyl, C 3 -C 20 -cycloalkyl, C 6 -C 20 -aryl, C 6 -C 20 -aryl-C 1 -C 4 -alkyl, or C 1 -C 6 -(di)alkylaminocarbonyl; R 15 is C 1 -C 20 -alkyl, C 3 -C 20 -cycloalkyl, C 6 -C 20 -aryl, C 6 -C 20 -aryl-C 1 -C 4 -alkyl, or C 1 -C 6 -(di)alkylaminocarbonyl; and R 13 and R 14 are independently of each other selected from the group consisting of H and C 1 -C 4 -alkyl.