题干

亚甲基蓝(Methylnene Blue)在碱性条件下与葡萄糖作用生成亚甲基白(Methylene White).亚甲基蓝的结构简式:


著名的蓝瓶子实验操作步骤如下:


①如图示在250mL锥形瓶中,依次加入2g NaOH、100mL H2O和3g葡萄糖,搅拌溶解后,再加入3滴~5滴0.2%的亚甲基蓝溶液,振荡混合液呈现蓝色;

②塞紧橡皮塞(活塞a、b关闭),将溶液静置,溶液变为无色;

③再打开瓶塞,振荡,溶液又变为蓝色;

④再塞紧橡皮塞,将溶液静置,溶液又变为无色.以上③、④可重复多次.

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    Speaking English is not only about using proper grammar.To use English effectively,you need to understand the culture in which it is spoken.Here are a number of important tips to remember when speaking English in the United States.

    Conversation tips.

    Talk about location____When speaking to strangers,ask them where they are from and then make a connection with that place.For example:“Oh,I have a friend who studied in Los Angeles.He says it's a beautiful place to live in.”  Most Americans will then willingly talk about their experiences living or visiting that particular city or area.

    Talk about work____It's not considered impolite and is a popular topic of discussion between strangers.

    Talk about sports.Americans love sports!____When speaking about football,most Americans understand “American Football”,not soccer.

    ____ Many Americans prefer first names.Americans often prefer using first names,even when dealing with people in very different positions.Americans will generally say,“Call me Tom.”and then expect you to remain on a first name basis.

    Public behavior.

    Always shake hands.____This is true for both men and women.Other forms of greeting such as kissing on the cheeks is generally not appreciated.

    Smoking is out!Smoking,even in public places,is strongly disapproved of by most Americans in the modem United States.

A.Addressing people.

B.Talking with people.

C.However,they love American sports.

D.Americans love to talk about location.

E.Americans commonly ask “What do you do?” .

F.Americans prefer to make friends with foreigners.

G.Americans shake hands when greeting each other.