text: Mixtures relying on the use of acid base slushes are of limited practical value beyond producing melting point references as the enthalpy of dissolution for the melting point depressant is often significantly greater (e.g. ΔH -57.61 kJ/mol for KOH) than the enthalpy of fusion for water itself (ΔH 6.02 kJ/mol); for reference, ΔH for the dissolution of NaCl is 3.88 kJ/mol.  This results in little to no net cooling capacity at the desired temperatures and an end mixture temperature that is higher than it was to begin with. The values claimed in the table are produced by first precooling and then combining each subsequent mixture with it surrounded by a mixture of the previous temperature increment; the mixtures must be stacked within one another. 
  Such acid base slushes are corrosive and therefore present handling problems. Additionally, they can not be replenished easily, as the volume of the mixture increases with each addition of refrigerant; the container (be it a bath or cold finger) will eventually need emptying and refilling to prevent it from overflowing. This makes these mixtures largely unsuitable for use in synthetic applications, as there will be no cooling surface present during the emptying of the container.