Why does ammonium oxalate cause swelling of RBCs?

Question

From *Pre examination procedures in laboratory diagnosis* by Walter Guder :> ...It consists of three parts by weight of ammonium oxalate which> causes swelling of erythrocytes balanced by two parts of potassium> oxalate which causes shrinkage...This is regarding use of oxalates as anticoagulants. To me, it makes sense that potassium oxalate causes shrinkage of erythrocytes but i don't understand why Ammonium oxalate causes swelling. Is it because it converts to Ammonia in alkaline pH of blood, diffuses into the RBC and converts back to ammonium.

Answer 1

The ions of the Ammonium Oxalate are diffused through the RBC cell membrane, With a high concentration of ions within the RBC, water diffuses down its concentration gradient( from a high concentration outside the cell to a low concentration inside the cell) into the RBC, causing the RBC to swell.