301 



LITHOFELLIC ACID. 



LITHOGRAPHY. 



302 



derived from Aifloj, a stone, it having been found in the mineral 

 kingdom only. 



The principal sources of lithium are the minerals lepidollle, triphane, 

 and petalite. Arable of their per-centage composition is given under 

 the respective names in the NAT. HIST. Div. Their formulae is thus 

 represented in Miller's ' Elements of Chemistry : ' 



Lepidolite or lithia mica 

 Triphane or spodumene 

 FeUlite . 



2[(LK) F1] + 4(A1 4 3 , 3 SiOJ 

 3t(L.\a)0, SiO,] + 4(Al 2 O 3 , 3Si0 2 ) 

 3[(L.Na)0, 2SiO 2 ] + 4(Al. ! 3 , 6SiO 3 ) 



Lithium may be obtained in the metallic state by decomposing its 

 chloride with an electric current generated from five or six pairs of 

 Bunsen's nitric acid battery. It is a white metal, harder than potassium 

 or sodium, but softer than lead. It melts at 356 Fahr., and is not 

 volatile when heated to redness. At common temperatures two pieces 

 may be welded together by pressure. It can be drawn into wire, but 

 is less tenacious than lead. Its specific gravity is 0'5936, nence it is 

 the lightest solid body known ; it floats even on the surface of naphtha. 

 It rapidly oxidises in the air, and if assisted by heat burns with a 

 brilliant carmine-tinted name. It decomposes water in a similar manner 

 to sodium, and ignites when placed in strong nitric acid. 



The equivalent of lithium is 6'53. 



Ltt/tiam and oxyyen form but one compound, namely : 



Oxide of lithium (LO). The mineral from which it is to be extracted 

 is reduced to an almost impalpable powder, and then ignited with 

 twice its weight of quicklime in a silver crucible. The resulting mass 

 is next treated with hydrochloric acid, then with sulphuric acid, and 

 the sulphate of lithia thus formed dissolved out from sulphate of lime 

 by washing with water ; a small quantity of oxalate of ammonia is now 

 add-.d to remove lime that may have been dissolved, and sulphuric acid 

 thrown out of solution by the addition of baryta water. On evaporating 

 the filtered liquid the lithia separates out in grains. If necessary, it 

 may be fused in a. silver crucible, vessels of platinum being rapidly 

 corroded by it. 



Hydrate of lithia is not so soluble in water as the hydrates of potash 

 or soda are. It has a strong caustic taste, and tums vegetable reds to 

 blues. In the fused state it is white, transparent, has a crystalline 

 structure, does not deliquesce in the air, and dissolves in water with 

 disengagement of heat. 



Lithium and chlorine form : 



Chloride of lithium (LCI). It is readily made by dissolving the oxide 

 in hydrochloric acid. On evaporation the solution yields cubical 

 crystals, very soluble, exceedingly deliquescent, and containing four 

 equivalents of water of crystallisation. 



Jn'/.ide of lithium (LI + 6HO) crystallises in needles, and fluoride of 

 lithium in small opaque grains. 



Sulphide of lithium is formed in the same way as sulphide of sodium, 

 and much resembles that compound. 



Sulphate of luhia (LO,S0 3 + Aq). On evaporating the solution of 

 this salt, obtained as described under oxide of lithium, tabular crystals 

 of the above composition are obtained. 



Carbonate of lithia (LO,CO g ) is precipitated when carbonate of am- 

 monia is added to a strong solution of chloride of lithium. It may be 

 washed with alcohol, in which it is insoluble. It is slightly soluble in 

 water, the resulting solution having an alkaline reaction. On the 

 application of heat to the dried salt it fuses, and solidifies on cooling 

 to a white transparent mass of pearly lustre and crystalline fracture. 



Carbonate of lithia has been recommended to be administered as a 

 solvent for calculi in the bladder. It certainly effects the solution of 

 uric acid most rapidly when triturated with that substance in a mortar 

 containing a little water ; but as many calculi do not contain uric acid, 

 and as most of those that do contain it have an external coating of 

 phosphates, it f . >llows that the carbonate of lithia, being an alkaline 

 substance, may do more harm than good if administered indiscriminate ly. 



DoiMe phj#p/uae of lithia and soda. When phosphate of soda is 

 added to a solution of a lithium salt no precipitate is at first produced ; 

 but on evaporating to dryness the above compound remains as a white 

 powder, almost insoluble in water, and quite insoluble in dilute aqueous 

 solutions of the alkaline phosphates. Before the blowpipe, with 

 carbonate of soda, the double salt fuses to a clear bead, transparent 

 when hot but opaque when cold. A fused specimen examined by 

 Bcrzelius contained NaO,LO,P0 5 , but generally its composition is very 

 variable, probably on account of the two bases, lithia and soda, being 

 capable of replacing each other. 



Teit* for lithium. Salts of lithium are readily fusible in the blowpipe 

 flame, imparting to it a carmine red colour, and attacking the platinum 

 wire holder or other platinum vessel in a characteristic corrosive 

 manner. Their presence is further confirmed by forming the carbonate 

 and double phosphate in the way already mentioned. 



LITHUFKLLIC ACID. (C, H M O 8 ). Lithvfellinic acid. The once 

 celebrated bezwr-stont* intestinal calculi of certain animals almost 

 wholly consist of this acid. To isolate it, the stones [BEZOARS], are 

 reduced to powder and boiled in alcohol, the dark solution decolorised 

 with animal charcoal and evaporated, when the lithofellic acid crystal- 

 i*e out in small, colourless, transparent six-sided prisms. It may 

 U be decolorised by precipitating its alkaline solution with hydro- 

 chloric acid, washing, drying, and crystallising from alcohol. 



Lithofellic acid is insoluble in water, slightly BO in ether, and very 

 soluble in alcohol. Heated to 401 Fahr. it melts, and at a little higher 

 temperature is converted into a resin, the fusing point of which is only 

 230 Fahr. In this particular, and in the fact that it is readily soluble 

 in solutions of the alkalies and their carbonates and in acetic acid, 

 lithofellic acid is easily distinguished from cholesterin, a body that 

 otherwise it much resembles. 



Submitted to dry distillation, it yields an oily acid, termed pyrolitho- 

 feme acid (C^H^Oa). 



Lithofellic acid combines with bases to forrn lithofeHates, a class of 

 compounds that have not been much studied. The silver salt appears 

 to contain C, H 35 Ag O g . 



LITHOGRAPHY, the art by which impressions or prints are 

 obtained by a chemical process from designs made with a greasy mate- 

 rial upon stone. It has therefore been properly termed chemical 

 printing, to distinguish it from all other modes of obtaining impres- 

 sions, which are mechanical. In printing from an engraving on a 

 copper or steel plate, the ink is delivered from the incisions made 

 therein with the graver or etching-needle. An engraving on wood, on 

 the contrary, gives its results from the projecting surface of the block, 

 or those parts which are not cut away by the graver. The lithographic 

 process differs from both these modes, the impressions being obtained 

 (by strict attention to chemical affinity) from a level surface. The art 

 of lithography was first practised by the inventor Alois Senefelder, in 

 1798, the peculiar property on which it depends having being dis- 

 covered by him a few years earlier. [SENEFELDER, ALOIS, in Biou. 

 Div.] 



There are various styles of lithography, as will presently be seen ; 

 but the principle of the art is uniformly the same, being, as we have 

 said, based upon that of chemical affinity. 



The stone best calculated for lithographic purposes is a sort of cal- 

 careous slate, found in large quantities on the banks of the Danube in 

 Bavaria, the finest being that found at Solenhofen, near Munich. 

 Stones much resembling the German have been found in some parts of 

 Devonshire and Somersetshire, and also in Ireland ; but the stones 

 found in this kingdom have been proved to want some of the essential 

 qualities of those brought from Germany, which are therefore, at 

 least for artistic works, exclusively used. Even the Bavarian stones 

 vary much in quality, all the strata not being equally good : some are 

 too soft, and others are rendered unfit for use by the presence of chalk, 

 flaws and veins, and fossil remains. A good stone is porous yet brittle, 

 of a pale yellowish-drab, and sometimes of a gray neutral tint. The 

 stones are split or sawn into slabs varying from 1 4 to 3 inches in thick- 

 ness, which are then cut or squared into the different sizes necessary 

 for use, and the face or upper surface of each is made level. In this 

 state are the stones sent from the quarry ; but further preparation is 

 yet necessary to fit them for the immediate use of the artist, and 

 they are either grained or polished, according to the nature of the work 

 they are intended to receive. The mode of preparing a grained stone, 

 as it is called, is this : A stone, being laid flat on a table, has its sur- 

 face wetted, and some sand sifted over it through a very fine wire- 

 sieve. Another stone is laid with its face downwards upon this, and 

 the two are rubbed together with a circular motion, to produce the 

 requisite granulation, which is made finer or coarser, to suit the taste 

 or intention of the artist. The stones thus prepared are used for 

 drawings in the chalk manner, or for imitations of those produced 

 with the black-lead pencil. Great care is requisite in this mode of 

 preparation, to keep the granulation uniform and the surface free from 

 scratches, the presence of which would otherwise much disfigure the 

 future work. Writings, imitations of coloured drawings, etchings, pen 

 and ink sketches, &c., require the face of the stone to be polished, 

 which is effected by rubbing it with pumice-stone and water,.or pumice 

 stone dust and water applied with rags. 



The two principal agents used for making designs, writings, &c., on 

 stone, are called lithographic chalk and lithographic ink. They are 

 composed of tallow, virgin-wax, hard tallow soap, shell-lac, sometimes 

 a little mastic or copal, and enough lampblack to impart a colour to 

 the mass. These are incorporated by a peculiar process of burning in 

 a closely-covered saucepan over a fire, and the whole is ultimately cast 

 into a mould, and receives the form calculated to fit it for use. The 

 ingredients are the same in the chalk and the ink, but the proportions 

 are varied, and a little Venice turpentine is often added in the latter. 

 The chalk is used as it comes from the mould in a dry state, 

 but the ink is dissolved by rubbing, like Indian ink, in water, and 

 is used in a pen or camel-hair pencil. It will be perceived that it 

 is the presence of the soap in this greasy material which renders it 

 soluble in water. 



To render the lithographic process intelligible, let it be supposed 

 that the artist now completes a drawing with the chalk just described, 

 upon a grained stone, much as he would make a drawing in pencil or 

 chalk upon paper. If, while in this state, a sponge filled with water 

 were passed over the face of the stone, the drawing would wash out, 

 the chalk with which it is made being, as we have seen, soluble in 

 water, by reason of the soap which it contains. Before therefore it is 

 capable of yielding impressions, a weak solution of nitrous acifl is 

 poured over it, which unites with and neutralises the alkali or soap 

 contained in the chalk, and renders it insoluble in water. After this 

 the usual course is. to float a solution of gum over the whole face of the 



