O.SMIL'M, KTi:.J 



CHEMISTRY. 



385 



OSMIUM, PALLADIUM, IRIDIUM, RHODIUM, 

 AND RUTHENIUM. 



THESE metals are found associated with platina. Osmium 

 has a specif! gravity of about 10 : its equivalent is 99'6 ; 

 and the symuol, Os. It somewhat resembles platiua in 

 appearance ; with oxygen, it forms several compounds, 

 amongst which is the osrnic acid. This forms salts with 

 bases, termed osmiates. 



Palladium symbol, Pd ; equivalent, 53 - 3 ; specific 

 gravity, ITS also resembles platina, but is soluble in 

 nitric acid. Ita other combinations are extremely 

 analogous to those of platina. Its chief uses have been 

 for purposes in which a freedom from ready oxidation 

 is required ; and it has lately been largely employed as 

 a substitute for gold in fixing teeth, and in making arti- 

 ficial palates. 



Iridium much resembles, in every respect, the 

 metal platina. It combines with oxygen, chlorine. 

 Its chief use has been to form the points of steel pens, 

 Ac., for which purpose its extreme hardness renders it 

 valuable. Rhodium aud ruthenium much resemble 

 platina in their properties. Rhodium has had a 

 i:ir application to that we have named in respect 

 to iridium. 



VANADIUM, TUX< fSTEX, . Mi >LYBDENUM, 

 URANIUM, ETC. 



THESE metals are all so rare as to scarcely ever come 

 under the observation of the chemist. Vanadium is 

 found in combination with iron and lead, from which 

 it is separated as vanadic acid. It combiner, in various 

 proportions, with oxygen, forming oxides; and with 

 chlorine, two chlorides are producible. 



Tungsten is obtained from a mineral called wolfram, 

 and with oxygen produces' a binoxide, and an a-id otOal 

 tungstic acid. A combination of this witli soda, the 

 tungstateof soda, has lately been highly nooOHDHMMd as 

 a material by means of which ladies cotton and other 

 dresses may be rendered non-intl.immaUe. Wo -fear 

 that its use in this respect is extremely limited, how- 

 ever valuable its properties may be. 



Molybdenum is a white metal, forming oxides and in,- 

 molybdic acid. This produce! salts with bases. 

 metal is obt lined from the native sulphide a somewhat 

 rare mineral. 



Uranium obtained from a mineral called pitch- 

 blende. It ; ,nns oxides, the chief use'of which is that of 

 colouring glass The substance so formed hag peculiar 

 optical properties in reference to epipolic dispersion of 

 light. 



Titanium is obtained from a mineral called rutile. 

 It combines with oxygen, producing oxides and the 

 titanic acid. In some of its combinations it resembles 

 the earth silica. 



Tellurium may be termed a quasi metal. It resembles 

 silver in colour, and with oxygen forms the, telluric 

 arid. Kouie analogy exists betwixt this element and 

 selenium. 



Our readers will find, in our list of the elements, many 

 other substances belonging to the family of metals proper. 

 Their properties are, however, so uncertain, and their 

 interest so slight, as not to require any detailed notice. 

 The two most interesting metallic elements lately dis- 

 covered by means of the spectrum analysis of Messrs. Bun- 

 sen and Kirchoflf, have been named curium ami rubidium ; 

 but the quantities of these yet produced are so small as 

 not to wan. -it any dependence on the characteristics 

 they present. 



KALH1KXEOUS METALS, OR THOSE PRO- 

 DUCING ALKALIES. POTASSIUM. 



FROM the barren waste of information presented by our 

 limited knowledge of many of the elements we have just 

 referred to, we turn with pleasure to the description of 

 the alkaline metals, in which every interest of a scientific 



and social nature is involved. There are few substances 

 more completely identified with our daily life, manufac- 

 tures, domestic matters, &c., than the alkalies, potass 

 and soda. All our cleansing, bleaching, and numerous 

 other processes depend on their use. The production of 

 soaps, caudles, the purification of oils, the constitution 

 of common salt, and many other products, are identified 

 with them. And we therefore feel it necessary to 

 give an extended notice both of their elements and their 

 numerous combinations. 



Perhaps no discovery ever made in chemical science, 

 gave rise to such general excitement as that by which 

 Sir Humphry Davy demonstrated that potash and soda 

 contained metals as a constituent. We learn that all 

 ranks crowded daily in the laboratory of the Royal Insti- 

 tution, to witness the new productions. Indeed, by 

 means of these metals, our knowledge of the constitution 

 of numerous other bodies has U-en largely extended. 

 Eaeh earth was ! y examined ; and as potassium 



and sodium hax an aJlinity for oxygen, it is a 



matter of no surprise that tliis affinity was employed us a 

 means of analysis, and that, too, with successful results. 

 Perhaps the most surprising practical application of the 

 discovery, has been that of an abundant production of a 

 valuable and useful metal, in large quantities, from 

 common clay, or other compounds of alumina. Chemistry 

 is ever affording us surprising and unlooked-for results; 

 aud chemists, whilst constantly hoping for new disco- 

 veries, do not forget their duty to mankind at large, in 

 applying for the benefit of mankind, in a useful form, 

 that which, seen by the light of scientific research, is 

 regarded by them with philosophical interest oidy. With 

 these prefatory remarks, we shall now proceed to describe 

 the character of the alkaline metals, commencing with 

 potassium and its compounds. 



POTASS 1 1 M, as its name would imply, is obtained from 

 potass. If a piece of fused potass be placed on some 

 phitina foil connected with a powerful voltaic battery, 

 whilst a platina wire is brought into contact with the 

 alkali, considerable effervescence will take place. Bright 

 sparks will fly off ; and if a little mercury be placed also 

 in contact with the jx>tass, it will form an amalgam with 

 the potassium thus produced. The amalgam, if dropped 

 i.iter, will decompose the liquid, owing to the asso- 

 ciated potassium combining with the oxygen, and setting 

 the hydrogen free. 



By this mode of producing potassium, the voltaio 

 it is employed to separate the oxygen from the 

 metal ; the oxide of potassium is thus decomposed, and 

 tM obtained in minute quantities. 



Potassium, however, is readily procured in any quan- 

 tity by means of the following process. The oxide of 

 potassium, or potass, is first fused, and then allowed to 

 run over iron-turnings heated to whiteness. These seize 

 the oxygen of the potass, and the metal potassium is 

 thus set free. The following engraving illustrates an 

 Fig. 70. 



arrangement by moans of which potassium can be manu- 

 factured on the small scale. In the centre is a furnace, 



3 D 



