What should be done immediately after the sample is added in the Speedy Moisture Test?

In the Speedy Moisture Test, after the soil sample is added, it is crucial to cap the vessel upside down. This is an essential step because it prevents the escape of any gases released during the reaction. Capping the vessel upside down ensures that the gas stays contained within the apparatus, allowing for accurate pressure readings. This is necessary for determining the moisture content effectively, as the pressure change correlates directly with the amount of moisture in the sample.

The other options do not facilitate this important step of containing the gases released during the reaction. Sealing the vessel tightly could be beneficial, but if done in the wrong orientation, it may not allow for optimal gas retention or could complicate the measurement process. Adding more reagent is unnecessary at that point, as the test requires only the initial sample and reagents mixed. Shaking the vessel may seem helpful, but it could disrupt the conditions needed for an accurate measurement or even result in a loss of gas needed for pressure readings. Overall, capping upside down is the key action needed to ensure the integrity of the test results.