80 



Sulpliobiitjric acid was hitlierto only known as a viscous liquid. 

 We succeeded in obtaining the acid in the crystallised state by 

 leaving a concentrated pure solution for a long time in vacuo over 

 phosphorus penloxide. 



The rf-sulphobiityric acid forms colourless hard crystals. Like 

 snlphoacetic and sulphopropionic acids it contains one molecule of 

 water of crystallisation and is extremely hygroscopic. The melting 

 point, determinated by the aid of a formely described apparatus'), 

 was found to be 66°. 



Since snlphoacetic acid melts at 84 — 85° and sulphopropionic acid 

 at J 00.5°, we have here perha|)S the beginning of an alternating 

 series of melting [)oints, as shown by the fatty acids. 



From Hulphobutyric acid we have prepared some salts with aromatic 

 amines. 



The acid sulphobutyrate of aniline forms small glistening crystalline 

 plates with the melting point 175". 



The acid sulphobutyrate of p-toluidine, which is separated by 

 ether from its alcoholic solution in the form of an ethergel, may 

 be obtained as a white crystallised substance of the melting point J 63°. 



The acid salts of [)-anisidiiie and p-phenetidine were obtained in 

 a crystallised state, but not pure and colourless. 



If these snlphobutyrates are heated with an excess of the coires- 

 ponding amines, the carboxyl group is changed into amide through 

 loss of water, the sulphonic acid group remaining combined with a 

 molecule of the amine. 



Ill this way aniline formed the butijraiul'ule-u-suIpJionic acid salt 

 of aniline 



(C,H.) (CONHC.HJ CH . SO,H . . . NH,C.H.. 



which crystallises from water in concentrically grouped featherlike 

 needles, occasionally 5 cM. in length, which melt at about 253° — 256°. 

 From the other above mentioned aromatic amines well ciyslal- 

 lised amides were also obtained, viz. 



butyro-p-tobü.dide-it-sulfonic acid salt of p-iolaidine, m.p. 260 — 263°, 

 butyro-p-anisidide-a-sulfonic acid salt of p-anisidine m.p. 242°, 

 hutyro-p-phenetidide-(t-snlfonic acid salt of p-phenetidive, m.p. 264—266°. 



When heated with aromatic o-diamines, sulphobutyric acid, just 

 as sulphopro|)ionic acid, loses two molecules of water and gives 

 derivatives of benzimidazole. 



The sulphobutyrate of o-phenylenediamine, for instance, formed 



1) Ghem. Weekbl. 16, 1564 (1919). 



