Single particle size irregular particles

This ideal case is rarely if ever encountered in practice in general there will be a distribution of particle sizes rather than a single size, and in addition there will usually be a range of particle shapes, many of them highly irregular. 

Analysis of discharge particles revealed that both spherical and irregular particles were present, with approximately 1 in 12 spherical. The particle size range was from 3 to 160 pm. The elements detected were aluminum, calcium, chlorine, copper, iron, potassium, magnesium, phosphorus, lead, sulfur, antimony, silicon, titanium, and zinc, with calcium, chlorine, potassium, phosphorus, lead, and silicon the major elements. Antimony and lead did not occur together and none of the samples examined would be confused with FDR particles as their elemental profile differed. A small proportion of the particles containing either lead or antimony met the criteria for single element FDR particles. 

However, it is not easy to evaluate the particle size of a powder. For a large lump, it is possible to measure it in three dimensions. But if the substance is milled, the resulting particles are irregular with different numbers of faces and it would be difficult or impracticable to determine more than a single dimension.For this reason, a solid particle is often considered to approximate to a sphere characterized by a diameter. The measurement is thus based on a hypothetical sphere that represents only an approximation to the true shape of the particle. The dimension is thus referred to as the equivalent diameter of the particle. 

It is not possible to measure or define absolutely the size of an irregular particle, and perfectly regular crystalline solids are rarely, if ever, encountered. The terms length, breadth, thickness or diameter applied to irregular particles are meaningless unless accompanied by further definition, because so many different values of these quantities can be measured. The only meaningful properties that can be defined for a single solid particle are the volume and surface area, but even the... 

Despite these difficulties of definition and measurement it is most convenient for classification purposes, if a single-length parameter can be ascribed to an irregular solid particle. The most frequent expression used in connection with particle size is the equivalent diameter , i.e. the diameter of a sphere that behaves exactly like the given particle when submitted to the same experimental procedure. Several of these equivalent diameters are defined below. 

Sometimes the height of irregularly shaped particles is neglected in this case, the particle length / and width b are determined, these dimensions are then reduced to a single dimension. The concept of equivalent shape and size of particles [107] is used for this purpose. The edge of a cube is such an equivalent dimension for irregularly shaped particles. For particles with projections close to a circle or square (/ Z = 1 1 or 1 2), the equivalent dimension is... 

The complete characterization of a single particle requires the measurement and definition of the particle characteristics such as size, density, shape, and surface morphology. Because the particles of interest are usually irregular in shape and different in surface morphology, there are many different ways and techniques to characterize the particles. Depending on the methods employed, the results may not be completely consistent. Some methods may be more appropriate than others for certain selected applications. 

Shape is of importance with respect to particles because it affects their movement in fluids and among themselves in the absence of a suspending fluid. A particle that has many irregular protrusions on its surface will have different static and dynamic behavior from a particle that is smooth and uniform. Irregular particles will undoubtedly stick together and behave as a single larger particle more readily than spherical or cubic particles. As the size of the particles becomes smaller and smaller, often the importance of shape becomes less. There is thus a relationship between size and shape. 

Since most particulate materials are irregularly shaped, the volumetric response is invaluable, as volume is the only single measurement which can be made of an irregular particle in order to characterize its size. In biological applications the size response is usually left calibrated in volume units (femtolitres, or cubic microns ), but industrially it is conventional to report the equivalent spherical diameter calculated from it. 

Milled lactose particles of the size carrier particle. The carrier serves to increase the flow ability and dosing accuracy. It avoids agglomeration of APIs. In the mixture, the particles adhere to the surface of the carrier as single particles or small agglomerates. During the inhalation process, the API particles are separated from the carrier by impact and the carrier particle deposits within the pharynx. However, the surface of the milled particles is irregular and their size is characterized by a broad distribution. This may lead to uncontrolled disposal of the API [44]. 

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