[Varun gupta]

Please let me know the chemicals which change their color on reaction with oxygen after 2-3 days instead of spontaneous change

[Varun gupta]

Please let me know all the uses of caustic soda. Also tell me in which chemical production the same can be used

[Dan]

Your question is too broad, there are an enormous number of uses for NaOH.

http://en.wikipedia.org/wiki/Sodium_hydroxide

Please read the Forum Rules.

[Varun gupta]

Please let me know all the uses of soda ash.

[Varun gupta]

Thats what i want to know so that i can approach all the possible consumers

[sjb]

Please let me know all the uses of soda ash.

Compare the answer to your enquiry about sodium hydroxide, similar will apply here no doubt. Locked here.

[Arkcon]

Thats what i want to know so that i can approach all the possible consumers

I have merged all your questions into one thread, because your questions and responses will all end up the same anyway.  Please trouble yourself to read the Forum Rules, posted in Red, at the top of each page.  You have to begin with some knowledge, and ask specific questions.  No one will teach you everything, by typing it, once a day.  That's no way to learn anything.