Alkali metal hydrogen double salts can have m ore than one stable phase at ambient temperature. These phases can be identified by the enthalpy and temperature o f the endothermic phase transitions they undergo when heated. Transitions to these phases at am bient temperature depend on mechanical treatment (grinding, one-dim ensional pres sure) as well as on the water vapour pressure above a sample. Eight phase transitions (o f which five were not known before) have been studied by means o f differential scanning calorimetry.It has recently been shown for C sH S04 [1] that solid-solid phase transitions can be created, an nihilated or shifted by mechanical and thermal treatment as well as by varying the water vapour pressure. The most important feature is the occur rence of first order phase transitions due to simple mechanical treatment (grinding or one-dimensional pressing). Here we meet a new type of phase transitions which should not be limited to C sH S 04. Therefore it seemed worthwhile to look for similar transitions in compounds of related composition and structure [2 -6].All samples were crystallized from aqueous solu tions of the corresponding acids and the alkali metal salts. Differential scanning calorimetry (DSC) mea surements were carried out with a commercial Rigaku instrument. If the crystals are simply crushed to a coarse powder, the transitions of interest either do not appear at all, or the results are irreproducible. Combinations of grinding, exposure to water vapour (over pure water at about 393 K or 36.4 wt% H 2S 0 4 at the same temperature) or one dimensional pressure were used to obtain well defined, reproducible first order phase transition peaks. Sometimes repeated grinding and water contact was necessary in order to obtain the transi
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.