574 PRINCIPLES OF CHEMISTRY 



salts and such very characteristic spectra that the least traces of 

 them 3d are discovered with great ease by means of the spectroscope. 

 For instance, lithium gives a very brilliant red coloration to a flame 

 and a very bright red spectral line (wave-length, 670 millionths mm.), 

 which indicates the presence of this metal in admixture with compounds 

 of other alkali metals. 



Lithium, Li, is, like potassium and sodium, somewhat widely spread 

 in siliceous rocks, but only occurs in small quantities and as mere traces 

 in considerable masses of potassium and sodium salts. Only a very 

 few rather rare minerals contain more than traces of it, 39 for example, 

 spodumene and lithia mica. Many compounds of lithium are in all 

 respects closely analogous to the corresponding compounds of sodium 



58 in order to show the degree of sensitiveness of spectroscopio reactions the 

 following observation of Dr. Bence Jones may be cited: If a solution of 8 grains of 

 a lithium salt be injected under the skin of a guinea-pig, after the lapse of four 

 minutes, lithium can be discovered in the bile and liquids of the eye, and, after ten 

 minutes, in all parts of the animal. 



sy Thus spodumene contains up to 6 p.c. of lithium oxide, and petolite, and lepidolite 

 or lithia mica, about 3 p.c. of lithium oxide. This mica is met with in certain granites 

 in a somewhat considerable quantity, and is therefore most frequently employed for the 

 preparation of lithium compounds. The treatment of lepidolite is carried on on a large 

 scale, because certain salts of lithium are employed in medicine as a remedy for certain 

 diseases (stone, gouty affections), as they have the power of dissolving- the insoluble 

 uric acid which is then deposited. Lepidolite, which is unacted on by acids in its 

 natural state, decomposes under the action of strong hydrochloric acid after it has been 

 fused. After being subjected to the action of the hydrochloric acid for several hours all 

 the silica is obtained in an insoluble form, whilst the metallic oxides pass into solution 

 as chlorides. This solution is mixed with nitric acid to convert the ferrous salts into 

 ferric, and sodium carbonate is then added until the liquid be'comes neutral,- by which 

 means a precipitate is formed of the oxides of iron, alumina, magnesia, &c., as insoluble 

 oxides and carbonates. The solution (with an excess of water) then contains the chlor- 

 ides of the alkaline metals KC1, NaCl, LiCl, which do not give a precipitate With 

 sodium carbonate in a dilute solution. It is then evaporated, and a strong solution of 

 sodium carbonate added. This precipitates lithium carbonate, which, although soluble 

 in water, is much less so than sodium carbonate, and therefore the latter precipitates 

 lithium fr'om strong solutions as carbonate, 2LiCl + Na^COs = 2NaCl + Li 2 CC>3. Lithium 

 carbonate, which resembles sodium carbonate in many respects, is a substance which is 

 very slightly soluble in cold water and is only moderately soluble in boiling water. In 

 this respect lithium forms a transition between the metals of the alkalis and other 

 metals, especially those of the alkaline earths (magnesium, barium), whose carbo- 

 nates are only sparingly soluble. Oxide of lithium, Li 2 O, may be obtained by heating 

 lithium carbonate with charcoal. Lithium oxide in dissolving gives (per gram-molecule) 

 26,000 heat units ; but the combination of Li 2 with O evolves 140,000 calories that is, 

 more than Na-jO (100,000 calories) and K 2 O (97,000 calories), as shown by Beketoff (1887). 

 Oeuvrard (1892) heated lithium to redness in nitrogen, and observed the absorption of 

 N and formation of Li 5 N, like Na 3 N (see Chapter XII. Note 50). 



LiCl, LiBr, and Lil form crystallo-hydrates with H 2 O, 2H 2 O, and 8S 2 O. As a rule, 

 LiBr2H 2 O crystallises out, but Bogorodsky (1894) showed that a solution containing 

 LiBr + 8'7H 2 O, cooled to 62, separates out crystals LiBrSH 2 O, which decompose at + 4 

 with the separation of H 2 O. LiF is but slightly soluble (in 800 parts) in water (and still 

 less so in a solution of NH 4 F). 



