Twelve different acid-proofing Mortar compositions were tried and tested for compressive strength. The composition containing quartz powder 50 gin, sand 20 gin, sodium fluosilicate 2 gm, and sodium silicate (30 Be) solution 32 ml gave the highest compressive strength of 1710 psi after 7 days. The results confirm of ASTVI specification (1961, 4 No. 421).