To prepare the extracting solution in determining the mobile phosphorus and exchange potassium in the soil according to Machigin, it is proposed that the concentration of the desired reagents and working solution be based on the equivalent mass of the NH4⁺ ion, or ammonia NH3. The solution, 0.182 N, should contain 3.1 g/dm3 of NH3 or 3.27 g/dm3 of NH4⁺ and 6.8 g/dm3 of HCO3̄, and a solution with a concentration of 0.200N – 3.54 NH3 or 3.73 g/dm3 of NH4⁺ and 6.3 g/dm3 HCO3̄. When preparing a solution of 0.182 N from the standard ammonium carbonate salt, with an ammonia content of 31%, a sample of 10 g/dm3 is taken. If the salt is partially decomposed, the sample is reduced by 0.12 g for each 1% ammonium less than 31%. If ammonium bicarbonate is used with an ammonium content of 21%, the salt weight should be 8.2 g/dm3. Lack of ammonia up to 31% (0.182 N) or up to 34.5% (0.200 N) is compensated by aqueous ammonia at the rate: NH4OH cm3 = (a×100):(b×n), where a – is the required quantity of ammonia, g; b – ammonium content in aqueous ammonia, %; n – density of aqueous ammonia, g/cm3.