Starch with acrolein

Although they lack commercial importance, many other poly(vinyl acetal)s have been synthesized. These include acetals made from vinyl acetate copolymerized with ethylene (43—46), propjiene (47), isobutjiene (47), acrylonitrile (48), acrolein (49), acrylates (50,47), aHyl ether (51), divinyl ether (52), maleates (53,54), vinyl chloride (55), diaHyl phthalate (56), and starch (graft copolymer) (47). 

S - of the substance to be analysed is placed in a small glass bulb which is then sealed in the blowpipe and weighed. The bulb is placed in a bottle together with 100 ml. water. The bulb is then broken and a standardised solution of sodium bisulphite added, sufficient being employed to react with 50% more acrolein than is actually present in the sample. The mixture is allowed to stand for about 6 hours and then the excess of bisulphite is titrated with iodine solution in presence of starch, to a blue coloration stable for 15 minutes. 

---