diff --git a/tutorials/compressible/rhoCentralFoam/forwardStep/constant/thermophysicalProperties b/tutorials/compressible/rhoCentralFoam/forwardStep/constant/thermophysicalProperties
index e2ad38ed54..89911f12d8 100644
--- a/tutorials/compressible/rhoCentralFoam/forwardStep/constant/thermophysicalProperties
+++ b/tutorials/compressible/rhoCentralFoam/forwardStep/constant/thermophysicalProperties
@@ -15,8 +15,11 @@ FoamFile
 }
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
-thermoType      ePsiThermo<pureMixture<constTransport<specieThermo<hConstThermo<perfectGas>>>>>;
+thermoType     ePsiThermo<pureMixture<constTransport<specieThermo<hConstThermo<perfectGas>>>>>;
 
+// Note: these are the properties for a "normalised" inviscid gas
+//       for which the speed of sound is 1 m/s at a temperature of 1K
+//       and gamma = 7/5
 mixture         normalisedGas 1 11640.3 2.5 0 0 1;
 
 
diff --git a/tutorials/compressible/rhoSonicFoam/forwardStep/constant/thermodynamicProperties b/tutorials/compressible/rhoSonicFoam/forwardStep/constant/thermodynamicProperties
index 1d7d089e31..d014c6739f 100644
--- a/tutorials/compressible/rhoSonicFoam/forwardStep/constant/thermodynamicProperties
+++ b/tutorials/compressible/rhoSonicFoam/forwardStep/constant/thermodynamicProperties
@@ -15,8 +15,10 @@ FoamFile
 }
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
+// Note: these are the properties for a "normalised" inviscid gas
+//       for which the speed of sound is 1 m/s at a temperature of 1K
+//       and gamma = 7/5
 Cv              Cv [ 0 2 -2 -1 0 0 0 ] 1.78571;
-
 R               R [ 0 2 -2 -1 0 0 0 ] 0.714286;
 
 
diff --git a/tutorials/compressible/sonicFoam/laminar/forwardStep/constant/thermophysicalProperties b/tutorials/compressible/sonicFoam/laminar/forwardStep/constant/thermophysicalProperties
index c504181d21..6558fda69e 100644
--- a/tutorials/compressible/sonicFoam/laminar/forwardStep/constant/thermophysicalProperties
+++ b/tutorials/compressible/sonicFoam/laminar/forwardStep/constant/thermophysicalProperties
@@ -15,9 +15,12 @@ FoamFile
 }
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
-thermoType      ePsiThermo<pureMixture<constTransport<specieThermo<eConstThermo<perfectGas>>>>>;
+thermoType      ePsiThermo<pureMixture<constTransport<specieThermo<hConstThermo<perfectGas>>>>>;
 
-mixture         air 1 11640.31 1.78571 0 0 0.7;
+// Note: these are the properties for a "normalised" inviscid gas
+//       for which the speed of sound is 1 m/s at a temperature of 1K
+//       and gamma = 7/5
+mixture         normalisedGas 1 11640.31 2.5 0 0 1;
 
 
 // ************************************************************************* //