i think maybe u saw this word from a chinese conversation..it means yes.yeah...蒽=恩=嗯 many chinese always type the wrong word..嗯 is right 我猜是别人给你发消息里有这个字吧，他应该说嗯，意思就等于yes.yeah.i agree with u.不过标准的是嗯。 恩和蒽是读音也和嗯一样，所以常常有人也用这两个字

If it is not use in the medical book or chemistry book, you must be find it on the internet. it is a kind of cyberword. just as the people above said 蒽=嗯，which means ok or yes.

It is just equal to "yeah".中国人聊天中经常把嗯，恩，蒽看成一样的，都是嗯的意思

正體中文字教學節目 中華電視台 新每日一字 http://vod.cts.com.tw/educ.php?pid=192

it doesn't need to have the meaning but because, you can just creat your own words.