OR′CIN. C7H8O2. The general product of the decomposition of the acids obtained from the tinctorial lichens under the influence of heat or the alkaline earths.
Prep. 1. The powdered lichen is treated with boiling alcohol, the tincture filtered whilst hot, and again after it has become cold; the alcohol is then removed by distillation, and the remainder evaporated to the consistence of a syrup; this is redissolved in water, and the solution is again filtered and evaporated to a syrup; it is then set aside some days in a cool place, and the crystals of orcin which form are collected, and dried by pressure in bibulous paper. Impure.
2. Lecanoric or orsenillic acid (impure will do) is boiled in baryta water, and the excess of baryta is precipitated by carbonic acid; the filtered liquid is then evaporated to a small bulk, and set aside to crystallise, as before.
Prop., &c. Large, square, prismatic crystals; slightly yellowish; intensely sweet; very soluble in both water and alcohol; melt to a syrupy liquid, and then distil unchanged. Alkalies decompose it; when exposed to the air, it gradually reddens. (See above.)
OREIDE. A variety of brass, in appearance very much like gold. The following, according to MM. Menrier and Valient, its inventors, is the composition of this alloy:—Copper, 100 parts; zinc, 17 parts; magnesia, 6 parts; sal ammoniac, 3·6 parts; quicksilver, 1·80 parts; tartar of commerce, 9 parts. The copper being first melted, the other ingredients are added by small portions at a time, the whole being kept in fusion for about half an hour, and during which time they are kept skimmed. The oreide has a fine grain, is malleable, is capable of being brilliantly polished, and has its lustre restored by the use of acidulated water.
OR′ELLIN. A yellow colouring matter contained together with bixin in annotta. It is soluble in water and in alcohol, slightly soluble in ether, and dyes alumed goods yellow. Also the name sometimes given to purified annotta. The commercial annotta is dissolved in an alkaline solution, either caustic or carbonated, and then precipitated by an acid. See Annotta.
ORES. The mineral bodies from which metals are obtained. The processes adopted for this purpose constitute OPERATIVE METALLURGY; those by which their value is determined, MINERAL ASSAYING.
A very small proportion only of the metals are met with in nature in the free or elementary
condition, by far the greater number found being united with some non-metallic element or elements, in definite atomic proportions, and as such forming true chemical compounds, in which in almost every instance the physical and chemical properties of the metal are obliterated. In these bodies, which, when they are used as sources of the metals commonly employed by man, are called ORES, the metal is mostly combined with oxygen or sulphur, sometimes with carbonic acid, and less frequently with chlorine, and other negative elements. Thus we have the native combinations of iron and oxygen constituting the minerals known as hæmatite iron ore (Fe2O3), bog iron ore (Fe2O3,3H2O), and magnetic iron ore (Fe2O3,FeO), of tin and oxygen in tin stone (SnO2), and of copper and oxygen known as red copper ore (Cu2O). Of the principal ores into which sulphur enters as a chemical ingredient, we may mention native sulphide of antimony (Sb2S3); the two native sulphides of arsenic, realgar (As2S2) and orpiment (As2S3); galena, or native sulphide of lead (PbS), blende, or native sulphide of zinc (ZnS), and cinnabar, or native sulphide of mercury (HgS). Besides the above, there are also certain double native sulphides, such as the double sulphide of iron and copper, known as Peacock ore, and having the composition Fe2S3,3Cu2S; iron and copper pyrites (Fe2S3,Cu2S); and red silver ore (Sb2S3,3AgS).
In the state of carbonate, ores occur—as malachite native carbonate of copper (CuCO3.Cu(HO)2), as calamine, or native carbonate of zinc (ZnCO3), and as spathose iron ore, or native carbonate of iron (FeCO3). Horn silver and horn lead, the former having the composition AgCl, and the latter PbCO3 + PbCl2 are illustrations of ores containing chlorine.