Moh’s scale

Hardness. There are several hardness (qv) scales. In selecting size reduction equipment generally hardness is expressed according to the Mohs s scale, where a body in one range scratches a body in the immediately previous range ... 

Hardness It is not possible to obtain a reliable figure for the hardness of anodic coatings with either the indentation or scratch methods, because of the influence of the relatively soft metal beneath the anodic film, and the presence of a soft outer layer on thick films. On Moh s Scale, the hardness of normal anodic films lies between 7 and 8, i.e. between quartz and topaz. 

The hardness of an enamel surface is an important property for such items as enamelled sink units, domestic appliances, washing machine tubs which have to withstand the abrasive action of buttons, etc. On Moh s scale most enamels have a hardness of up to 6 (orthoclase). There are two types of hardness of importance to users of enamel, viz. surface and subsurface. The former is more important for domestic uses when one considers the scratching action of cutlery, pans, etc. whereas subsurface hardness is the prime factor in prolonging the life of enamelled scoops, buckets, etc. in such applications as elevators or conveyors of coal and other minerals. 

Table 10.13. Selection of comminution equipment for various materials (after Marshall, 1974) Note Moh s scale of hardness is given in Table 10.12... 

Moh s scale Hardness scale ranging from 1 for talc to 10 for diamond. 

Boron Carbide, B4C coml prod called, tNor-bide, mp ca 2375°, d 2.52 is prepd by heating anhyd boric oxide B30, with carbon in graphite resistance furnace at ca 2500°. Its special interest is due to its remade able hardness jwhich lies on the Moh s scale betw thatjof silicon carbide and diamond. Used as an abrasive. Detailed description of this compd is given in Kirk Othmer 2(1948), 830-4(21 refs)... 

Hardness.—This is greater than that of white phosphorus, being 3-5 on Moh s scale. 

Enthalpy of fusion Enthalpy of vaporization Specific heat at 200 K Hardness (Moh s scale)... 

Abrasiveness This is measured on Moh s scale 1 — 3 = soft substances, 8 — 10 = hard substances. 

On the Moh.s scale diamond is 10 and quartz 7. An alternative measure is the Knoop hardness measured with a 100-g load typical values on this scale are diamond 7000, boron carbide 2750, corundum 2100, topaz 1340, quartz 820, hardened tool steel 740. 

Aluminum nitride EINECS 246-140-8. Used as a semiconductor in electronics, nitriding of steel steel manufacture. Crystals mp 2150-2200° hardness 9 to 10 on Moh s scale. Atomergic Chemetals Carborundum Corp. Mandoval Ltd Sigma-Aldrich Fine Chem. 

Tin is a relatively scarce element with an average abundance in the Earth s crust of about two parts per million (ppm) compared with 94 ppm for zinc, 63 ppm for copper, and 12 ppm for lead. Tin is produced from lode (hard-rock) deposits and placer deposits derived from the lodes. The tin mineral cassiterite (Sn02) is the source of most tin production. A notable exception is the complex tin sulfide minerals in the subvolcanic or tin-silver lode deposits in Bolivia. Cassiterite has a high specific gravity (6.8 to 7.1), a Moh s scale hardness of 6 to 7, and is usually a dark brown or black color with an adamantine luster. 

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