Summary Dilute hydrazine hydrate solutions may be readily concentrated to solutions of 65y0 strength by distilling them with an equal weight of xylene until all the hydrocarbon is removed. By beginning with more xylene and distilling similarly, concentrations up to 95- 967c1 but apparently not higher, may be effected in a single operation. Toluene is considerably less efficient than xylene, and benzene is quite unsatisfactory for this ...