In a laboratory setting, chemicals are often categorized into different grades based on their quality and purity, following is the common practice for chemical categorization. However, it's important to note that the specific definitions and requirements for these grades may vary slightly depending on the country, organization, or manufacturer. Therefore, it is advisable to consult the supplier or refer to the relevant standards or specifications to ensure the suitability of the chemicals for a particular application.

• Guaranteed Reagent: Guaranteed Reagent (GR) is a high-quality grade of chemicals that typically meets strict specifications and has a high level of purity. These chemicals are commonly used in research and analytical laboratories where precise and accurate results are required. Guaranteed Reagent chemicals are often accompanied by detailed specifications and quality control information.

• Extra Pure : Extra Pure (EP) reagents are suitable in qualitative, semi quantitative analysis, organic synthesis and general use in laboratory. This grade complies with critical tests of raw material used in API, agrochemicals and Specialty chemicals.

• Analytical Grade: Analytical Grade chemicals/reagents (AR) are of the highest purity among the commonly available grades. They are specifically designed for analytical applications, such as qualitative and quantitative analysis, where the presence of impurities can significantly affect the results. Analytical Grade chemicals have stringent purity requirements, typically above 99.9%, and are free from known impurities that could interfere with analytical measurements.

• Chemical Pure: Chemical Pure (CP) grade reagents with purity suitable in general applications.

• ACS grade, which is usually equal to Reagent Grade (RG) meets or exceeds purity standards set by the American Chemical Society (ACS). This grade is acceptable for food, drug, or medicinal use and can be used for ACS applications or for general procedures that require stringent quality specifications and a purity of ≥95%.

• Laboratory Grade: Laboratory Grade chemicals/reagents (LR) are commonly used in general laboratory experiments and applications where high precision is not critical. While they have lower purity requirements compared to Analytical Grade chemicals, Laboratory Grade chemicals still meet recognized standards for general laboratory use. They typically have a purity level of above 95% and may contain some impurities that are not expected to significantly impact most laboratory procedures.

• USP/NF Grade: This classification is specific to chemicals used in the pharmaceutical industry. United States Pharmacopeia (USP) and National Formulary (NF) grades ensure that the chemicals meet the standards set by these organizations for pharmaceutical use. These chemicals have high purity levels and are suitable for manufacturing drugs and other pharmaceutical products.

• Technical Grade: Technical grade chemicals are used in industrial applications and manufacturing processes where high purity is not always necessary. They typically have a lower level of purity compared to laboratory or pharmaceutical grades and may contain impurities that do not interfere with their intended use.

• Industrial Grade: Industrial grade chemicals are primarily used in large-scale industrial applications and manufacturing processes. They may have varying levels of purity depending on the specific requirements of the industry but are generally not as pure as laboratory or pharmaceutical grades.

• Commercial Grade: Commercial grade chemicals are commonly available chemicals found in consumer products or sold for general use. They may have lower purity levels compared to other grades and may contain a higher concentration of impurities.

It's worthy noting that Laboratory Grade is suffice for most situation in Secondary School Science Experiment.

在實驗室環境中，化學品通常會根據其品質和純度分為不同的等級，以下是化學品分類的常見做法。 然而，值得注意的是，這些等級的具體定義和要求可能會因國家、組織或製造商的不同而略有不同。 因此，建議諮詢供應商或參考相關標準或規範，以確保化學品適合特定應用。

• 保證試劑：保證試劑 (GR) 是一種高品質等級的化學品，通常符合嚴格的規格並具有高純度。 這些化學品通常用於需要精確結果的研究和分析實驗室。 有保證的試劑化學品通常附有詳細的規格和品質控制資訊。

• 特純：特純 (EP) 試劑適用於定性、半定量分析、有機合成和實驗室一般用途。 此等級符合 API、農業化學品和特種化學品中使用的原料的關鍵測試。

• 分析級：分析級化學品/試劑 (AR) 是常用等級中純度最高的。 它們專為分析應用而設計，例如定性和定量分析，其中雜質的存在會嚴重影響結果。 分析級化學品具有嚴格的純度要求，通常高於 99.9%，且不含可能幹擾分析測量的已知雜質。

• 化學純度級：化學純度級（CP）試劑，純度適合一般應用。

• ACS 級別通常等於試劑級 (RG)，符合或超過美國化學會 (ACS) 制定的純度標準。此等級可用於食品、藥品或醫藥用途，可用於 ACS 應用或需要嚴格品質規格，純度 ≥95%。

• 實驗室級：實驗室級化學品/試劑 (LR) 通常用於精度要求不高的一般實驗室實驗和應用。 雖然與分析級化學品相比，它們的純度要求較低，但實驗室級化學品仍然符合一般實驗室使用的公認標準。 它們的純度通常高於 95%，可能含有一些預計不會對大多數實驗室程序產生重大影響的雜質。

• USP/NF 等級：此分類特定於製藥業使用的化學品。 美國藥典 (USP) 和國家處方集 (NF) 等級確保化學品符合這些組織制定的製藥用途標準。 這些化學物質具有高純度，適合製造藥物和其他醫藥產品。

• 技術級：技術級化學品用於並不總是需要高純度的工業應用和製造過程。 與實驗室或製藥級相比，它們的純度通常較低，並且可能含有不影響其預期用途的雜質。

• 工業級：工業級化學品主要用於大規模工業應用和製造過程。 根據行業的具體要求，它們可能具有不同的純度水平，但通常不如實驗室或製藥級純度。

• 商業級：商業級化學品是消費品中常見的或一般用途出售的化學品。 與其他等級相比，它們的純度可能較低，並且可能含有較高濃度的雜質。
  
  需要注意的是，這些類別可能會因特定行業、地區或監管標準而略有不同。 因此，始終有必要參考製造商或監管機構提供的特定分級系統或標準，以獲得有關特定化學品純度的準確資訊。

值得注意的是，實驗室等級足以滿足中學科學實驗中的大多數情況。

純度表示

當選擇化學品時需要注意的是，表達物質成分或純度的具體方法可能會根據所使用的環境、產業或分析技術而有所不同。 因此，需要參考具體所遵循的標準，才能準確理解所用等術語的含義。

例子 : 碳酸鎂 AR 40-45% MgO basis vs 碳酸鎂 99.99% Metal Basis

MgO Basis: 當碳酸鎂以 MgO 基表示時，表示該物質的成分或純度以其氧化鎂 (MgO) 含量來報告。 在這種情況下，報告的值表示如果碳酸鎂完全轉化為氧化鎂則將獲得的MgO的量。 此方法通常在分析或報告碳酸鎂樣品的成分時使用。

• 氧化鎂 (MgO) 是一種由一個鎂原子與一個氧原子鍵結而成的化合物。

• 碳酸鎂（MgCO3）可熱分解產生氧化鎂和二氧化碳。 分解反應如下：MgCO3 → MgO + CO2。.

• 當以 MgO basis 為基準表示碳酸鎂的組成時，假定碳酸鎂全部轉化為氧化鎂。 報告的值表示如果發生完全轉換則將獲得的 MgO 的百分比或重量。

• MgO 基通常用於各種行業，包括化學製造、製藥和分析化學。

Metal Basis: 另一方面，當碳酸鎂以金屬基表示時，是指基於其總金屬含量的物質的成分或純度。 對於碳酸鎂，感興趣的金屬是鎂 (Mg)。 報告值代表碳酸鎂化合物中存在的鎂的量，無論其特定形式或化合物如何。.

• Metal basis 表示物質基於其總金屬含量的組成或純度，無論其可能處於何種特定化合物或形式。

• 就碳酸鎂而言，Metal basis 是指化合物中存在的鎂 (Mg) 量，無論其是碳酸鎂 (MgCO3) 或氧化鎂 (MgO) 形式。.

• 當重點特別集中在化合物的金屬成分上時，以金屬為基礎表達組合物是有用的。

• Metal basis 在冶金、材料科學和金屬製造等行業中非常重要，其中金屬的表徵和分析至關重要。

選擇以 MgO basic 或 Metal basic 基表示成分取決於所涉及的應用或行業的背景、目的和特定要求。 當遇到這些術語時，了解其含義和上下文以準確解釋成分或純度非常重要。

Purity representation

It's important to note that the specific method of expressing the composition or purity of a substance can vary depending on the context, industry, or analytical technique being used. Therefore, it's always necessary to refer to the specific context or standard being followed to understand the meaning of terms like "MgO basis" or "metal basis" accurately.

Example : Magnesium Carbonate AR 40-45% MgO basis vs Magnesium Carbonate 99.99% Metal Basis

MgO Basis: When magnesium carbonate is expressed on an MgO basis, it means that the composition or purity of the substance is reported in terms of its magnesium oxide (MgO) content. In this case, the reported value represents the amount of MgO that would be obtained if the magnesium carbonate were completely converted to magnesium oxide. This method is commonly used when analyzing or reporting the composition of magnesium carbonate samples.

• Magnesium oxide (MgO) is a compound that consists of one magnesium atom bonded to one oxygen atom.

• Magnesium carbonate (MgCO3) can be thermally decomposed to produce magnesium oxide and carbon dioxide. The decomposition reaction is as follows: MgCO3 → MgO + CO2.

• When expressing the composition of magnesium carbonate on an MgO basis, it assumes that all the magnesium carbonate is converted to magnesium oxide. The reported value represents the percentage or weight of MgO that would be obtained if complete conversion occurred.

• The MgO basis is often used in various industries, including chemical manufacturing, pharmaceuticals, and analytical chemistry, when discussing or analyzing magnesium carbonate.

Metal Basis: On the other hand, when magnesium carbonate is expressed on a metal basis, it refers to the composition or purity of the substance based on its total metal content. In the case of magnesium carbonate, the metal of interest is magnesium (Mg). The reported value represents the amount of magnesium present in the magnesium carbonate compound, regardless of the specific form or compound it may be in.

• The metal basis expresses the composition or purity of a substance based on its total metal content, irrespective of the specific compound or form it may be in.

• In the case of magnesium carbonate, the metal basis refers to the amount of magnesium (Mg) present in the compound, regardless of whether it is in the form of magnesium carbonate (MgCO3) or magnesium oxide (MgO).

• Expressing the composition on a metal basis is useful when the focus is specifically on the metal component of the compound.

• The metal basis can be important in industries such as metallurgy, materials science, and metal manufacturing, where the characterization and analysis of metals are essential.

The choice of expressing the composition on an MgO basis or metal basis depends on the context, purpose, and specific requirements of the application or industry involved. It's important to understand the intended meaning and context when encountering these terms to interpret the composition or purity accurately.