Also known as chemical reagent or reagent inspection. Mainly used in chemical reactions, analytical tests, research experiments and teaching experiments. Generally divided into general reagents, high-purity reagents, analytical reagents, instrumental analytical reagents, clinical diagnostic reagents, biochemical reagents, inorganic ion chromogenic reagents, etc. There are four commonly used specifications: excellent quality or first-class product (GR, precision analysis and scientific research work); Analyze pure products or secondary products (AR, important analysis and general research work); Chemical pure or three kinds of products (CP, industrial and mining and general chemical experiments in schools); Experimental reagent (low pressure). The content of reference reagent should be 99.9% ~ 100. 1%. With the development of science and technology and emerging industries, the requirements for the purity, purity and accuracy of chemical reagents are becoming more and more strict and professional. It is widely used in analytical chemistry. The grade and specification of reagents should be selected according to specific requirements and uses. In Chinese national standard (GB), general reagents are divided into three grades: the first grade reagent is excellent grade purity, the second grade reagent is analytical grade purity, and the third grade reagent is chemical grade purity. Classification is based on the purity (content), impurity content, purification difficulty and various physical properties of reagents. Sometimes they are classified according to their uses, such as spectrally pure reagents, chromatographically pure reagents and pH standard reagents. In practical work, it is sometimes impossible to obtain reagents with the required purity and need to be purified. Appropriate purification methods should be selected for different reagents. The purification methods are as follows: ① distillation. For volatile reagents, such as commonly used inorganic acids and organic solvents, it is the most commonly used purification method. According to the boiling point, atmospheric pressure or vacuum distillation method is selected. ② sublimation. For some reagents that are easy to sublimate, such as iodine and naphthalene, this method is the simplest. ③ recrystallization. It is suitable for the purification of most solid reagents, and the key is to choose the appropriate solvent. ④ Solvent extraction. The purpose of purification can be achieved by extracting matrix or impurities into organic solvent phase. ⑤ ion exchange chromatography separation. It is a new and efficient purification method, such as adsorption of iron (FeCl4-) from hydrochloric acid with anion exchange resin. In addition, there are special means such as thin layer chromatography, electrodialysis, zone melting and ion exchange membrane to separate and purify chemical reagents. Pharmaceutical excipients (pharmaceutical excipients) refer to all medicinal materials added to the prescription except the main medicine in order to solve the formability, effectiveness, stability and safety of the preparation when designing the prescription. The essence of prescription design of pharmaceutical preparations is the process of screening and applying pharmaceutical excipients according to the characteristics of drugs and the requirements of dosage forms. Pharmaceutical excipients are the basic materials and important components of pharmaceutical preparations, the material basis for ensuring the production and development of pharmaceutical preparations, and play a key role in the formulation and production of pharmaceutical preparations. It not only endows drugs with specific dosage forms. But also has a great relationship with improving the curative effect of drugs and reducing adverse reactions. The reliability and diversity of its quality are the basis to ensure the advanced dosage forms and preparations. The above are the concepts of reagents and pharmaceutical excipients found on Baidu for reference. Generally speaking, hydrochloric acid added to the preparation for adjusting PH value should belong to the category of excipients.