270 Intelligetice and Miscellaneous Articles. 



heat, anhydrous chloride of chromium with chloride of potassium.^ 

 Ann. de Ch. et de Phys., December 1 844. 



ON HEMIPINIC ACID. BY M. WOHLER. 

 This is the product of the oxidizement of opianic acid. It is pre- 

 pared with difficulty, because it is destroyed by the same irvfiuences 

 as those by which it is produced. It is obtained as follows : — heat 

 together to ebullition opianic acid and peroxide of lead, then drop 

 gradually into the mixture sulphuric acid to disengage carbonic acid. 

 A small quantity of the liquid is then to be allowed to cool, and a 

 sufficient quantity of sulphuric acid is to be added to precipitate all 

 the lead which has been dissolved ; filter and evaporate the solution. 

 It often happens that the crystals first obtained are opianic acid, 

 which are however easily separated from the hemipinic acid by cry- 

 stallization, the latter being much more soluble ; peroxide of lead 

 alone does not act upon opianic acid. 



Hemipinic acid crystallizes very readily in colourless oblique four- 

 sided prisms ; it has a slightly sour and astringent taste, and dis- 

 solves readily in cold water. The solution has a strong acid reac- 

 tion ; alcohol dissolves this acid readily ; the crystals exposed to 2 1 2° 

 lose 13*73 per cent., or two equivalents of water. The effloresced 

 acid fuses at 356° and becomes a crystalline mass on cooling ; when 

 heated between pieces of glass, it sublimes like benzoic acid in bril- 

 liant laminae ; it burns with flame, and when heated with peroxide of 

 lead and sulphuric acid, it appears to be entirely converted into car- 

 bonic acid and water ; with ammonia it forms a readily soluble cry- 

 stallizable salt, which is unalterable in the air. The salts of silver and 

 lead are white and insoluble ; the latter is soluble in acetate of lead, 

 and separates later from solution in mammillated crystals. 

 , This acid, after exposure to 212°, yielded by analysis, 



Experiment. Equivalents. Calculation. 



Carbon 5294 10 5314 



Hydrogen.. 4*65 5 4*41 



Oxygen . . 42-41 6 42-45 



100- 100- 



The salt of silver was found to consist of — 



Equivalents. Calculation. 



Carbon 27-19 10 27-28 



Hydrogen 1-83 4 1-81 



Oxygen 18-10 5 18-18 



Oxide of silver . . 52-88 1 5273 



100- 100- 



Hemipinic acid is then represented by the formula 0'° H** O^ ; the 

 .effloresced acid contains one equivalent of water, which is separable 

 by bases =H + C»oH'*0*. 



One equivalent of opianic acid plus one equivalent of oxygen form 

 two equivalents of hemipinic acid. It contains as its radicle half of 

 the radicle of opianic acid, and hence the name of hemipinic acid. 

 The author obtained this acid also by directly acting upon narco- 



