question_answer

Give reasons why is platinum iridium alloy used in making prototype metre and kilogram.

Answer:

                  The reasons for making standard kilogram and metre from platinum-iridium alloy are as follows: (i) The alloy is least affected by temperature variations. (ii) It is non-corrosive and so does not wear out easily. (iii) It is quite hard. (iv) It does not change with time.