To preliminarily determine the stability of a substance, the following principles can be followed:

Inorganic compounds, as long as they are properly stored and packaged intact, can be used for a long time. However, substances that undergo simple oxidation and deliquescence can only be stored for a short period of time (1-5 years) under dark, shaded, and dry conditions, depending on whether the packaging and storage conditions comply with regulations.

Organic small molecular weight compounds generally have strong volatility, good packaging sealing, and can be stored for a long time. However, simple oxidation, thermal decomposition, simple polymerization, photosensitive substances, etc. can only be stored for a short period of time (1-5 years) under dark, shaded, and dry conditions, depending on whether the packaging and storage conditions comply with the rules.

Organic polymers, especially living materials such as oils, polysaccharides, proteins, enzymes, and peptides, are highly susceptible to the effects of microorganisms, temperature, and light, leading to loss of activity or deterioration. Therefore, they need to be refrigerated (frozen) and stored for a short period of time.

Reference substances, standard substances, and high-purity substances should be stored strictly in accordance with preservation rules, ensuring that the packaging is intact and protected from the influence of chemical environment, and the storage time should not be too long. In general, it is necessary to use reference materials within their validity period.

The stability of most chemicals is still relatively good, and the detailed situation needs to be determined by the actual application requirements. If analyzing data is used as a general understanding, or if there are no specific precise requirements for the analysis results, such as general teaching experiments, general requirements can be made for the quality level of chemical reagents. But the factory's laboratory data is used to guide production, and the quality indicators of chemical reagents must not be confused. In most cases, industrial grade chemical reagents are sufficient for general composition preparation and application. However, in research and the preparation of certain specialty chemicals, in some cases, the quality requirements for raw materials are very strict, and strict control is needed.

In practical application, people are accustomed to using the production date to determine the effectiveness of chemical reagents, which is actually a big fallacy. For example, in a certain higher education institution, I once saw warehouse managers sorting out all chemical reagents that had been out of the factory for more than 2 years and preparing to destroy them, citing that they had already expired. Not to mention causing significant financial waste, the unique plan to destroy hazardous chemicals alone is enough to deter people. Moreover, the acquisition of commercial companies is also prohibited to prevent merchants from "deceiving people".

In general, the effectiveness of chemical reagents should first be judged based on the physical and chemical properties of the reagents themselves, followed by an apparent observation of their preservation status, and then a conclusion on whether they can be used based on detailed requirements.