diff --git a/PySDM/physics/constants_defaults.py b/PySDM/physics/constants_defaults.py
index 505511572..c1f890074 100644
--- a/PySDM/physics/constants_defaults.py
+++ b/PySDM/physics/constants_defaults.py
@@ -6,7 +6,6 @@
 """
 
 import numpy as np
-from chempy import Substance
 from scipy import constants as sci
 
 from .constants import (  # pylint: disable=unused-import
@@ -29,13 +28,11 @@
 )
 from .trivia import Trivia
 
-# https://physics.nist.gov/cgi-bin/Star/compos.pl?matno=104
-Md = (
-    0.755267 * Substance.from_formula("N2").mass * si.gram / si.mole
-    + 0.231781 * Substance.from_formula("O2").mass * si.gram / si.mole
-    + 0.012827 * Substance.from_formula("Ar").mass * si.gram / si.mole
-    + 0.000124 * Substance.from_formula("C").mass * si.gram / si.mole
-)
+Md = 28.966 * si.g / si.mole
+"""
+A "twenty-first century" value of dry-air molar mass recommended in
+[Gatley et al. 2008](https://doi.org/10.1080/10789669.2008.10391032)
+"""
 
 # https://web.archive.org/web/20200729203147/https://nucleus.iaea.org/rpst/documents/VSMOW_SLAP.pdf
 # heavy-to-light isotope abundance ratios
@@ -118,9 +115,21 @@
 pH_w = 7
 sgm_w = 0.072 * si.joule / si.metre**2
 
-p_tri = 611.73 * si.pascal
+D0 = 2.26e-5 * si.metre**2 / si.second
+D_exp = 1.81
+
+K0 = 2.4e-2 * si.joules / si.metres / si.seconds / si.kelvins
+
+p1000 = 1000 * si.hectopascals
+c_pd = 1005 * si.joule / si.kilogram / si.kelvin
+c_pv = 1850 * si.joule / si.kilogram / si.kelvin
+g_std = sci.g * si.metre / si.second**2
+
+c_pw = 4218 * si.joule / si.kilogram / si.kelvin
+
+p_tri = 611.657 * si.pascal
 T_tri = 273.16 * si.kelvin
-l_tri = 2.5e6 * si.joule / si.kilogram
+L_tri = 45051 * si.joule / si.mol
 
 # Seinfeld and Pandis, Appendix 16.1, 16A.2
 # default constant values according to Lowe et al. (2019), from ICPM code
@@ -408,6 +417,8 @@ def compute_derived_values(c: dict):
     c["rho_STP"] = c["p_STP"] / c["Rd"] / c["T_STP"]
     c["H_u"] = c["M"] / c["p_STP"]
 
+    c["l_tri"] = c["L_tri"] / c["Mv"]  # 2.5e6 * si.joule / si.kilogram
+
 
 W76W_G0 = -2.9912729e3 * si.K**2
 W76W_G1 = -6.0170128e3 * si.K