文档介绍：concentration. Such as: mol/L, mol/L and so on. The calibration standard solution concentration, is called determines, it actually is a titration process. In other words, you want acid titration with NaOH, you must first determine the exact concentration of NaOH by titration. General calibration NaOH using potassium hydrogen phthalate. Question: the exact concentrations of potassium hydrogen di-potassium acid then how come is it? it calibrated to do? said it does not need calibration. Can weigh the preparation of standard solutions. Such as potassium hydrogen di-potassium acid substance we call benchmarking. 1. benchmark benchmark: the ability to direct the preparation of calibration standard solutions or substances. Baseline must satisfy the following conditions: sufficient purity. Purity of more than %. Composition consistent with the chemical formula. With crystal water, the content should be consistent with the chemical formula. Stable. That cannot be decomposed in weighing or save time, compounding or moisture absorption. Large molar mass. Molar mass, required amount of weighing, weighing the relative error is smaller. Benchmarks are commonly used: pure metal, such as: Ag, Cu, Fe, Zn and so on; pure compounds such as K2Cr2O7,Na2CO3,Na2C2O4,ZnO, and so on. 2. preparation of standard solutions: direct method: on the analytical balance accurate weighing a certain amount of base material, dissolved in a volumetric flask and diluted to the desired size, then calculate the exact concentration of the solution, such as: K2Cr2O2 preparation of standard solutions. Direct method only applies to the base very clear, otherwise it will result in an error. Preparation of • L-1 solution of Na2S2O3 required in scale 25G solid reagents, such as weighing on reagent in analytical balance, it is not necessary. Preparation and storage solutions can be guided by the following principles: 1. regular and substantial solutions, start preparing about