39 



acid. It dissolves potassium in the cold and zinc on heating with 

 the evolution of hydrogen, and gives with lead a salt less soluble 

 than the ordinary acetate, so that it gives a precipitate with acetate 

 of lead. By recrystallization from water or alcohol, the lead salt is 

 obtained in fine silky needles, which, though quite colourless at first, 

 are rapidly decomposed (whether in solution or in the solid form) 

 with the formation of sulphide of lead. 



By analysis I found the lead salt contained 



Lead 5 8 '8 per cent. Theory requires 58'0 per cent. 



The acid contained 



Sulphur 41 '3 per cent. Theory requires 42' 1 per cent. 



Thiacetic acid is also formed in small quantity and by secondary 

 action, by distilling pentasulphide of phosphorus with fused acetate 

 of soda. Pentachloride of phosphorus gives a violent reaction with 

 thiacetic acid, yielding sulphochloride of phosphorus, chloride of 

 othyl, and hydrochloric acid. 



Thiacetate of Othyl. Sulphide of Othyl. Anhydrous Sulphuretted 

 Acetic Acid. Pentasulphide of phosphorus acts but very feebly upon 

 anhydrous acetic acid in the cold, but on heating a violent reaction 

 takes place. By distilling the product, the anhydrous acid is obtained 

 in the form of a colourless liquid, boiling at about 121 C., and having 

 an odour greatly resembling sulphuretted acetic acid. On mixing 

 with water it falls to the bottom, without, at first, suffering any 

 change ; on standing, however, it is slowly dissolved and decom- 

 posed into sulphuretted acetic acid and ordinary acetic acid. This 

 change takes place much more rapidly on heating, 



CIT f\~\ 13 ~\ f~< TJ f~\~\ /~< U f\ ~\ 



2 rlj \J I C I " I O ^2 -"3 I C _L_ 2 *~*3 LCI 



C 2 H 3 Oj ^J ** J *^ / 



It appears that anhydrous sulphuretted acetic acid is also pro- 

 duced by acting on the othyl-sulphide of lead with chloride of othyl, 

 at all events chloride of lead is formed. Chloride of benzoyle gives 

 with the lead salt a similar reaction, and it is probable that an inter- 

 mediate sulphuretted acid is formed, having the formula 



C, H, O 



