Adding universal cas constant and Boltzmann constant as units of measure.

Author: crystal-growth

src/si/heat_capacity.rs

@@ -167,6 +167,9 @@ quantity! {
         @btu_it_per_degree_fahrenheit: 1.899_100_8_E3; "Btu (IT)/°F",
             "British thermal unit (IT) per degree Fahrenheit",
             "British thermal units (IT) per degree Fahrenheit";
+
+        @boltzmann_constant: 1.380_649_E-23; "k",
+            "Boltzmann constant", "Boltzmann constants";
     }
 }
 

src/si/molar_heat_capacity.rs

@@ -94,6 +94,9 @@ quantity! {
         @electronvolt_per_kelvin_particle: 6.022_140_76_E23 * 1.602_176_634_E-19;
             "eV/(K · particle)", "electronvolt per kelvin particle",
             "electronvolts per kelvin particle";
+
+        @molar_gas_constant: 8.314_462_618_E0; "R",
+            "molar gas constant", "molar gas constants";
     }
 }