Depending on this, the appropriate equipment is selected (in the first case a hammer mill is needed, in the second case a ball mill). The type of roots is also important: one type of machine is used for fibrous roots and another for non-fibrous roots. It is also necessary to take into account the moisture content of raw materials: raw materials must necessarily be dried to a residual moisture content of 6-8%. For grinding medicinal substances that form poisonous or irritating dust, use the least dusty ball mills. Grinding is carried out in separate rooms, and the mills are closed with special covers. During the grinding process, personal safety measures are applied, using special clothing for personnel. Prefabricated shredder GF-300A, used in the modern pharmaceutical industry, consists of the following components: shredder, dust collector and collector for raw materials. The principle of operation is as follows: after loading into the hopper, the raw material falls between fixed and movable toothed disks, which rotate at high speed. The raw material is transformed into powder by pulsating drilling, cutting, kneading and by pushing granules of different sizes. All working parts are made of high quality stainless steel. The grinder is manufactured in accordance with GMP standard. In the CGS jet mill from the German company NETZSCH, the grinding energy is generated by gas jets through horizontally integrated air nozzles. The gas jets create a fluidized bed in which the particles are accelerated by the gas jet. As the particles move towards the center and at the very center of the chamber, they collide with other particles moving slower, and thus comminution occurs. The air appearing in the center of the chamber «transports» the particles to the classifier, which in turn sifts out the particles that are too coarse and allows only those particles that match the settings, such as the speed of the classifier and the amount of air to pass through.

With the CGS jet mill it is possible to achieve particle dispersities in the range of 2- /0 µm. The desired dispersity is set via a rotary classifier. Depending on the medical purpose and method of application, powders have different dispersity requirements. Crystalline powders intended to be dissolved before use by patients (e.g. magnesium sulphate, boric acid) are usually dispensed as medium, medium-fine or even coarse powders. Powder powders intended for the treatment of various injuries of the skin or mucous membranes should have a high degree of dispersibility in order to increase the total surface area of the particles of these substances and reduce their traumatic effects. For example, in calcium-containing toothpastes, calcium is in the form of fine needle-like crystals so that these crystals can fill cracks in the enamel of teeth. In the manufacture of powders, it is necessary to take into account the physicochemical properties of drugs and excipients. In the manufacture of complex powders take into account: the size and shape of crystals, solubility in ethanol, the ability to adsorb (including coloring ability), the ability to electrify (sulfur, butadione) and atomize (magnesium oxide), volatility (menthol, camphor, essential oils, etc.). Difficult to grind substances (camphor, menthol, iodine) are ground in the presence of volatile solvents – alcohol or ether, which are surfactants (10 drops of alcohol or 15 drops of ether per 1 g of substance). They facilitate the process of destruction, produce a cleaving effect and, adsorbed on the smallest particles, prevent aggregation, stabilize the powder mass. Substances with coloring properties are introduced avoiding their direct and prolonged contact with the grinding surfaces of the equipment. To avoid moistening of the powder mixture and to improve grinding, some substances (sodium and magnesium sulfates, alum) should be used dried, having previously dried them at a temperature of 40-50°C.