In these instruments, prism or grating is used for monochromtizing the light and the measurements can be made at any desired wavelength within the spectral region of the instrument. In the visible region instruments, the optical system consisting lenses and prism is made up of ordinary glass whereas in the ultraviolet region quartz must be used. Deuterium or hydrogen lamp for U.V. range 200-250nm and the tungsten lamp for the visible range 320-1100nm is source of light. It can determine the dissociation constant of an indicator, Examples of indicator are methy red and bromophenol blue.

Polarimeters are instruments which measure the rotation of the plane of polarization in certain liquids. The classical instrument is optical device. It has many short comings. It needs a dark room, sodium light and strains the eyes. All these short comings are removed in Digital polarimeter.

Colorimeter is an instrument used to measure concentration of a substance in a solution. It is based on Beer Lambert law. The color development is proportional to concentration of the dissolved substance under test, hence absorption of light in the sample is proportional to concentration. The visible region of spectrum is from 400nm to 700nm. We have used 8 filters to cover the entire visible region.

The simplest form of a potentiometer consists of thin uniform resistance wire, stretched over a scale one meter long graduated in millimeter. Now a days metre wire is replaced by a series of coils of standard resistance and a circular 2 ohms slide wire graduated in milli volts. Results are displayed in milli volts on a direct digital readout by emitting diodes. It has four types of electrodes. They are platinum electrode, glass electrode, silver electrode and reference electrode.

The basic principle of TLC is similar to that of column chromatography, the difference being that in place of the adsorbent in the column it is coated glass plate which acts life adsorption column. Identification and separation by TLC can be carried out very quickly in a few minutes. The choice of stationary phase is very wide. Any of the materials like alumina, silica gel, kiesselguhr, cellulose, acetylated cellulose etc many be used for preparing thin layers. The separated components can be recovered with grater ease, scraping the layer with a knife and dissolving. The substance in a suitable solvent.

Electrically heated ovens are commonly used in the laboratory to remove water and other solvents from chemical samples. If it also used to dry laboratory glassware. Laboratory ovens rarely have a provision for preventing the discharge of the substances volatized in them. Oven should not be used to dry any chemical sample that might pose a hazard because of acute or chronic toxicity to avoid explosion, glassware. That has been rinsed with an organic solvent should be rinsed being dried in an oven.

The PH value is Measure of the Hydrogen ion concentration and is defined by the following equation.

PH=log 10(1)
H+

1. Display : 4 digit LED

2. Range : Conductance = 0.1 Mho to 1000 MMhos in 5 ronges, 0-200 uMhos, 2 MMhos, 20 MMhos, 200 MMhos, 1000MMhos- Resistance = 0.1O Ohm to 2 M ohm in 5 ranges, 0 to 2000 . 2 K.

3. Accuracy : Conductance = + 0.5% of range + 1 digit.

4. Resistance : + 0.5% of range + 1 digit

5. Supply : 220/230 volts + 10% 50 Hz A.C. built in stabilizer. (Supplied with conductivity's cell, Dust cover and instruction manual)

• Automatic temp. compensation facility with PT-100 sensor.

• Temperature Indication Facility 0 to 100 C.

• Recorder output facility.

• Spare conductivity cell