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(一)淀粉加水分解——①证明单醣产物(用二价铜还原为氧化亚铜);②证明有双醣中间产物“麦芽糖”。为了演示证明有灰醣(麦芽糖)这一实验,在很多书上是这样指导的,用淀粉加水在硫酸或盐酸的作用下,进行水解,在煮沸到一定程度不使碘酒变色时,用碳酸钙粉末以中和水解过程中的酸(有大量泡沫),然后过滤,除去硫酸钙(若CaCl_2不能去掉),再行蒸发掉糖浆中的水分,这一系列过程在课堂演示中因手续过繁,而浪费时间。最低需要一个多小时,我认为这祥演示可简化操作手续,时间只要30分钟左右。
(A) hydrolysis of starch - ① that monosaccharide products (with cuprous copper reduction to cuprous oxide); ② prove that the disaccharide intermediate “maltose.” In order to demonstrate the demonstration that there is a gray sugar (maltose) experiment, it has been instructed in many books that starch is hydrolyzed by the addition of water under the action of sulfuric acid or hydrochloric acid and, when boiled to a certain extent, does not discolor iodine, Calcium powder is used to neutralize the acid (with a large amount of foam) in the hydrolysis process and then filtered to remove the calcium sulphate (if CaCl 2 can not be removed) before evaporating the water from the syrup. , And a waste of time. The minimum required more than an hour, I think this demo can simplify the operation procedures, as long as 30 minutes.