In this Bureau of Mines study, portions of four acidproof bricks (two red shale and two fireclay) were exposed to 20 wt pct hcl at 90 deg. C for periods of 30 days. Three different techniques were selected to determine volume expansion of these materials after exposure. Linear expansions ranging from about 0.02 to 0.12 pct were noted from ta pin and dilatometer measurements. The use of strain gauges to measure expansions was not successful. The red shale and fireclay bricks with the lowest apparent porosities had the lowest expansions. Expansion data obtained by direct measurement of samples exposed for 30-day periods or by dilatometric measurement of autoclaved samples exposed for 2 h were comparable. This suggests the use of an accelerated autoclave exposure procedure for determining volume expansion effects of ceramic materials in acid environments. This report is based upon work done under a memorandum of agreement between the Bureau of Mines, U.S. Department of the Interior, and the University of Alabama.