Tin pest related problems such as tin whiskers. At 13.2 °C (about 56 °F) and below, pure tin transforms from the silvery, ductile metallic allotrope of β-form "white tin" to the brittle, nonmetallic, α-form "grey tin" with a diamond cubic structure. The transformation is slow to initiate due to a high activation energy but the presence of germanium (or crystal structures of similar form and size) or very low temperatures of roughly −30 °C aids the initiation. There is also a large volume increase of about 27% associated with the phase change to the nonmetallic low temperature allotrope. This frequently makes tin
Anniversary + 200). In Latin, it seems that this rule did not apply precisely for 1½. While "secundus" is Latin for "second", and "bis" for "twice", these terms are not used such as in sesqui-secundus. Instead "sesqui" (or "ses") is used by itself. Many anniversaries have special names. "Etiquette in Society, in Business, in Politics and at Home" by Emily Post, published in 1922, contained suggestions for wedding anniversary gifts for 1, 5, 10, 15, 20, 25, 50, and 75 years. Wedding anniversary gift suggestions for other years were added in later editions and publications; they now comprise what is referred