To preliminarily judge the stability of a substance, the following principles can be followed:
Inorganic compounds, as long as they are properly stored and the packaging is intact, can be used for a long time. However, those substances that are easy to oxidize and deliquescent can only be stored for a short time (1~5 years) under the conditions of avoiding light, shade and dryness, depending on whether the packaging and storage conditions meet the regulations.
Organic small molecular weight compounds are generally more volatile, and the packaging should be well sealed and can be stored for a long time. However, it is easy to oxidize, decompose by heat, easy to polymerize, photosensitive, etc.
Organic polymers, especially life materials such as oils, polysaccharides, proteins, enzymes, and peptides, are highly susceptible to the influence of microorganisms, temperature, and light, and lose their activity, or deteriorate and decay.
In principle, reference materials, reference materials and high-purity substances should be stored in strict accordance with the preservation regulations to ensure that the packaging is intact and avoid being affected by the chemical environment, and the storage time should not be too long. In general, reference materials must be used within the expiration date.
The stability of most chemicals is still relatively good, and the specific situation should be determined by the actual use requirements. If the analysis data is used as a general understanding, or if there are no specific requirements for the accuracy of the analysis results, such as general teaching experiments, the quality level of chemical reagents can be generally required. However, the factory test data is used to guide production, and the quality indicators of chemical reagents must not be ambiguous. In most cases, the chemical reagents used for general synthesis and preparation can be satisfied by using industrial-grade chemical reagents. However, in some cases, the quality requirements for raw materials are very strict and need to be strictly controlled.
In the actual use process, people are always accustomed to judge the effectiveness of chemical reagents by the date of manufacture, but in fact, it is not true. For example, in a certain institution of higher learning, it was once seen that the warehouse manager cleared out all the chemical reagents that had been out of the factory for more than 2 years and prepared to destroy them, on the grounds that they had expired. Not to mention the huge waste of money, the destruction of dangerous chemical goods with different characteristics alone is enough to discourage people. Moreover, commercial companies were not allowed to buy them, so as to prevent them from "deceiving people." This is a sad and sad situation! Later, it was said that a large number of these chemical reagents were "dug deep and buried."
In short, the effectiveness of chemical reagents should first be based on the physical and chemical properties of the chemical reagents themselves, and then the preservation status of the chemical reagents should be observed superficially, and then the conclusions of whether they can be used should be made according to specific needs.