The correct answer is: D. all of the above
The hydrometer method of sedimentation analysis differs from the pipette analysis mainly in the principle of test, the method of taking observations, and the method of preparation of soil suspension.
In the hydrometer method, a hydrometer is used to measure the specific gravity of the soil suspension at different time intervals. The specific gravity of the suspension decreases as the particles settle out of the suspension. The time it takes for the specific gravity to decrease to a certain value is used to calculate the particle size distribution of the soil.
In the pipette method, a pipette is used to remove a known volume of the soil suspension at different time intervals. The amount of soil in the pipette is then weighed to determine the amount of soil that has settled out of the suspension. The time it takes for a certain amount of soil to settle out of the suspension is used to calculate the particle size distribution of the soil.
The hydrometer method is a more accurate method than the pipette method. However, the hydrometer method is more time-consuming and requires more equipment than the pipette method.
The method of preparation of soil suspension is also different for the two methods. In the hydrometer method, the soil suspension is prepared by mixing a known amount of soil with a known volume of water. In the pipette method, the soil suspension is prepared by mixing a known amount of soil with a known volume of a dispersing agent. The dispersing agent helps to break up the soil aggregates and prevent them from flocculating.
The different methods of preparation of soil suspension can affect the accuracy of the results. The soil suspension should be prepared in a way that minimizes the effects of particle size and shape on the results.