( 102 ) 



termediate occurrenco of acetal is iiii|»i'obable; we should then have 

 the reaction : « ^ aeetal :;± /?. The quantities measured being the velo- 

 cities with which « or ^ disappears and /? or a appears. It would 

 satisfy the formula for the reversible unimolecular transformations only 

 if the acctal was converted with an immeasurably great \elocity into 

 j3 or a. An attempt was made to elucidate this question by means of 

 a separate experiment. Supposing the mechanism of the transformation 

 to be really: 



«-glucoside ^ acelal ^ ji-glncoside 



we should then ha\'e two equilibrium reactions for which there would 

 exist four velocity constants. 



/i for «-glue. —5» aeetal, /,:\ for aeetal —> «-glue. 



A's II i^ II — ^ // /i-' -2 II II — ^ i' II 



As it had, however, been ascertained thai in the condition of equili- 

 brium, aeetal is practically absent, the liniil for the two equilibrium 

 reactions is situated close to the two gliicosides; from this follows 



Ic k ' 



that the ratios —and— must be very large. This is only possible if 

 k^ k^ 



k^ and k.^ are very small or in other words if the transformation, 

 setting out from either of the glucosides, proceeds very slowly, or 

 if k\ and k\ are very large, that is to say if the aeetal is converted 

 with extraordinary rapidity into the two glucosides. From the results 

 of the velocity determinations already given, it follows that the tirst 

 possibility does not exist; to test the secontl supposition, the non- 

 cry stallisable substance, which Fischer reservedly considered to be 

 the possible dimethylacetal of glucose was prepared according to his 

 directions. The syrup oI)tained by extraction with acetic ether was 

 lae\orotatory [it however still reduced Fehling's solution slightly] ; 

 it was dissolved in 2 n. methyl alcoholic hydrochloric acid (about 

 2,5 gr. in 25 c.c.m.) and the change at the ordinary temperature 

 was observed. This took place by no means rapidly. 



Rotation 



Everything considered it must be assumed to l)e very improbable that 

 the syrupy substance [perhaps the aeetal] occurs as an intermediate 

 product in the reaction /J- ^ «-glucoside. The traces of a syrup which 



