So you can place the liquid in a container with standardized markings. Volume can change based on temperature and pressure though. The SI unit of volume is the cubic meter. Other units used can be cubic centimeters, liters, etc. Often we choose the units based on the situation. To use units in an equation though, it's often better to start with SI units. You can convert between units of volume using ratios.
So the syllogism is valid. For a syllogism to be valid, the combined diagram must contain all the information asserted by the conclusion. It may contain more information, but it cannot omit anything. Now let's try a syllogism with a particular premise. Example:
All sound arguments are valid arguments. If an argument is valid, then it must have at least one true premise. Every valid argument is a sound argument. The following is a valid deductive argument: If it snows, then we will go sledding, just like when we were kids. It is snowing. So, certainly we will go sledding, just like when we were kids.