PRODUCTS OF THE DISTILLATION OF COAL. 9 



Naphtaline is in transparent and colourless plates, has a 

 strong peculiar and not unpleasant odour, a burning aromatic 

 taste, is denser than water, insoluble in it, melts at 176, boils at 

 422.6 (217 centig.), and condenses in shining leaflets. The 

 density of its vapour is 4528 by experiment, and 4488 by calcu- 

 lation j its combining measure is 4 volumes. Naphtaline burns, 

 when heated, with a white smoky flame. It is very soluble in 

 alcohol and ether, and crystallizes from these solutions on dilu- 

 tion with water. Naphtaline is peculiarly the product of a high 

 temperature, and is furnished by alcohol and organic matters in 

 general when heated to redness. 



Naphtaline dissolves in concentrated sulphuric acid, upon the 

 application of heat ; with anhydrous sulphuric acid it combines 

 when heated, and forms a fine purple red liquid. The com- 

 pound contains three peculiar acids, which on diluting the mass 

 with water and neutralising it with carbonate of barytes, are 

 obtained in three different barytes salts, which may be separated 

 and distinguished from each other by their unequal solubility 

 and different crystallization. They are : 



Naphtalin-hyposulphuric acid or sulphonaphtalic acid, HO 

 + C 20 H 8 S 2 O 5 . It is soluble in water and crystallizes, is sour 

 and bitter, with a metallic after- taste. The hyposulphuric acid 

 it contains is not neutralised by the naphtaline, and combines 

 with the usual proportion of base to form a neutral salt. Sul- 

 phonaphtalate of barytes BaO + C 20 H 8 ,S 2 O 5 , crystallizes in 

 brilliant light spangles, burns in the flame of a candle, is inso- 

 luble in alcohol. It parts with an atom of water when 

 heated ; its formula may then be BaO -f" C 20 H 7 ,S 2 O 4 . 



Naphtin-hyposulphuric acid or sulphonaphtic acid, HO 

 + C n H 4i O,S 2 O 5 , is not crystallizable, and very soluble in 

 water. 



Glutinhyposulphuric acid is separated from its salts by hydro- 

 chloric acid as a milky substance, which falls and collects 

 together in transparent, clammy drops ; its salts do not crys- 

 tallize. 



When naphtalirie is dissolved in excess by sulphuric acid, and 

 water added, the excess is precipitated, but in an altered state, 

 for when the precipitated naphtaline is distilled with water, it 

 leaves behind a fatty matter, from which alcohol separates two 



