SODIUM LITUIUM.] 



CHEMISTRY. 



387 



bitartrate, or cream of tartar. With chromic acid, the 

 chromate and bichromate are formed, of whicli we fully 

 spoke under the head of Chromium. The acetate, oxa- 

 late, citrate, malate, prussiate, and numerous other salts, 

 are produced by the union of potash with the respective 

 acids. Were we to attempt to give a list of all the salts 

 producible by the union of potass with acids, we should 

 have to include the whole of the latter. All the combi- 

 nations of potash are soluble in water ; and hence they 

 become of great value as tests in the laboratory. The 

 carbonate is often employed as a flux, both for blow-pipe 

 investigations, and for the analysis of siliceous matters. 

 Potassium itself is largely employed as a deoxidising 

 agent, owing to its powerful attraction for oxygen. 



SODIUM. 



IN many respects sodium resembles the metal potassium. 

 It is prepared in an exactly similar manner ; the car- 

 bonate of soda, however, being used. Its specific gravity 

 nearly equals that of water ; its symbol is Na, and tl>e 

 equivalent 23. Sodium will not inflame if cast in c< Id 

 water. If, however, hot water be used, or the metal be 

 placed on a piece of wetted blotting or filtering-paper, it 

 will decompose water, and afford a yellow flame. The 

 production of this colour by salts of soda in flame, is 

 a general characteristic of their presence. 



Soda is the protoxide of sodium ; and, as an article of 

 manufacture, it is of great importance. The ordinary soda 

 of commerce is a sub-carbonate, from which the hydrate 

 may be obtained by boiling a solution of the salt with 

 lime. The earth combines with the carbonic acid, and 

 BO leaves the soda itself in its caustic state. 



Common salt is the source whence soda is manu- 

 factured. The salt is mixed with dilute sulphuric acid, 

 which so forms the sulphate ; the hydrochloric acid pass- 

 ing off in a gaseous state. The sulphate is then mixed 

 with sawdust or small coal, and roasted for some time. 

 By this the sulphur is deoxidised, and the sulphuric acid 

 decomposed. An impure carbonate of soda is produced, 

 which is purified by solution and crystallisation. Soda 

 ash, as it is termed, is the same substance in the form 

 of a powder. It, however, generally contains a 

 proportion of carbonic acid ; approaching more nearly to 

 a pure fused hydrate. 



Soda is largely employed .for numerous purposes. 

 With oils, it forms ordinary hard soap uniting with the 

 stearine of the fat, and so producing a stearate of soda. 

 The common yellow soap of commerce often contains 

 resinous matter, which is \ised for the sake of cheapness. 

 Mottled soap is produced by adding a small portion of 

 copperas (sulphate of iron), by which the veins, noticed 

 in that article, are obtained. The better kind of soapi, 

 such as curd, Arc. , are made from mutton fat ; and brown 

 Windsor, and other scented preparations, are manu- 

 factured therefrom. In bleaching, soda is used to re- 

 move grease and resinous matters from the yarn and 

 cloth ; but of late years, lime has been substituted for 

 it, as being a cheaper material. The domestic uses of soda 

 we need not refer to. 



Soda unites to form soluble salts with most of the 

 acids ; and the following are amongst the chief of its 

 salts : Sulphate of soda, formerly known as Glauber's 

 salts, is easily prepared by adding sulphuric acid to any 

 salt of soda. It is extremely soluble in water ; and may 

 be employed by the student in initiatory experiments on 

 crystallisation. If this salt be dissolved in boiling-water 

 tn saturation, and the solution be put away to cool in a 

 glass flask carefully corked up, it will not crystallise if 

 kept quite still. The instant the cork is removed or a 

 small piece of sand be dropped in, the whole liquid will 

 shoot out into beautiful crystals, and be converted into 

 a solid mass. If the external part of the vessel bo held 

 in the palm of the hand, a considerable evolution of heat 

 will be also noticed. 



Soda and sulphur unite to form sulphites and the hypo- 

 sulphite. The latter salt has been extensively employed 

 as, a " fixing' 1 a^fiit by photographers ; and is produced 

 by beating the sulphate with sulphur. It is a crystalline 



body ; and in a solution with water, readily dissolves 

 oxide of silver hence its employment in the way we have 

 named. Nitrate of soda is prepared by adding nitric acid 

 to any of the soda salts, with the exception of the sul- 

 phate. In its properties it greatly resembles nitre ;* 

 and, in fact, is sometimes employed as a substitute for 

 that material, in the manufacture of gunpowder and fire- 

 works, for which purpose it is largely imported into this 

 country from India. Its natural production is due to 

 the presence of decomposing animal matter, which affords 

 th/3 nitric acid of the salt. 



Chloride of sodium is the well-known common salt. 

 This substance abounds in nature ; and is a constituent 

 of sea and river water, in variable proportions. It is 

 obtained from various sources as the evaporation of sea- 

 water. Our supplies for domestic use are drawn from 

 the salt mines, ui which the most notable are those of 

 Cheshire, in England, and Cracow, on the continent. 

 The rock-salt has a yellow or brownish colour, owing 

 to the presence of oxide of iron. On being dissolved, 

 however, this oxide falls down in an insoluble form. 

 The liquor is then evaporated, and left to crystallise, 

 when white salt, such as is used at our tables, is afforded. 

 Pure chloride of sodium is obtained by adding hydro- 

 chloric acid to a solution of carbonate of soda. 



Common salt seems to be essential to animal ex- 

 istence ; for not only is it used as a condiment by man, 

 but it is a great favourite with almost all animals, form- 

 ing a constituent of their bodies. We may refer our 

 readers for further information on this subject, to the 

 remarks of Dr. Moleschott, at a previous page, f 



We have already described the carbonate of soda, as 

 obtained from common salt. In an impure form it ig 

 produced from the ashes of sea-plants ; and, as such, is 

 known as barilla in commerce. At one time, the only 

 source of soda was that of burning sea-weed ; and in 

 many parts of the English and .Scottish coasts, the 

 names of small villages are derived from the " pans" in 

 which the barilla, or kelp, was produced. If a stream 

 of carbonic acid be passed through a solution of the car- 

 bonate, a bicarbonate is afforded, which is largely used 

 as an antacid in medicine. A natural carbonate, con- 

 taining two equivalents of soda to three of carbonic acid, 

 is found in some places ; but not in quantities to make 

 it of much value as an article of commerce. 



Borax, which is a biborate of soda, is largely imported 

 from Tuscany, which affords a natural supply of boracic 

 :i--i'l. This salt is much used by metallurgists and 

 others, as a flux ; and with many oxides it affords a glass. 

 It is much used in the production of artificial gems. 



With acetic, oxalic, and other vegetable acids, soda 

 unites to form salts ; but as these are of no special im- 

 portance, we shall not further allude to them. 



LITHIUM. 



THIS metal, like potassium and sodium, may be obtained 

 from its oxide by means of a powerful voltaic battery ; 

 and in its general characteristics it is much like them. 

 Its equivalent is 6'5 ; the symbol, L ; and its specific 

 gravity much less than either of the alkaline metals. 

 Its oxide, lithia, is analogous to soda and potass ; and, 

 like them, possesses alkaline properties. It is a con- 

 stituent of the tourmaline and other minerals ; and forms 

 a link between the alkalies and earths. As, however, 

 it is of j,Teat rarity, we shall not occupy any space in 

 its consideration. We may observe, that Messrs. 

 Bunsen and Kirchoff have discovered, by means of their 

 spectrum analysis, a new element, which has been 

 termed cajaium, in some of the compounds of lithia. 



TERRIGENEOUS METALS, OR THOSE 

 PRODUCING EARTHS. 



HAVING described the properties of the metals proper, 

 and of those producing alkalies, we shall now turn to a 

 very interesting branch of chemical scu-iiru, and proceed 

 to describe those metals which, by oxidation, produce 



Bee ante, p. 3SI5. t Ante, p 3i4. 



