<699> Density of Solids

Type of Posting: Notice of Adoption of Harmonized Standard
Posting Date: 27-Sep-2024
Official Date: 01-Aug-2025
Expert Committee: Excipients Test Methods
Coordinating Pharmacopoeia: European Pharmacopoeia

A bilateral harmonization to the standard for <699> Density of Solids has been approved by the European Pharmacopoeia and the United States Pharmacopeia. The general chapter of <699> Density of Solids has been formally approved by the USP Excipients Test Methods Expert Committee in accordance with the Rules and Procedures of the 2020-2025 Council of Experts.

Major changes from the existing USP–NF General Chapter include:

  1. At the beginning of the chapter, add the general statement to indicate that this is a harmonization chapter: "Portions of the chapter text that are national USP text, and are not part of the harmonized text, are marked with symbols (⧫⧫) to specify this fact."
  2. There are two chapters in the PDG harmonization work plan, "G-19: Density of Solids" and "G-04: Gas Pycnometric Density of Solids". (See a list of general chapters under the PDG workplan through the link here.) However, the USP chapter 〈699〉 covers both of the aforementioned chapters.
    • The entire first part of the current chapter 〈699〉, Terms and Definitions, is replaced with the harmonized standard for "G-19: Density of Solids".
  3. The second part, Gas Pycnometry for the Measurement of Density, remains in the USP chapter 〈699〉 at this time. However, USP will consider splitting this section into a separate chapter based on chapter dependency analysis in the future, as the PDG has a separate harmonized chapter "G-04: Gas Pycnometric Density of Solids". Currently, the European Pharmacopeia has 2.9.23. Gas Pycnometric Density of Solids under their General Monographs section and the Japanese Pharmacopeia has 3.03. Powder Particle Density Determination under their General Tests section.
  4. One of the major updates is to replace the term “true density” with “material density” throughout the chapter. Although the term “true density” is also commonly used in the literature, its usage is quite inconsistent (for example, sometimes reflecting the density measured by gas pycnometry and sometimes being defined as the density for crystalline samples only). Therefore, the term “true density” is not used in this chapter.
  5. Based on the comments received on the Stage 2 proposal published in PF 48(5), in Figure 1, Vc is clarified to be “Entire cell volume”.

Additionally, minor editorial changes have been made to update the chapter to current USP style.

General Chapter <699> Density of Solids will become official from August 1, 2025.

Should you have any questions, please contact Dr. Tong (Jenny) Liu ((240) 221-2072 or jyl@usp.org). For any questions about bilateral harmonization, please see Pharmacopeial Harmonization Group or contact Richard Lew at (240-221-2060 or rll@usp.org).