Crystal-habit microscopy

Morphology/crystal habit Microscopy/image analysis Scanning electron microscope... 

Differential Scanning Calorimeter (DSC) was used by Rogers and Dinegar [165] in combination with X-ray and microscopy to find the reason for ano-lous behaviour in the heat of fusion of PF.TN crystallized by different meth- . Microscopy revealed the existence of at least three crystal habits of PETN ) ctragonal (2) needle, (3) irregular plates. Their heats of fusion A//t were ... 

Crystal morphology SEM or optical microscopy Compare crystal habits and levels of agglomeration... 

Particle size analysis should be carried out on all batches of salt candidates to establish suitable recrystallization procedures. A rapid assessment of both the particle size and crystal habit can be carried out by Scanning Electron Microscopy (SEM). Laser diffraction techniques can provide a rapid assessment of the particle size distribution using less than lOmg of material. It is also useful to retain a photomicrograph for each batch. 

The optical microscopy investigation shows some significant differences in mean diameter and crystal habit due to crystallization conditions. 

Preliminary X-ray experiments indicate that the pendant chloro groups are organized in a highly ordered array and that the distance between these groups can be measured [37]. Additionally, several crystal habits, such as spherulites and dendrites, were observed by optical microscopy, upon precipitation of this polymer from a dilute toluene solution. 

The simplest method is optical microscopy, in which visible light (photons) is used to observe a sample. It has a resolution limit around 0.25-0.5 pm, which is on the order of 2/2, where 2 is the wavelength of incident light. From a strict colloid science point of view, it lies near the upper limit of colloid particle sizes and appears to be of limited utility. However, it is of great help in the identification of minerals, because it allows observation of crystal habits (the shape and size of crystals, which are determined by their internal symmetry). With experience, many minerals can be identified in a soil sample under a microscope, even from simple inspection. A unique feature of optical microscopy is the availability of polarized light, which is handy in distinguishing minerals or even different crystal types of the same compound (Bullock et al. 1985 Cady, Wilding, and Drees 2010). 

The habit of pharmaceutical compounds has been used for purposes of identification, although the method can only be reliably used when the crystallization solvent used to generate the test crystals is carefully controlled. Since the faces of a crystal must reflect the internal structure of the solid, the angles between any two faces of a crystal will remain the same even if the crystal growth is accelerated or retarded in one direction or another. Toxicologists have made extensive use of microscopy following multiple recrystallization, and they have developed useful methods for compound identification [5]. 

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