28. Brass parts with high residual tensile stress at the surface are susceptible to season cracking (i.e. spontaneous cracking occuring on exposure to atmospheric corrosion), if its zinc percentage is more than
55. A machine having assumed life of 20 years is purchased for Rs 32000/-. Its scrap value at the end of its life is Rs 8000/-. If the depreciation is calculated by diminishing balance method, then percentage reduction in its value at the end of first year is __________ percent.
174. Frother is added in the froth floatation cell used in ore beneficiation to stabilise the air bubbles (i.e., froth), which will hold the ore particles, but it does not affect the floatability of minerals. Which of the following is not used as a frother?