8 THE UNIVERSITY SCIENCE BULLETIN. 



In each case the following amounts of reagents were used and the 

 same procedure followed as exactly as possible: 



Aniline 26 gms. 



Carbon bisulphide 27 gms. 



Ammonium hydroxide (28%) 44 gms. 



Alcohol 20 CO. 



Lead nitrate 100 gms. 



The addition of the aniline required one-half hour. The stirring 

 was then continued for another one-half hour, and the mixture 

 filtered after standing for an additional hour. The separated salt 

 was dissolved in 200 cc. of water, treated with the lead nitrate (in 

 200 cc. water), and distilled with steam. The yield of pure mus- 

 tard oil was 20 gms. (53 per cent). 



In the second case the unfiltered solution and salt was made up 

 to 200 cc. with water and desulphurized as before. The product 

 weighed 28 gms. — a yield of 74.2 per cent, based on the aniline used. 

 The best yield obtained under these conditions was 76.8 per cent 

 pure phenyl isothiocyanate. The difference in yield in the above 

 experiments between 53 per cent and 74 per cent is due without 

 question to the solubility of the ammonium salt in the aqueous 

 ammonia. 



LABORATORY PREPARATION. 



The following directions are given as suitable for a laboratory 

 experiment in the preparation of the phenyl isothiocyanate: 



Place 54 grams of carbon bisulphide and 80 grams of cone. 

 NH4OH (28 per cent) in a tall beaker, surrounded by ice, and 

 stir the mixture with a turbine. Drop 56 gms. of aniline into this 

 mixture from a separatory funnel during the course of 20 minutes. 

 The separation of ammonium phenyl dithiocarbamate soon begins. 

 Continue the stirring for 30 minutes after all of the aniline has been 

 added. Then allow the mixture to stand for another period of 30 

 minutes without stirring. 



Dissolve the salt by the addition of 800 cc. of water, and add to 

 the solution (with constant stirring) 200 gms. of lead nitrate 

 dissolved in 400 cc. of water. Steam-distill the product from a 5- 

 liter flask. 



Put in the receiver a little dilute sulphuric acid ; this will combine 

 with traces of ammonia or aniline that might be driven over, and 

 thus prevent the formation of any mono- or diphenyl thiourea. 



