ACID QUESTION

Please excuse this question; I realize this must seem elementary but I am quite stymied and it entails a work related situation.
Cleaning out a acid cupboard where I work there are several bottles of technical grade HNO3 which would be approx 70% but there are others which are marked as "Fuming" (current date). My question is does there exist a simple method to determine the percentage of acid if no specific gravity info is present (i.e. 1.43, 1.50. etc, etc) ?
There are some other bottles that are student's from last semester that have a variety of information dealing with temp...can HNO3 be "cooked" to a higher percentage (exposed to heat, thus reducing the water content? I was told that under no circumstances to get rid of the higher percentage grades as they cost quite a bit more money. But if they can be reduced, why pay for a higher percentage? I am quite aware of the "kitchen" methodologies of extraction w/ methylene chloride and destilation but I always wondered why a higher percentage was simply not produced via evaporation?
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