Fine powder, definition

The micas, as a class, are difficult to grind to a fine powder one exception is disintegrated schist, in which the mica occurs in minute flakes. For diy grinmng, hammer mills equipped with an air-transport system are generally used. Maintenance is often high. It has been established that the method of milling has a definite effect on the par-... 

The definitions coarsely chopped to finely powdered , which formerly in the pharmacopoeias were given as mesh sizes, are mostly nowadays indicated without such a requirement in the DAB 10, V. 4.N6, only coarsely chopped (4000 to 2800 sieve), finely chopped (2000 sieve), and powdered (710 to 180 sieve) are distinguished. The wide particle-size ranges have rightly been criticized [1, 2], partly on the basis of extensive investigations. 

The reduction of metal hydroxides or oxides powder by polyol was first reported by Figlarz and co-workers, which gave rise to fine powders of Cu, Ni, Co and some noble metals with micrometer sizes (polyol process) [32,33]. The polyol process was first modified for the preparation of PVP-protected bimetallic and monometallic nanoclusters such as Pt/Cu, Pd/Pd, Pt/Co, Pt, Pd, etc. [34-38]. The previous results definitely revealed that Pt, Pd, Cu and Co in these PVP-protected metal or alloy nanoclusters were in a zero-valent metallic state. 

If an analyte is definitely insoluble or only soluble in solvents that are not acceptable for the standard MALDI sample preparation technique, it can alternatively be ground together with the solid matrix, preferably in a vibrating ball mill. The resulting fine powder is then spread onto the target. To avoid contamination, nonadherent material should be gently blown away from the target before insertion into the ion source. [103,108,109]... 

Pyrotechnics are invariably intimate mixtures of finely powdered fuels and oxidizers together with other additives in order to impart special effects depending on the requirement. Pyrotechnic formulations burn very rapidly when ignited as a loose powder. However, there are some applications where controlled steady burning is required for a definite time and this is achieved by compressing the mixture into columns surrounded by a relatively non-combustible material so that combustion proceeds from one end to other, layer by layer for a long duration. 

Amorphous Selenium.—(1) Vitreous Selenium.—When molten selenium is cooled in not too protracted a manner, no definite solidification or crystallisation ensues, but the mass gradually hardens and the product really represents a strongly undercooled liquid like glass. Vitreous selenium is a brittle reddish-brown substance, exhibiting a conchoidal fracture. When finely powdered and viewed in thin layers it has a deep red colour. This form has an average density of 4-28 5 the value varies slightly, possibly owing to the presence of other allotropic modifications of the element. 

Originally, only fine powders used for coloring various media were defined as pigments. This definition has been expanded to include many powdery materials, e.g., metallic powders and powders having magnetic or anticorrosive properties, which are intentionally dispersed (not dissolved) into media to increase value and/or impart some special properties,... 

When, in the case of low-density polyethylene, a vinyl chloride/ polyethylene ratio near 1 is used, the system is close to saturation and a few per cent of a fine powder containing principally PVC may form. This is avoided when a vinyl chloride/polyethylene ratio of 0.6 is used, with injection of the rest of the vinyl chloride during the polymerization. This way, the system is always definitely below saturation. Moreover, this technique improves the grafting efficiency (defined by the ratio grafted VCx 100/total polymerized VC), which increases with a decreasing vinyl chloride/polyethylene ratio during polymerization. 

These colours, termed also bronze pigments, generally consist of finely powdered metals or metallic alloys, sometimes partially oxidised or sulphided to obtain definite colours. The principal metals used for this pur-A.c, 11, 26... 

A powder is easily recognized as a mass of small dry particles, but the precise definition is inevitably somewhat arbitrary. The term fine powder is also used in an... 

It is often difficult to predict the color of the gum arabic solutions on the basis of the color of the dry tears or powder. The size and condition of the lumps and powder affect judgment considerably. The smaller the size and the more frosted, the lighter will their color appear. A dark gum when finely powdered loses its color. When the gum is finely powdered or its surface is crazed, it presents so many minute facets at all angles that practically all the light is reflected and scattered before it has traversed more than the outermost layers of the substance. Proper comparison of color should be made in solutions of a definite concentration. According to Hamy (7), the rotatory power of solutions of gum from Accu ia verek is negative, that from other species of acacia is positive. 

Classification Inorganic color Definition Finely powdered metal consisting chiefly of copper or copper-zinc alloys with small amts, of aluminum or tin Toxicology TSCA listed Uses Colorant in cosmetics, external pharmaceuticals... 

Perhaps the best place to start the discussion of cement standards is with a definition. Natural cement is currently defined in ASTM C 219 as a hydraulic cement produced by calcining a naturally occurring argillaceous [clayey] limestone at a temperature below the sintering point and then grinding to a fine powder [1]. 

Since the foregoing tests were carried out at -identical conditions of compn and temp, and in a standard test fixture, the burning times serve as a means of checking the relative fineness of thea powdered tungsten fuels. The rapid burning times indicate that both M-10 and M-20 are very fine. Also, the M-10 is definitely finer than M-20, as shown by the difference in burning times... 

---