ISO 3838:2004规定了原油和作为液体处理的石油产品密度或相对密度的测定方法。 毛细管塞比重瓶法也适用于固体，该方法也可用于煤焦油产品，包括道路焦油、杂酚油和沥青，或用于这些与石油产品的混合物。根据ISO 3007，本方法不适用于测定里德蒸气压大于50 kPa或初始沸点低于40℃的高挥发性液体的密度或相对密度。 建议使用刻度双毛细管比重瓶法准确测定除粘性较大的产品外的所有产品的密度或相对密度，当只有少量样品可用时，该方法特别有用。根据ISO 3007，该方法仅适用于里德蒸汽压力为130 kPa或以下且在试验温度下运动粘度小于50厘的液体。 为测定高挥发性液体的密度或相对密度，规定了特殊预防措施。

ISO 3838:2004 specifies methods for the determination of the density or relative density of crude petroleum and of petroleum products handled as liquids. The capillary-stoppered pyknometer method is also for use with solids and this method may also be used for coal tar products, including road tars, creosote and tar pitches, or for mixtures of these with petroleum products. This method is not suitable for the determination of the density or relative density of highly volatile liquids having Reid vapour pressures greater than 50 kPa according to ISO 3007 or having an initial boiling point below 40 degrees Celsius. The graduated bicapillary pyknometer method is recommended for the accurate determination of the density or relative density of all except the more viscous products, and is particularly useful when only small amounts of samples are available. The method is restricted to liquids having Reid vapour pressures of 130 kPa or less according to ISO 3007 and having kinematic viscosities less than 50 mm²/s (50 centistokes (cSt)) at the test temperature. Special precautions are specified for the determination of the density or relative density of highly volatile liquids.