Another common metal that experiences an allotropic change is tin.White (or ) tin, having a body-centered tetragonal crystal structure at room temperature, transforms, at C ( F), The rate at which this change takes place is extremely slow;however,the lower the temperature (below C) the faster the rate.Accompanying this white tin-to-gray tin transformation is an increase in volume (27 percent), and, accordingly, a decrease in density (from 7.30 g/cm3 to 5.77 g/cm3). Consequently,this volume expansion results in the disintegration of the white tin metal into a coarse powder of the gray allotrope. For normal subambient temperatures, there is no need to worry about this disintegration process for tin products, due to the very slow rate at which the transformation occurs. This white-to-gray-tin transition produced some rather dramatic results in 1850 in Russia.The winter that year was particularly cold, and record low temperatures persisted for extended periods of time.The uniforms of some Russian soldiers had tin buttons,many of which crumbled due to these extreme cold conditions, as did also many of the tin church organ pipes. This problem came to be known as the “tin disease.” to gray (or ) tin,which has a crystal structure similar to diamond (i.e., the diamond cubic crystal structure); this transformation is represented schematically as follows: Specimen of white tin (left).Another specimen disintegrated upon transforming to gray tin (right) after it was cooled to and held at a temperature below C for an extended period of time. (Photograph courtesy of Professor Bill Plumbridge, Department of Materials Engineering,The Open University, Milton Keynes, England.)