■238 The Chninsh-ii of the Sfntif/f/' "J' W'/naf llmtr 



The above deteniiination.s wore carried out at least in duplicate and 

 the results were confirmed by independent investigation of further 

 samples of the two gliadines prepared from the same flours. 



It will readily be seen from the above data that the gliadines from 

 the two types of flour display throughout identical optical behaviour 

 when racemised by dilute alkali at 37°. This fact is brought out more 

 strikingly if the graphs representing the course of raceniisation be con- 

 structed. For each set of experimental conditions, it will be found that 

 one smooth curve can be drawn to satisfy equally the two sets of readings 

 for the Manitoba and English flour gliadines. Such slight discrepancies 

 as may occur fall within the general error of e.xperiment. 



When racemised by means of Nj'l NaOH, each gliadinc solution 

 possesses an initial s])ecific rotation of about — 114° (taken from graph ^). 

 The rotations of both solutions diminish fairly rapidly and at an equal 

 rate during the first 24 hours; tlie rate of diminution in each case then 

 falls off equally and after 240 hours, when the value of the rotation has 

 become practically constant, the two solutions possess an e(|ual specific 

 rotation of about — (57°. 



The presence of the small ainoujit of alcohol in the second series of 

 determinations e-xerts a striking elTec't on the rate of racemi.sation and 

 affects both gUadines in an equal degree. The effect is best studied by 

 constructing the graphs. The rate of racemisation during the first 

 24 hours for iV/2 NaOH is much quicker when alcohol is present than 

 when it is absent. In the presence of the alcohol, the specific rotation 

 during the first 24 hours sinks from — 114° to — 86°, whereas when no 

 alcohol is present, the corresponding diminution is from — 114° to about 

 — 97°. After about 50 hours, however, the two curves begin to come 

 together again and almost coincide after about 250 hours. The presence 

 of alcohol causes Nj^ NaOH to effect a greater reduction in specific 

 rotation during the first day than does iV/2 NaOH without alcohol. 

 These curves cro.ss after about .'}5 hours and from this point the rate of 

 diminution with the weaker alkali is relatively slow. The reason for the 

 effect thus produced by the alcohol, which resembles that of a catalyst, 

 requires further investigation. For the purposes of this enquiry, it is 

 sufficient to note that under the three different sets of conditions, the 

 gliadines from the weak and strong flours display the same optical 

 behaviour during racemisation. This fact is taken as evidence of the 

 identity of the two gliadines. A final test on a mixed sample of the two 



^ The graphs are init rrprnthu-ed lioro, as they are not necessary in enabling the 

 essential conehisions tu he drawn. 



