affinity

[In Ger. affinität; Fr. off in ité; Ital. affinità, fr. Lat. aff in it as (1) neighbourhood, (2) relationship by marriage, (3) union, connection.] I. Ordinary Language & Law: 1. Lit. The relationship contracted by marriage between a husband and his wife's kindred, or between a wife and her husband's kindred. It is opposed to consanguinity, or natural relationship by blood. It is of three kinds: (1) direct , viz., that subsisting between a husband and his wife's blood relations, and vice vers a; (2) secondary , or that which subsists between a husband and his wife's relations by marriage; and (3) collateral , or that which subsists between a husband and the relations of his wife's relations. The word affinity in this, as other meanings, may be followed by with , to, or between . "And Solomon made affinity with Pharaoh king of Egypt, and took Pharaoh's daughter, and brought her into the city of David."-1 Kings iii. 1. The Moor replies, That he you hurt is of great fame in Cyprus." And great affinity ." - Shakesp.: Othello , iii. 1. "He would doubtle gladly have avoided the scandal which must be the effect of a mortal quarrel between persons bound together by the closest ties of consanguinity and affinity ."-Macaulay: Hist. Eng., ch. vii. 2. Connections (not nece arily by 1.); a ociates. 3. Fig .: The resemblance produced, more or le remotely, by a common origin between languages now in many respects distinct. Or generally, the similarity between things which e entially resemble each other. "There is a close affinity between imposture and credulity."-Lewis: Influence of Authority, ch. iii. II. Biol . Sing . & plur .: A resemblance, or resemblances, on e ential points of structure between species, genera, orders, cla es, ., really akin to each other, and which should be placed side by side in any natural system of cla ification. To this Mr. Darwin would add that the resemblances arise from the fact that the species in which they occur were derived at a more or le remote date from a common ancestor. Affinity differs from analogy , the latter term being applied to resemblances between animals or plants not really akin, but which ought to be more or le widely separated in cla ifications. Thus the falcons, the hawks, the eagles, ., are related to each other by genuine affinity; but the similarity on certain points, such as the po e ion of retractile claws, between the raptorial birds and the feline race of mammals, is one only of analogy. "We can understand, on these views, the very important distinction between real affinities and analogical or adaptive resemblances."- Darwin : Origin of Species, ch. xiii. the nature of the afinities which connect together whole groups of organisms."- Ibid., pt. i., ch. i. III. Chemistry: 1. Chemical affinity, or chemical attraction, is the force by which union takes place between two or more elements to form a chemical compound. According to another definition, it is a force exerted between two or raore bodies at an infinitely minute distance apart, by which they give rise to a new substance having different properties to those of its component parts. Elements have the greatest affinity for other elements which differ most in their chemical properties. Thus H has great affinity for Cl and O, but the affinity between O and Cl is much weaker. Acids unite readily with alkalies, most metals with sulphur. When two salts are mixed together they are decomposed if an insoluble substance can be formed: thus AgNO3 + NaCl yields NaNO3 and insoluble AgCl, and BaCl + MgSO4 yields MgCl, and insoluble BaSO4 A strong acid generally expels a weaker one, as H2SO4 expels HCl or CO2, and CO2 precipitates SiO2; but when two salts are fused, if a more volatile compound is formed, it is driven off, as when NH4Cl is heated with dry CaCO3, then (NH4)2CO3 volatises. SiO2 fused with salts expels the strongest acids and forms silicates. Iron filings heated to redne in a tube decomposes the vapour of water, but Ha pa ed over red-hot oxide of iron reduces it to a metallic state. These reactions are due to the diffusion of gases, the resulting gas being diffused through the ma of vapour pa ing through the tube. The relative affinities between different substances varies with their temperature, insolubility, and power of vaporisation. The nascent state is favourable to chemical combination: thus H and N unite readily when organic matter containing Nis decomposed by heat or putrefaction, also H with S. This is due to the bonds of the atoms being liberated at the moment of decomposition. Disposing affinity is the action of a third body, which brings about the union of two other bodies, as Ag + SiO2 and alkali forms a silicate of silver; Pt is attacked by fused KHO. Organic decompositions in the presence of caustic alkali, or lime, are also examples. Catalysis is the action of a body to bring about a chemical reaction whilst the body itself undergoes no perceptible change, as MnO2 in the preparation of O from KClO3. Certain chemical compounds at high temperatures are di ociated from each other, as NH4Cl at high temperatures forms NH3 + HCL. Chemical union is promoted by finely dividing the substances; thus finely-divided metals, as iron or lead, take fire in the air, uniting with O. Alteration of temperature alters the affinity; thus mercury heated to its boiling-point absorbs oxygen, which it liberates at a higher temperature; also BaO absorbs O at a low heat, forming BaO2, and gives it off at higher temperatures. Strong bases generally replace weaker bases; thus alkalies precipitate oxides of iron, . "The affinity which held together the elements of the organic substances is destroyed by the cause which occasioned their death, and they are set free to obey new affinities and form new compounds."- Todd Bowman: Physiol. Anat., i. 12. 2. Affinity of solution is such an affinity as exists between a soluble salt and the fluid in which it is di olved. Till the liquid is saturated with the salt the two can combine in an indefinite ratio, instead of being limited to the fixed proportions in which alone chemical affinity operates. IV. Nat . Phil . Current afinity: The force of voltaic electricity. V. Psychol.: An alleged attraction existing between persons, generally of the opposite sex; a supposed union or attraction of minds. Also the person exerting such influence. (A doctrine of spiritualism.) * af-fire', adv. [AFIRE.]