SN'N'i"iii-:sis ()i i)i:i'sii)i".s. 141 



W liicli CDiuhiiK's willi i^lycin ester, tonninj^ 



/O.COOCIl, 

 (d) C,H, 



"- CO. Xll. ell,. C( )UC.,I[, 



which, with dilute alkali and .siihseiiuciitly acid, yields — 



y OH 



(c) C,H, 



^ CO. Xll. CI I,. COOil 



Para-hydroxy-hii)i)uric acid. 



Similarly, in the case of the i)lienol-carboxylic acids them- 

 selves, union takes place between the ()1I and CO( )H groups; 

 thus — 



/O. COOCH;, [. X OXa I. 



C,H, with C,llj 



^ COCl 4. \ COONa 4. 



yields 



/ O.C( )OCti.> I. 



■^ CO. O. C,Fl,. COONa 4. 



which, with alkali and then acid, as above, yields 



/ Oil I. 



C,,H, 



^ CO. O. C.ll,. COOH 4- 



This is the simplest type o.f a new series of substances which 

 have been named by Fischer the depsides, from the Greek word 

 8e-\}r€tv to tan, since many of these substances possess properties 

 similar to the tanning materials in common use. From this sub- 

 stance and i).-h\'droxy-ltenz()ic acid is obtained in a similar ukui- 

 tier — 



/Oil 



QH, 



"^ co.o. c„iu co.o.c.H, coon 



and so on. According to the nr:;nl)er of i)henol carboxylic acids 

 coupled together, we distinguish between di-. tri-, tetra-. dep- 

 sides, just as in the case of the polysaccharides and i)olypei)tides. 

 Up to 1913. Professor Fischer had prepared, in a state of purity, 

 28 di-depsides, 2 tri- and 2 tetra-depsides. 



These substances are Ijy no means new. a few ol the simpler 

 ones having been prepared formerly. H. Schiff and others pre- 

 pared from gallic acid, by means of silver nitrate or arsenic acid, 

 and then phosphorus oxychloride. a substance to which the name 

 diffallic acid was given.' and fornnila CuHi,/).,. supposed to be 



