How can scientists measure the total amount of hydrogen in a substance?

Scientists use several analytical methods to determine the total amount of hydrogen in a substance, depending on the nature of the sample:

• Combustion Analysis: A common method involves completely oxidizing the substance in a stream of pure oxygen. This reaction produces water vapour, which is then passed through a dehydrating agent (such as magnesium perchlorate). By measuring the increase in weight of the absorption tube containing the desiccant, the total amount of hydrogen can be calculated.1
• Chemical Titration and Reaction: For acidic hydrogen atoms, scientists can use titration with a strong base, such as sodium hydroxide, to reach a neutralization end point. Weakly acidic hydrogen atoms can be reacted with a Grignard reagent to produce methane, while hydridic hydrogen atoms can be reacted with an aqueous acid to produce molecular hydrogen; in both cases, the resulting gas is measured in a gas buret.1
• Proton Magnetic Resonance: This technique allows scientists to distinguish between different structural types of hydrogen atoms. Because absorption peak intensities are proportional to the number of hydrogen atoms of each kind, this method provides data on the hydrogen content and chemical structure of a compound.1