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Relationship between the density and the content of HEDP two
2015-07-15 23:08:43

Hydroxy ethylidene diphosphonic acid (HEDP) is a kind of organic phosphate corrosion and scale inhibitors, widely can form a stable complex with various metal ions such as iron, copper, zinc, oxide dissolved metal surface, can play a good sustained release inhibition. Under the high pH value is still very stable, not easy to hydrolysis and decomposition. Acid and alkali resistance, chlorine oxidation resistance and pure HEDP non toxicity in the treatment of circulating cooling water. So it is more important to determine the content of its content. At present, the determination of the active component content of more than 50% of the hydroxy ethyl two (HEDP) method is to follow the national chemical industry standards. This method has good stability, high accuracy and repeatability, but it is complex and has high cost, and it is easy to cause pollution. In a large number of repeated experiments, it is found that the content of HEDP is closely related to the density. After the batch test time, density detection method is simple, convenient, precision, accuracy is also good, stability and repeatability of high, low cost and no pollution to the environment, on the human body without harm, beneficial to the satisfaction of the detection and identification of the actual production needs.

According to the chemical industry standard of total phosphorus of HEDP was measured by gravimetric method, ammonium molybdate points spectrophotometric determination of phosphorus and by iodometric method for the determination of phosphorous, and TP minus is the activity of phosphorus and phosphorous income is HEDP component (expressed by mass fraction). This method is referred to as the following method.

In a constant temperature bath determination HEDP sample into clean, dry cylinder, no bubbles, put the cylinder in 20 DEG of the constant temperature water bath, until the specimen temperature constant, the clean and dry density meter slowly into the sample, and the lower end should be from the bottom of the barrel more than 2cm, not in contact with the cylinder wall. (at this time) the upper end of the density gauge is not allowed to exceed the 2~3 index. To be stable in the sample density meter, scale edge density meter alone under bending is a constant temperature of 20 DEG C, the density of the sample.

The density of the non - acid (HEDP) - two - phosphate acid () sample was compared with that of the standard method.

Table 1 Comparison of the active components and density by the method of determining the elements

Determination of average density of active components by row standard method

123

51.89 51.98 51.91 1.386

52.07 52.31 52.14 1.392

57.63 57.52 57.66 1.442

59.76 59.88 59.85 1.466

Table 2 density and content control table

Density content% density% density%

47 1.390 51 1.430 55 59 1.470

48 1.400 52 1.440 56 60 1.480

49 1.410 53 1.450 57 61 1.490

50 1.420 54 1.460 58 62 1.500

Seen from table 1, the standard method determination of active components and density have certain relation, the qualified product hydroxy ethylidene diphosphonic acid (HEDP) index is the active component is more than or equal to 50 percent, is phosphorus content is less than or equal to 1%, phosphorous content is less than or equal to 3%. According to the repeated experiments, the density of the qualified product HEDP is linear with the active component. Summarize the data experience to draw the corresponding control data see table 2. When the activity of HEDP component is greater than or equal to 50%, is phosphorus content is less than or equal to 1%, phosphorous content is less than or equal to 3% every increase of density 0.001g/cm3 corresponding content has increased by 0.1%. Draw the chart as shown in Figure 1 in figure 2.

In the process of chemical industry standard method, the result of decomposition is fast, the loss of phosphorus is easy, the result is low, too much precipitation is dissolved, the result is low, washing is not clean, the results are too high. But the density method is influenced by many factors, such as temperature, density meter calibration, different factory production process and so on, all of which have a certain effect on the calculation results.
 


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