LITHOFELLIC ACID. 117 



in a crystalline form, if it has not been too highly heated ; 

 if, however, this has been the case, it solidifies into a 

 vitreous, negatively idio-electric mass ; in this condition it fuses at 

 105 to 116; by solution in, or mere moistening with, alcohol, it 

 returns to its former condition, being difficult to fuse again ; when 

 heated in the air, it volatilises in white vapours with an aromatic 

 odour ; when inflamed it burns with a bright, smoky flame ; it is 

 decomposed by dry distillation ; it is insoluble in water, dissolves 

 readily in hot alcohol, but only slightly in ether; acetic acid 

 dissolves it freely ; acids precipitate it from its soluble salts as an 

 amorphous coagulum. 



Composition. Ettling and Will,* from their analyses, calculated 

 for it the formula C 42 H 36 O S ; W6hler,f from his analyses, deduced 

 the formula C 40 H 3G O 8 ; and Berzelius,J judging from the saturating 

 capacity of the acid, considers the formula C 40 H 36 O 7 .HO as the most 

 correct : hence it must be regarded as containing : 



Carbon 40 atoms .... 70-381 



Hydrogen .... 36 .... 10'557 



Oxygen 7 .... 16-422 



Water 1 .... 2-640 



100-000 



Hence the atomic weight of the hypothetical anhydrous acid 

 (according to the above formula) =4150, and its saturating capacity 

 = 2-41. 



Combinations. This acid dissolves readily both in caustic 

 ammonia and in carbonate of ammonia, but on evaporation of the 

 solution it remains free from ammonia ; the salts of baryta and 

 lirne throw down no precipitate from this solution : moreover, it 

 dissolves readily in caustic potash, but is precipitated by an excess 

 of potash as well as hy hydrochlorate of ammonia; on the addition 

 of the salts of lead or silver to a saturated potash-solution of this 

 salt with only a faintly alkaline reaction, there is a white precipi- 

 tate which, on warming, becomes plaster-like. Ettling and Will 

 have obtained a silver-salt which crystallised in needles ; Wohler, 

 however, only obtained an amorphous salt. 



Preparation. This acid, which was originally discovered by 

 Gobel, is extracted from certain intestinal concretions by hot 



* Ann. d. Ch. u. Pharm. Bd. 39, S. 237-244. 



t Pogg. Ann. Bd. 54, S. 255. 



t Jahresber. Bd. 22, S. 580. 



Ann. d. Ch. u. Tharm. Bd. 39, S. 237. 



