Estimation of Humus in Soil/Manure
Take 20 g soil or manure in a conical flask and add 100 mL of extractant (1:5 ratio). 
Shake well and allow standing for 18 h.   
Filter through Whatman filter paper no. 1 (the residue portion on filter paper is called humin and the filtrate is humus.
It is dark brown in color with pH 13).
To get rid of sodium, the humus is dialyzed in dialysis tubes or parchment paper against running tap water for 24 h.  
It is free of sodium.
Measure the volume, and a known volume (10 mL) is taken in a pre-weighed 100 mL beaker.
The beaker is dried in an oven at 70°C to a constant weight.
The difference in weight gives the amount of humus in 10 mL.
Accordingly, it is calculated on a percentage basis.
