โ Scribed by Fairs, C. L.
No coin nor oath required. For personal study only.
Imth of sufficicnt nlcohol nnd of n smnll qunntity of electrolyte to prccipitntc completely thc dissolved stnrch. In this t h y bclinrc similnrly to the nqueous solutions of other lipdrophilic cnrbohpdrntc colloids of relatively high moleculnr wight.
(2) Drying stnrcli frnctions hns been fouud to be nccompnnied by n loss in solubility in wnter. The cxtcnt of the resulting " insolubilisntiou '' lins becn found to depend, inter nliu, on tlic method of drying used nnd to be govcrucd by the riiolcculnr wciglits of tlic frnctions.
(3) Evnporntion of stnr'ch solutions on n wnter-bnth, folloived l)p drying n t 100' in tucuo, nppenrs t o cnuse n grcnter clegree of iiisolubilisntion tliiin tloes prccipitntion by nlcoliol, folloivcd by further tlcliytlrntion first by nlcoliol, tlicii bp cthcr, itiitl finnlly by nir-(Iryiug n t room tenipcrnture. Tlic former method cniisrs both tlic C.W. Sol. and the H.W. Sol. frnctions to IJCCOIIIC insolubiliscd, whcrcns the lnttcr method iusolubilises only the H.W. Sol. frnctions (ivhicli Iinve II higlier nienn inolccnlnr wiglit thnn the corresponding C.W. Sol. frnctions).
(4) The belinriour of solutions of potnto nnd alirnt stnrcli ,%nmyloscs on drying by the nictliods tlcscribcd in (3) is siniilnr to thnt of tlic solutions of the H.W. Sol. fractions, thus iiidicnting thnt the H.\'. Sol. frnctions correspond with the so-culled /3-omylosc fraction of stnrch.
(5) Evidence esists in the litcrature that mnny Iiydrophhc colloids of considcrnble molecular weight are " insolubiliscd " on being dried and there nrc iudicntions thnt, as in the cnsc of stnrch, the cstcnt of the iiisolubilisntiou depcnds on the rnethod of drying used, niid on the inenn niolcculnr \veiglit of the colloid.
(6) The flocculntion of tlic H.W. Sol. frnctions by addition of nlcohol appcnrs to cause a ccrtniii nmount of dcpolymerisntion in the stnrch.
(7) Further evidcncc hns bccri obtained of the nbnormnlity of the H.W. Sol. 470 fraction of grouud whcnt stnrch ns conipnred with the otlicr H.W. Sol. frnctions.
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