ACETIC ACID. 87 



Thiacetic acid, C 2 H 4 OS = CH 3 .CO.SH, is produced 

 by distilling concentrated acetic acid with phosphorus 

 tersulphide or pentasulphide. Colorless liquid, which 

 turns yellow when left for any length of time ; smells 

 of acetid acid and sulphuretted hydrogen ; boils at 93 ; 

 and is soluble in water and in alcohol. Its salts are 

 soluble in water. 



The lead salt, (C 2 H 3 O.S) 2 Pb, forms colorless needles, 

 which are decomposed easily, sulphur being thrown 

 down. 



Acetic anhydride, (C 2 H 3 0) 2 0, is obtained by dis- 

 tilling 3 parts anhydrous sodium acetate and 1 part 

 phosphorus oxichloride; or, better, by distilling equal 

 parts by weight of acetyl chloride and anhydrous 

 sodium acetate. Colorless liquid, boiling at 138, 

 heavier than water, decomposed rapidly by it, forming 

 acetic acid. With hydrochloric acid it yields acetic 

 acid and acetyl chloride; with chlorine, monochlor- 

 acetic acid and acetyl chloride. Bromine acts the 

 same as chlorine. Phosphorus sulphide converts it into 

 thiacetic anhydride (C 2 H 3 0) 2 S, a yellowish liquid, boiling 

 at 121. 



Acetyl hyperoxide, (C 2 H 3 0) 2 2 , is obtained by 

 adding barium peroxide to an ethereal solution of 

 acetic anhydride. After distilling off the ether at a 

 very low temperature, washing with water and potas- 

 sium carbonate, it remains as a thick, consistent liquid. 

 Is rapidly decomposed in sunlight; explodes when 

 gently heated, like nitrogen chloride. Powerful oxi- 

 dizing agent, decolorizes indigo, separates iodine from 

 potassium iodide, and converts potassium ferrocyanide 

 into the ferricyanide. 



Acetyl chloride, C 2 H 3 O.C1 = CH 3 .COC1, is formed 

 when dry hydrochloric acid gas is allowed to act upon 

 acetic acid in the presence of phosphoric anhydride; 

 by the action of phosphorus terchloride, pentachloride, 

 or oxichloride on acetic acid or dry acetates. Is most 

 readily prepared by carefully distilling a mixture of 9 



