A storage stable mixture comprising at least 5 wt.-%, based on the total weight of the mixture, of a powderous formulation comprising (i) a compound of formula wherein n is an integer from 1 to 15 R 1 is selected from the group consisting of H, C 1 -C 6 alkyl, phenyl, -OH, -NH 2, -CN, -COOH, -O(C=O)R 8, -NHC(=O)R 8, SO 2 NHR 8, and -ONO 2, and R 8 is C 1 -C 6 alkyl, phenyl, pyridyl such as preferably 2-pyridyl with the proviso that when n is > 3 the hydrocarbon chain may be interrupted by -O- or -NH-, and (ii) silica, and at least 10 wt.-%, based on the total weight of the mixture, of at least one inorganic carbonate, characterized in that the mixture is a premix consisting essentially of and and wherein the weight ratio of the inorganic carbonate to the compound of formula is at least 50, wherein the term 'premix consisting essentially of' indicates that the addition of all wt-% of the listed ingredients of the premix adds up to 100 wt.-% with the proviso, that small amount of impurities or water (moisture) may be present in the powderous formulations in amounts of less than 7 wt. %, preferably less than 5 wt.- %, more preferably less than 3 wt.-%, which impurities/ water (moisture) are introduced via the respective raw materials and which are not added separately. at least 5 wt.-%, based on the total weight of the mixture, of a powderous formulation comprising (i) a compound of formula wherein n is an integer from 1 to 15 R 1 is selected from the group consisting of H, C 1 -C 6 alkyl, phenyl, -OH, -NH 2, -CN, -COOH, -O(C=O)R 8, -NHC(=O)R 8, SO 2 NHR 8, and -ONO 2, and R 8 is C 1 -C 6 alkyl, phenyl, pyridyl such as preferably 2-pyridyl with the proviso that when n is > 3 the hydrocarbon chain may be interrupted by -O- or -NH-, and (ii) silica, and (i) a compound of formula wherein n is an integer from 1 to 15 R 1 is selected from the group consisting of H, C 1 -C 6 alkyl, phenyl, -OH, -NH 2, -CN, -COOH, -O(C=O)R 8, -NHC(=O)R 8, SO 2 NHR 8, and -ONO 2, and R 8 is C 1 -C 6 alkyl, phenyl, pyridyl such as preferably 2-pyridyl with the proviso that when n is > 3 the hydrocarbon chain may be interrupted by -O- or -NH-, and n is an integer from 1 to 15 R 1 is selected from the group consisting of H, C 1 -C 6 alkyl, phenyl, -OH, -NH 2, -CN, -COOH, -O(C=O)R 8, -NHC(=O)R 8, SO 2 NHR 8, and -ONO 2, and R 8 is C 1 -C 6 alkyl, phenyl, pyridyl such as preferably 2-pyridyl with the proviso that when n is > 3 the hydrocarbon chain may be interrupted by -O- or -NH-, and (ii) silica, and at least 10 wt.-%, based on the total weight of the mixture, of at least one inorganic carbonate, characterized in that the mixture is a premix consisting essentially of and and wherein the weight ratio of the inorganic carbonate to the compound of formula is at least 50, wherein the term 'premix consisting essentially of' indicates that the addition of all wt-% of the listed ingredients of the premix adds up to 100 wt.-% with the proviso, that small amount of impurities or water (moisture) may be present in the powderous formulations in amounts of less than 7 wt. %, preferably less than 5 wt.- %, more preferably less than 3 wt.-%, which impurities/ water (moisture) are introduced via the respective raw materials and which are not added separately.