There are a few synonyms for the word "perhamite" that can be considered. One possible synonym for "perhamite" is "saltcake," which is a waste product of the refining process. Another synonym might be "calcium sulfate," which is a mineral often found in sedimentary rocks. Another possible synonym could be "gypsum," which is a mineral that is commonly used in Portland cement. Regardless of which synonym is used, it is important to note that "perhamite" is a relatively obscure term, and may not be familiar to many people outside of specific industries or fields of study.