394 Hale —Initiative Action of Iodine and other 



Some pure erythrodextrin was made as follows : To 200 cmS 

 of a 1 per cent pure starch solution at a temperature of 40° C 

 was added 0*25 grm. of acid potassium carbonate and 10 cru3 of 

 filtered saliva. Not a trace of erythrodextrin, as shown by 

 testing with iodine every few minutes, appeared for twenty 

 minutes, and in thirty minutes the last traces of amidulin, as 

 shown by the iodine test, had disappeared. The solution was 

 at once boiled to stop further action of the saliva, and the 

 erythrodextrin was precipitated with three to four times its 

 volume of alcohol and filtered. The precipitation was only 

 partial and filtration was very slow. The erythrodextrin, 

 washed with alcohol, was redissolved in 200 cm3 of warm water. 



Both of these solutions were tested by the polariscope for 

 rotation of polarized light. Of each solution ten readings were 

 made with the sodium flame and the average was taken. The 

 percentage strength of the solution was determined in two dif- 

 ferent ways. In the case of the erythrodextrin by saliva diges- 

 tion, 25 cm3 portions were drawn from a burette into weighed 

 beakers and evaporated to dryness over sulphuric acid in a 

 vacuum dessicator. Duplicates gave 0-0422 and 0*0424 grm. 

 of dextrin. Hence 100 cm3 contained 0-1692 grm. of erythro- 

 dextrin. The readings with the polariscope were all very close 

 and gave a result of 0'26°-K As a i dcm tube was used 



<•>->- Kjolesr 158 ' 66 ° + - 



A previous attempt was made to precipitate the dextrin by 

 alcohol and ether and to filter on a Gooch crucible, but it failed 

 of complete precipitation. 



A slightly different course was taken with the dialyzed 

 erythrodextrin, as the above method was rather long and 

 tedious. As a preliminary test, portions of the erythrodextrins, 

 dialyzed and by saliva, were evaporated to dryness on the 

 water bath. No change seemed to have taken place. Both 

 preparations were just as soluble as before evaporation and 

 gave a rich red with iodine. Hence 25 cm3 portions of the dial- 

 yzed dextrin were drawn from a burette into small weighed 

 porcelain dishes and evaporated to dryness. In this way the 

 percentage strength of the solution was found to average 

 0-0716 grm. per 100 cm3 . The readings with the polariscope 

 were again very close and gave 0-22° + . As a 2 dcm tube was 



22 

 used (<)d = . 000 ' 716v2 = 153-63°'+. The degree of rotation is 



so close to that of the saliva digested starch product that the 

 identity seems certain. 



That the loss of iodine in titration is due to the formation 

 of erythrodextrin from amidulin and not achroodextrins from 

 erythrodextrin is shown by the following experiments : 



