62 



Mr. E. A. Letts on a new Method [Dec. 5, 



analogous to that observed with the phenyl mustard-oil, it was to be 

 expected that 1 molecule of this body would react with 3 molecules of 

 acetic acid to produce 1 molecule of potassium acetate and 1 molecule of 

 diacetamide, carbonic anhydride and sulphuretted hydrogen being evolved. 



KCNS + 3(C 2 H 3 . OH) = C 2 H 3 O . OK + (C 2 H 3 0) 2 HN + C0 2 + H 2 S. 



The reaction, however, takes a different course. 



In my first experiments the acetic acid was allowed to react on the 

 sulphocyanate under pressure ; but it soon became evident that this was 

 unnecessary, simple digestion of the two bodies in a flask provided with 

 an upright condenser being amply sufficient. 



The powdered salt dissolves readily in the boiling acid, and an imme- 

 diate and copious disengagement of gas ensues, in which carbonic an- 

 hydride and sulphuretted hydrogen may be readily recognized. Con- 

 siderable time, however, elapses before the sulphocyanate is completely 

 decomposed, some three or four days being required for a mixture of 

 100 grms. of potassium sulphocyanate and 180 grms. of acetic acid. At the 

 end of this time the products of the reaction were submitted to distilla- 

 tion and commenced boiling at 170°-180°; the thermometer, however, 

 rose rapidly to 216° ; and between this temperature and 220° the distil- 

 late solidified in. the receiver to a radiating crystalline mass, which ana- 

 lysis showed to be pure acetamide*. Above 220° nothing further distilled, 

 the residue in the retort consisting wholly of potassium acetate. In 

 what manner had acetamide been formed, instead of diacetamide ex- 

 pected in the reaction ? It appeared not unlikely that the acetic acid 

 employed contained some water, and that the diacetamide produced in 

 the first instance was thus converted into the monocompound — 



<P> H 3 0) 2 1 N + n 2 0=C 2 H 3 O . OH + C ^3 O | N . 



To remove any water which might possibly have been present, the 

 acetic acid was treated with phosphoric anhydride, and the experiment 

 with the sulphocyanate repeated ; but even now acetamide was exclusively 

 obtained. 



On submitting, however, the gases evolved during the reaction to a 

 closer examination, the formation of acetamide became at once intelligible. 

 It was found that a large proportion of these consisted of carbonic 

 oxysulphide (COS). To prove the presence of this compound, it was 

 only necessary to pass the evolved gases through a bottle containing a 

 slightly acid solution of lead, by which the sulphuretted hydrogen was 

 retained : thus purified, they produced no further precipitate when passed 

 through a second bottle containing the same solution ; but precipitation 

 at once took place if this were rendered alkaline by soda or ammonia. 



* The liquid products passing over before 216° yield considerable quantities of the 

 amide on fractionation ; the same remark applies to the other experiments with the 

 fatty acids to be presently described. 



