Ch 34: Preparing Samples for Analysis Flashcards
This changes the composition of the sample (e.g. the loss of volatile compounds, increase in water content, and reacting with the atmosphere)
Crushing or grinding
a device for grinding solids that are not too hard
Ball mill
A device that moves along three axes for vigorous grinding of samples
Mixer or mill
A device used for crushing hard, brittle materials
Plattner Diamond Mortar
Two forms of water in solid state
Essential and Non-essential Water
Is the water that is an integral part of the molecular or crystalline structure of a compound in its solid state
Essential Water
Example of essential water
solid hydrate/ hydrate salt
The water that is formed when a pure solid is decomposed by heat or other chemical treatment
Water of Constitution
The water that is physically retained by a solid as a consequence of physical forces
Nonessential water
Types of Nonessential water
Adsorbed water, Sorbed water, Occluded water
Type of nonessential water that resides on the surface of the particles of a material
Adsorbed water
The amount of water adsorbed on a solid _______ as the temperature of the solid ___________, eventually approaches 100 C.
decreases, increases
Surface chemistry of moisture usually occurs rapidly, with equilibrium being reached after 5 - 10 mins only
Adsorption
A type of nonessential water that is contained within the interstices of the molecular structure of a colloidal compound
Sorbed water
Surface chemistry of moisture usually takes time, reaching equilibrium for days or even weeks
Sorption
This contributes well to the overall mass of solid samples, which may appear as dry powders
Sorbed water
A nonessential water that is trapped in random microscopic pockets of solids, particularly minerals and rock
Occluded water
Is not in equilibrium with the atmosphere and is insensitive to humidity
Occluded water
The ratio of the vapor pressure of water in the atmosphere and the vapor pressure in air saturated with water
Relative humidity
A process in which a crystalline material containing occluded water suddenly explodes during heating due to the buildup in internal pressure, resulting to steam formation
Decrepitation
The mass of the water adsorbed on a typical solid is plotted against the partial pressure of water in the surrounding atmosphere
Adsorption Isotherm
