Table of contents 1 Why is particle size important?

Another common approach to define the distribution width is to cite three values
on the x-axis, the D10, D50, and D90 as shown in Figure 5. The D50, the median, 
has been defined above as the diameter where half of the population lies below this
value. Similarly, 90 percent of the distribution lies below the D90, and 10 percent of 
the population lies below the D10. 
TECHNIQUE DEPENDENCE
HORIBA Instruments, Inc. offers particle characterization tools based on several 
principles including laser diffraction, dynamic light scattering and image analysis. 
Each of these techniques generates results in both similar and unique ways. 
Most techniques can describe results using standard statistical calculations such as 
the mean and standard deviation. But commonly accepted practices for describing 
results have evolved for each technique.
LASER DIFFRACTION
All of the calculations described in this document are generated by the HORIBA laser 
diffraction software package. Results can be displayed on a volume, surface area, 
or number basis. Statistical calculations such as standard deviation and variance 
are available in either arithmetic or geometric forms. The most common approach 
for expressing laser diffraction results is to report the D10, D50, and D90 values 
based on a volume distribution. The span calculation is the most common format to 
express distribution width. That said, there is nothing wrong with using any of the 
available calculations, and indeed many customers include the D4,3 when reporting 
results.
A word of caution is given when considering converting a volume distribution into 
either a surface area or number basis. Although the conversion is supplied in the 
software, it is only provided for comparison to other techniques, such as microscopy, 
which inherently measure particles on different bases. The conversion is only valid 
for symmetric distributions and should not be used for any other purpose than 
comparison to another technique.
figure 5
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