Anhydrous sodium hydroxide: the heat content from 0 degrees to 700 degrees C, the transition temperature, and the melting point

Abstract

Samples of sodium hydroxid e, whose purity a s indicated by anal.vses was approx i mal ({,. 99.3 percent, we re scaled in pure sil ver. Cryoscopic mcas urements indicated a trans iti on t e mperature of 293° C. U sin g a " drop" method and a Bun sen icc calorimeter, Lhe en tha lp~' 1 change bet\\'een 0 ° and each of 11 temperatu res up to 700° C was meas l11'ed. \~T il h r eason-able s implifying a ss ump t ion s, t hc t hermal measurements near t he fre ez ing poin t were lI sed t o correct for the impuri ty, giving for pure sodium hydroxide a m eltin g point of 3 19 ° C and the same ,·alue, 159 abso lu te joules per gram, for t he heat of fu s ion and thc heat of transit ion. The heat capacity deri ved for the liquid is es timated to be cor rect wi t hi ll 2 pe rce llt , wh e rea s the derived heats of fu s ion and transiti on ma.v be in elTor by as much as 5 pe rce nt. Va lllcs of 11cat capaci t.v , en trop y, rela! i ve e n thalpy, and r e lat i" e fr ee cnerg.'· arc t abula Led at Tcgular in t(' J'val s from 298 ° t o 1,000 ° I\:.