| 摘要 |
PURPOSE:To obtain stably a standard soln. having a highly accurate concn. by adding a prescribed amt. of HCl and tris(hydroxymethyl)aminomethane(Tris) to a mixture composed of a prescribed amt. each of NaCl, KCl and CaCO3. CONSTITUTION:The prescribed amt. each of NaCl, KCl and CaCO3 are put into a tank for prepn. and further a prescribed amt. of HCl is added thereto to complete the reaction CaCO3+2HCl CaCl2+H2O+CO2. Pure water is added thereto to prepare a prescribed amt. of a soln. mixture which is then thoroughly stirred to make uniform the concn. The prescribed amt. of Tris is dissolved in the pure water and is added under stirring into the tank. A surface active agent (for example, ''Toriton X-100'') is finally added thereto and the pure water is added to the soln. to make the entire amt. to the prescribed amt. The NaCl, KCl and CaCO3 which have less hygroscopicity are used as the reagent in the stage of adjusting the sodium ion, potassium ion and calcium ion to the prescribed concn. and therefore the stable and exact weighing is made possible. |
