Study Set Content:
Measuring prism
Sample
Illuminating prism
Shadow boundary seen through the telescope
light source
Matted surface
You look in here to make your adjustments and read the refractive index
An eyepiece
Since the Abbe refractometer uses white light and not light of one wavelength (the sodium D line), the white light disperses as it goes through the optics and rainbow-like color fringing shows up when you examine your sample. By turning this control, you rotate some compensation prisms that eliminate this effect.
. Compensation prism adjustment
This is where you put your sample.
Hinged sample prisms.
This provides light for your sample. It’s on a moveable arm, so you can swing it out of the way when you place your samples on the prisms.
Light source
This is a large slotted nut that works itself loose as you move the light source up and down a few times. Always have a dime handy to help you tighten this locking nut when it gets loose.
. Light source swivel arm lock.
You use this knob to adjust the optics such that you see a split field in the eyepiece. The refractive index scale also moves when you turn this knob. The knob is often a dual control; use the outer knob for a coarse adjustment and the inner knob as a fine adjustment.
Sample and scale image adjust
Press this switch, and the numbered refractive index scale appears in the eyepiece. Release this switch, and you see your sample in the eyepiece. Some models don’t have this type of switch. You have to change your angle of view (shift your head a bit) to see the field with the refractive index reading
Scale/sample field switch
This turns the refractometer light source on and off.
Line cord on – off switch
These are often connected to temperature-controlled water recirculating baths. The prisms and your samples in the prisms can all be kept at the temperature of the water.
. Water inlet and outlet.
Factors affecting refractive index
Temperature
Wavelength
Optical Density
For electronic devices such as pH meter, it utilizes a special type of
electrodes
These electrodes used to measure hydrogen ion activity must develop a potential that varies according to the activity of hydrogen ion in a solution () and the other maintains a constant potential called ()
(indicator electrode , reference electrode.
Instrumentation:
pH meter
If two liquids are separated by a pH sensitive (represents the bulb part of the electrode) a certain electrical potential will developed across the membrane. If the solution inside the bulb contains (), the membrane potential may change as the hydrogen ion concentration of the solution varies.
hydrogen ion
Connection to meter
Silver wire coated with AgCl
