[A comparison of efficiency of different auxiliaries used in phosphorus determination by ignition method]

Researches on phosphorus recoveries from NaH2PO4 and (NaPO3)n (n > or = 2) after ignition at temperature from 150 degrees C to 550 degrees C with auxiliary, such as MgSO4, Mg(NO3)2, MgCl2, MgAc2, CaCl2 and so on, were finished. It was found that the phosphorus can not be completely recovered when NaH2PO4 or (NaPO3)n (n > or = 2) was ignited together with MgSO4 at routine ashing temperature (500 degrees C) with the final mixture extracted with 0.2 mol/L HCl at 80 degrees C for 0.5 h. In contrast, MgCl2, MgAc2, Mg(NO3)2 and CaCl2 can all make the phosphorus recoveries completely. MgCl2 (or MgAc2) rather than MgSO4 in the research was suggested. To be utilized as ashing auxiliary in the phosphorus determination with ignition method. Although Mg(NO3)2 is a highly effective auxiliary, yet danger of explosion, toxicity of nitrogen dioxide and more manipulation steps may impede its widespread utilization.