The methods of phosphorus pentoxide in phosphate fertilizer test

The supervision and inspection of the quality inspection department is the key to ensure the quality of the masses of farmers with the quality of phosphate fertilizer. Here I put a few years in phosphate fertilizer (especially an important indicator of phosphorus pentoxide) inspection summed up some experience is summed up as follows, for those and I like in the grass-roots work inspectors for reference.
First of all, in the preparation of QMCA reagent should correctly grasp the amount of citric acid and acetone. In the preparation of QMCA reagent, acetone was added to the main role is improving the settling of the physical properties and the sedimentation of the particles, loose, no adhesion to the wall of the cup, easy washing and filtering. Practice has proved that the amount of acetone can be reduced (but not less than 100 ml), can not be too much. Too much, will make the results of the low; the effect of citric acid added to the is prevent the formation of silicon silicon molybdic quinoline yellow precipitate. In order to eliminate the interference of silicon on the determination of phosphorus. This is mainly due to the presence of citric acid, citric acid and molybdate to form a complex, the dissociation of the complex of the molybdate ion concentration, can make phosphorus generation quinoline phosphomolybdate precipitation, and silicon does not precipitate, thereby eliminating silicon interference. But the amount of citric acid should be appropriate, too much will cause the incomplete precipitation; too small, poor physical properties of precipitation. Therefore, the preparation should be carried out strictly in accordance with the operating procedures.
Secondly, QMCA reagent dosage should be sufficient and appropriate. Practice has proved: 8 mg P2O5 per 10 ml of quinoline molybdenum lemon ketone reagent approximately precipitation, therefore, precipitation can be based on the phosphorus content in the sample due to join QMCA reagent, the amount cut can not be less, so as to avoid the incomplete precipitation, but it should not be too much. QMCA too much dosage in filtering and washing, easy to filtrate white precipitate. Although it does not affect the results, but also a waste.
Third, the operation of the matters needing attention. First, the precipitation temperature can not be too high, the heating can not be too fierce, to micro boiling as a good, otherwise the results have high phenomenon. In sedimentation, filtration and washing process, should prevent from the outside into acid (such as acid or alkali, so as not to affect the results. Is the two generation of Quinoline phosphomolybdate must be precipitation under certain acidity. Practice has proved that in the case of nitric acid concentration of 5%~10% (by volume) can be. The acidity is too low, the precipitation is not complete; the acidity is too high, the physical property of precipitation is poor.
The author believes that our inspector operation should strictly according to the operating rules, and principle and the function of correct understanding on addition of various reagents in detection process, master the correct dosage, it must be for consumers to provide a fair, scientific, accurate detection results.