Why is it important to use liquids with relatively lower boiling points when using the Dumas method?

http://web.centre.edu/miles/che135labs/Molecular%20Weight%20by%20the%20Dumas%20Method.pdf

I think its a matter of convenience and precision; i.e., it can be difficult to fill the Dumas tubes with vapor at moderate to high boiling points.

The Dumas method is a technique used for determining the molar mass of a volatile substance. It involves the vaporization of the substance followed by its combustion in a flask. The volume of the vapor is measured and used to calculate the molar mass.

Using liquids with relatively lower boiling points is important for several reasons:

1. Vaporization: During the Dumas method, the volatile substance is vaporized in the flask. Liquids with lower boiling points can easily be converted into vapor at lower temperatures, which ensures efficient vaporization and minimizes the loss of the substance during the process.

2. Ease of combustion: After vaporization, the substance is combusted in the flask to form gaseous products. Liquids with lower boiling points tend to have lower molecular weights, which means they burn more readily. This allows for more complete combustion and accurate measurement of the volume of the combustion products.

3. Evaporation: After the combustion, any remaining liquid needs to be evaporated from the flask to determine the volume of the combustion products accurately. Liquids with lower boiling points evaporate more quickly, making it easier to remove any residual liquid from the flask.

In summary, using liquids with relatively lower boiling points in the Dumas method ensures efficient vaporization, complete combustion, and quicker evaporation, all of which contribute to obtaining accurate and reliable results for determining the molar mass of a volatile substance.