51 



temperatures ; dissolve readily in water, alcohol and ether. 

 Citric acid is distinguished from the similar tartaric acid by the 

 following tests. It evolves on heating no smell of burning 

 sugai', but a different empyreumatic odour ; it forms no scantily 

 soluble acid salt with potash, and is not turbidified by lime-water 

 in the cold, but yields with it when heated a precipitate, which 

 •disappears again on cooling. The salts of the alkalies are readily 

 :soluble in water, those of the other bases slowly or not in water. 

 The salt obtained by acetate of lead and dried at 120° is=:3 PbO + 

 Ci + HO, and contains 32 '68% acid. 



Cnicill=:C42 H2S O15. In the leaves of Carbenia benedicta, 

 ■Oentaurea Calcitrapa and other Cynarocephalous plants of 

 Compositse. Is prepared like Salicin. Crystallises in white, 

 silky needles, has a remarkably bitter taste; permaiient at the air, 

 neutral, fusible, not volatilisable without decomposition ; dissolves 

 sparingly in cold, much better in boiling water, readily in alcohol, 

 wood-spirit, scarcely in ether, not in oil of turpentine and in fixed 

 oils, in concentrated sulphuric acid with beautiful red colour, 

 turning black when heated. 



Cocain =::C32 Hi9 NOg. In the leaves of Erythroxylon Coca. 

 Exhaust with water of 60° to 80°, precipitate the liquid with 

 acetate of lead, precipitate the filtered solution with a saturated 

 solution of sulphate of soda, filter, concenti-ate, render slightly 

 alkaline by means of carbonate of soda, and shake repeatedly with 

 ether. Distil ofi" the bulk of the ether from the ethereous solu- 

 tions, leave the rest of the solvent to evaporate in the cold, 

 and withdraw a part of the pigment from the remaining impure 

 C. by distributing it in cold water. Now pour a thin layer of the 

 impure chloride of C. into Graham's dialysator made of 

 parchment-papei-, and leave to diffuse in three changes of water 

 for three days, whereby most of the chloride of C. will be 

 diffused into the water, while much of the pigment remains in the 

 dialysator. Throw down the C. in the solution with carbonate of 

 soda, dissolve in alcohol, add of acetic acid enough to render it 

 acid, and allow to evaporate spontaneously over sulphuric acid. 

 The C. remains free of acetic acid, and is withdrawn from the 

 remnant by ether, while the foreign matters are left undissolved 

 and combined with acetic acid under the form of oily drops. — It 

 crystallises in large, colourless klinorhombic prisms of at first 

 somewhat bitter, afterwards cooling taste; of alkaline reaction, 

 fuses at 98°, may be sublimated for a small part with careful 

 heating, dissolves in 704 parts cold and a little more copiously in 

 hot water, readily in alcohol, and better still in ether; readily in 

 diluted acids, in concentrated sulphuric acid without colour, but is 

 carbonised by heat; separates when heated with concentrated 

 hydrochloric acid into benzoic acid and a new crystalline base of 



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