โ Scribed by Mack, Charles
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.U.~CK--~TCIIP UP UlTUWISoL!S JIIXTORES ON ROAD-TESTIS0 JIAC~I~SES 111 (0.040 g./100 c.c.). The results obtnined are given in Tnhle VI. CONCLUSIONS (1) The visibie pert of the absorption spectrum (4300-7500 A.) of the starch-iodine complex is most sensitive to the depolymerisation of the stnrch.
(2) Increasing the ratio of iodine to starch causes the absorption of the stnrch-iodine spectrum to increase considerably (espwinlly in the visible pnrt of the spectrum), without appearing to reach a Limiting figure even nfter allowance hns been madc for the increased absorption of the iodine-iodide present. IIence the ahsorption of the starch-iodine complex (and presumably also its composition) appears to depend on both the relative and nctual proportions 'of starch and iodine-iodide present in solutiou.
(3) Correlntion of the results obtnined in the present investigation with the effects of amylase nction on the absorption spectra of the stnrch-iodine comples12 leads to the conclusion that the grinding of whent starch in a hnll mill for 7000 hours results primarily in the rupture of the " luternl linknges " thnt bind together the repcating units in the starch mncromolecule, without brenkdown to any significant degree of the repeating units tliemselveu.
(4) The rupture of the "loteral linknges" in the starch muoromolecules causes the starch-iodine spectrum to decrense in ahsorption in the longer visihle mve-lengths.
(5) Tho characteristies of tho nbsorption spectrum of the stnrch-iodino and dextrin-iodine complexes appear to depend both on the molcculnr weight and 011 the length of the repeating units of the starch or dextrin.
The fnct that depolymerisation of C.W. Sol. starch from ti mean molecular weight of 33,000 to 5550 nlters the main characteristics of the stnrch-iodine absorption spectrum much less than does brookdon-n to dextrins by nppenrs to be evidence that the ahsorption spectrum is ntoro dependent on the length of the repeating units than on the moleculnr weight.
(6) The absorption spectra givcn hy iodine with thc sninll qunntity of material extractable from unground starches by cold water confirm tho previous conclusions2 that this matcrinl is composed of a small proportion of " soluble starch," a mixture of dertrins, and possibly sonic simple reducing sugars.
The authors wish to thunk Jfiss D. Y. Rrnshcr, who cnrried out the spectrographic work involved, und i l k P. Bilharu for critical ohscrvatione, and nlessrs. J. Lyons & Co., in whose Laboratories this work has been carried out, for their pertuission to publish.
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