The process of separating a crystalloid, from a colloid by filtration, is called: (a) Emulsification (b) Dialysis (c) Coagulation (d) Peptization

Separation techniques are fundamental procedures used in chemistry to differentiate and isolate components of a mixture. One common objective is to purify a particular substance by removing unwanted contaminants. The techniques vary depending on the physical or chemical properties of the substances involved, such as size, state, solubility, and boiling points. Examples include filtration, distillation, evaporation, and chromatography.
Dialysis is a specific kind of separation technique that capitalizes on the differential movement of particles across a semi-permeable membrane. It's commonly used when the aim is to separate small crystalloid particles from larger colloid particles. A semi-permeable membrane acts as a selective barrier, letting some substances, like crystalloids, pass through while blocking colloids.

Understanding the difference between colloids and crystalloids is central to grasping why dialysis works as a separation technique. Colloids are mixtures where one substance is evenly dispersed in another, without dissolving—think of milk or fog. These mixtures have particles larger than those in a solution, typically over 1 nanometer, but under 1 micrometer.

On the other hand, crystalloids consist of smaller particles that are completely dissolved in a solution, like salt in water. These particles can pass through semi-permeable membranes, unlike colloids. This disparity in particle size and the ability to travel through membranes is what dialysis relies on to separate them.

A semi-permeable membrane is a barrier that allows certain substances, and not others, to pass through. It's a key component in the process of dialysis. The membranes are selective based on the size of the particles, their molecular structure, and sometimes their charge.
During dialysis, the semi-permeable membrane enables crystalloids, which are small enough, to diffuse through the membrane, while colloids, being larger, are retained. This selective process facilitates the separation and ensures that the desired purity of the crystalloid substance is achieved. Knowledge of how these membranes function is essential for anyone seeking to understand or utilize the dialysis method in separating chemical mixtures.