combined gas equation

diff --git a/chem/gas.md b/chem/gas.md
index 4cd56892b7d97249ab35cd5b85d47ba76562e2ad..1848d3885a4a7490e52e259d177d933c513f2dd2 100644 (file)
--- a/chem/gas.md
+++ b/chem/gas.md
@@ -1,5 +1,9 @@
 # Gases
 
+## Comibned gas equation
+
+$${P_1 V_1 \over T_1} = {P_2 V_2 \over T_2}$$
+
 ## Perfect gas equation
 
 $$PV=nRT$$