National Physical Laboratory of India is realized by using an absolute radiometer. For practical work, a group of tungsten incandescent lamps are used. The level of uncertainty is ± 1.3 × 10. Experimental work has been initiated to realize mole, the SI unit for amount of substance The NPL does not maintain standards of measurements for ionizing radiations. This is the responsibility of the Homi Bhabha Atomic Research Centre, Mumbai. The standards maintained at NPL are periodically compared with standards maintained at other National Metrological Institutes in the world as well as the BIPM in Paris. This exercise ensures that Indian national standards are equivalent
Gas constant "V" is the volume of gas (SI unit cubic metres), "n" is the amount of gas (SI unit moles), "m" is the mass (SI unit kilograms) contained in "V", and "T" is the thermodynamic temperature (SI unit kelvins). "R" is the molar-weight-specific gas constant, discussed below. The gas constant is expressed in the same physical units as molar entropy and molar heat capacity. From the general equation "PV" = "nRT" we get: where "P" is pressure, "V" is volume, "n" is number of moles of a given substance, and "T" is temperature. As pressure is defined as force per unit